c# tutorial - simple threaded tcp server - tech.pro

C# Tutorial - Simple Threaded TCP Server - Tech.Pro

http://tech.pro/tutorial/704/csharp-tutorial-simple-threaded-tcp-server[07.06.2013 15:54:59]

C# .NET 2.0 Brandon Cannaday posted 5 years ago K

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C# Tutorial - Simple Threaded TCP Server

In this tutorial I'm going to show you how to build a threaded tcp server with C#. If you'veever worked with Window's sockets, you know how difficult this can sometimes be.However, thanks to the .NET framework, making one is a lot easier than it used to be.

What we'll be building today is a very simple server that accepts client connections and cansend and receive data. The server spawns a thread for each client and can, in theory,accept as many connections as you want (although in practice this is limited because you

can only spawn so many threads before Windows will get upset).

Let's just jump into some code. Below is the basic setup for our TCP server class.

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using System;using System.Text;using System.Net.Sockets;using System.Threading;using System.Net;

namespace TCPServerTutorial{ class Server { private TcpListener tcpListener; private Thread listenThread;

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So here's a basic server class - without the guts. We've got a TcpListener which does a good job of wrappingup the underlying socket communication, and a Thread which will be listening for client connections. You mighthave noticed the function ListenForClients that is used for our ThreadStart delegate. Let's see what that lookslike.

This function is pretty simple. First it starts our TcpListener and then sits in a loop accepting connections. Thecall to AcceptTcpClient will block until a client has connected, at which point we fire off a thread to handlecommunication with our new client. I used a ParameterizedThreadStart delegate so I could pass the TcpClientobject returned by the AcceptTcpClient call to our new thread.

The function I used for the ParameterizedThreadStart is called HandleClientComm . This function is responsiblefor reading data from the client. Let's have a look at it.

public Server() { this.tcpListener = new TcpListener(IPAddress.Any, 3000); this.listenThread = new Thread(new ThreadStart(ListenForClients)); this.listenThread.Start(); } }}

private void ListenForClients(){ this.tcpListener.Start();

while (true) { //blocks until a client has connected to the server TcpClient client = this.tcpListener.AcceptTcpClient();

//create a thread to handle communication //with connected client Thread clientThread = new Thread(new ParameterizedThreadStart(HandleClientComm)); clientThread.Start(client); }}

private void HandleClientComm(object client){ TcpClient tcpClient = (TcpClient)client; NetworkStream clientStream = tcpClient.GetStream();

byte[] message = new byte[4096]; int bytesRead;

while (true) { bytesRead = 0;

try

http://msdn2.microsoft.com/en-us/library/system.net.sockets.tcplistener.aspx

http://msdn2.microsoft.com/en-us/library/system.threading.thread.aspx

http://msdn2.microsoft.com/en-us/library/system.threading.parameterizedthreadstart.aspx

http://msdn2.microsoft.com/en-us/library/system.net.sockets.tcpclient.aspx



The first thing we need to do is cast client as a TcpClient object since the ParameterizedThreadStartdelegate can only accept object types. Next, we get the NetworkStream from the TcpClient, which we'll beusing to do our reading. After that we simply sit in a while true loop reading information from the client. TheRead call will block indefinitely until a message from the client has been received. If you read zero bytes from

the client, you know the client has disconnected. Otherwise, a message has been successfully received fromthe server. In my example code, I simply convert the byte array to a string and push it to the debug console.You will, of course, do something more interesting with the data - I hope. If the socket has an error or the clientdisconnects, you should call Close on the TcpClient object to free up any resources it was using.

Believe it or not, that's pretty much all you need to do to create a threaded server that accepts connections andreads data from clients. However, a server isn't very useful if it can't send data back, so let's look at how tosend data to one of our connected clients.

Do you remember the TcpClient object that was returned from the call AcceptTcpClient? Well, that's the objectwe'll be using to send data back to that client. That being said, you'll probably want to keep those objectsaround somewhere in your server. I usually keep a collection of TcpClient objects that I can use later. Sendingdata to connected clients is very simple. All you have to do is call Write on the the client's NetworkStreamobject and pass it the byte array you'd like to send.

Your TCP server is now finished. The hard part is defining a good protocol to use for sending informationbetween the client and server. Application level protocols are generally unique for application, so I'm not goingto go into any details - you'll just have to invent you're own.

{ //blocks until a client sends a message bytesRead = clientStream.Read(message, 0, 4096); } catch { //a socket error has occured break; }

if (bytesRead == 0) { //the client has disconnected from the server break; }

//message has successfully been received ASCIIEncoding encoder = new ASCIIEncoding(); System.Diagnostics.Debug.WriteLine(encoder.GetString(message, 0, bytesRead)); }

NetworkStream clientStream = tcpClient.GetStream();ASCIIEncoding encoder = new ASCIIEncoding();byte[] buffer = encoder.GetBytes("Hello Client!");

clientStream.Write(buffer, 0 , buffer.Length);clientStream.Flush();

http://msdn2.microsoft.com/en-us/library/system.net.sockets.networkstream.aspx



But what use is a server without a client to connect to it? This tutorial is mainly about the server, but here's aquick piece of code that shows you how to set up a basic TCP connection and send it a piece of data.

The first thing we need to do is get the client connected to the server. We use the TcpClient.Connect method todo this. It needs the IPEndPoint of our server to make the connection - in this case I connect it to localhost onport 3000. I then simply send the server the string "Hello Server!".

One very important thing to remember is that one write from the client or server does not always equal oneread on the receiving end. For instance, your client could send 10 bytes to the server, but the server may notget all 10 bytes the first time it reads. Using TCP, you're pretty much guaranteed to eventually get all 10 bytes,but it might take more than one read. You should keep that in mind when designing your protocol.

That's it! Now get out there and clog the tubes with your fancy new C# TCP servers.

Post a Comment

Comments (294)Viswanathct posted 6 years agoI searched a lot for a simple article in tcp reading / writting.

After googling with several alternatives i found this page.

Simply Good & simple.

Thx.

Anonymous 4 years ago

TcpClient client = new TcpClient();

IPEndPoint serverEndPoint = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 3000);

client.Connect(serverEndPoint);

NetworkStream clientStream = client.GetStream();

ASCIIEncoding encoder = new ASCIIEncoding();byte[] buffer = encoder.GetBytes("Hello Server!");


http://msdn2.microsoft.com/en-us/library/system.net.ipendpoint.aspx

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Check MSDN they have a great example.

bst78 3 years agoPlease show me the microsoft's example. This example is very very good!

If you mean the example with server and "dummy" remote server object(http://support.microsoft.com/kb/307445) I can not agree with you :-)

Anonymous 3 years agoVery thnx. Excellent. I learned tcp from here...

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Mas-Tool posted 6 years agoYep, it's very simple if you're writing a console application. Try making a chat with with .NET sockets andyou'll figure out there are no events support :-/ unlike VB6 with Winsock :)

Brandon Cannaday 6 years agoCan you elaborate on the events support? A few years ago a couple of us built a simple chatapplication using the framework above without any issues.

Mas-Tool 6 years agoHi again :) Well, if you need to make a chat like application you have to use a non-blocking socketsright ? so you use async methods (BeginReceive/EndReceive BeginConnect/EndConnect etc) but theproblem is the once you received some data or got connected, you're AsyncCallback is fired andyou're on a seperate thread ! so you have to Invoke the mothods for the GUI's thread to know you'vereceived some data :-/ But how can you invoke a method if you're a "pure" class and not a control witha parent control to call the Invoke method?

That's the way i see it, but maybe I'm wrong :) I'de like to know what you think!

Mas-Tool

Brandon Cannaday 6 years agoI don't really like using the Async callbacks so I opted for a blocking socket sitting on its own thread.When a message was received, I would then fire an event out of the "pure" class that can be caughtby a higher level control. My event handler would contain the message that was received. The controlwould then invoke a method to display the message to the GUI.

That's the architecture I like to follow, but of course it won't work for every application.

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Martijn Dwars posted 6 years agoA little parse error in your client program:

Needs to be:

IPEndPoint serverEndPoint = new IPEndPoint(IPAddress.Parse("127.0.0.1", 3000);

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Brandon Cannaday 6 years agoGood catch. I've corrected the post.

suresh kallem one year agoIm new to TCPIP programming, please help me sort out the following problem,

i have once server and many clients(around 500 numbers). client system connected to the manyhardware devices. server have to monitor client systems status, connected devices and its status andmany other operations. here client should send their status to server for every interval of time andserver should display it.

please suggest me on the same.

David posted 6 years agoVery good tutorial. clear and simple. thanks a lot

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AnilKumarVerma posted 6 years agoI am searching for windows version of it,it is too simple for beginers

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Some posted 6 years agoAnybody know how to connect via internet? PC1->routerA->internet->routerB->PC2

Anonymous 3 years agoIn this case i expect that you have to make sure that your routers are properly configured. Dependingon the type of your router you may have to use the "Port forwarding" of protocol TCP @ your portused by your application.

e.g. application uses port 3000 then routerA will need to forward incoming TCP connection on port3000 to your PC1. Secondary routerB will need to be configured to forward incoming TCP connectionson port 3000 to PC2.

additionally any firewall has also to be "pinned" @ port 3000 so that your application can talk throughthe whole "IP-devices-chain"

i tried this a few months ago with an cellphone via IP-network to an Windows PC behind NAT and itworked fine about nearly that way. (PC->router->internet->cell-network->cellphone GPRS channel)

sevket 6 months agoI want to learn your application. Could you please share your experience with me?

Manish posted 6 years agois there a simple version of this for .net 1.1? specifically with regards to closing the connection releasing clientresources to be able to use them again, the next time a connection comes in...

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Tony posted 6 years agoIs there a particular reason for starting a thread in the constructor? As far as I can tell there would be nodifference just calling ListenForClients() and it creates its own threads.

Brandon Cannaday 6 years agoListenForClients is going to block whatever thread calls it while it listens for client connections. Most ofthe time, my Server class is created on the main thread. I don't usually want to block my main threadwhile waiting for connections, so I created another thread which can be blocked without affecting therest of my application.

Working Class Hero posted 6 years agoWhen I close my win forms serverapplication (in debug state) it does not kill that thread. So what should I do?How I kill that clientThread and listenThread?

Brandon Cannaday 6 years agoFor the clients, you'll want to call Close on their NetworkStreams. This will cause the read to unblockand throw an exception which will be caught by the exception handler (which breaks out of the loop,ending the thread).

On the TcpListener, you'll have to call Stop. I'm not sure exactly what this will do to the blockingAcceptTcpClient call. It will either unblock and return null, or it will throw an exception. Either way,you'll want to stick in some error handling. When the error is caught, simply break out of the listenloop.

Working Class Hero 6 years agoYES! it worked! yippee thanks a lot!

Pc_Madness posted 6 years agoSorry to be the newb.. but does someone have/know of an example of how to get data to and from the classto a form? :(

*sigh* I had an awesome idea for a program, but can't actually make a start on it cos I have to get this TCPstuff out of the way and I have no idea whats going on. :( I miss Winsock.. now that was simple. :)

Brandon Cannaday 6 years agoIf by "the class" you mean the TCP server class, then it's not too hard. Inside the HandleClientCommthread, fire an event with the data that can be caught by your Form.

Depending on how much information you need, you might want to also pass the TcpClient throughyour event as well. For a tutorial on custom event handlers, check out this post.

Now all you have to do is hook the event from your form.

public delegate void MessageReceivedHandler(string message);public event MessageReceivedHandler MessageReceived;

...

//message has successfully been receivedASCIIEncoding encoder = new ASCIIEncoding();string message = encoder.GetString(message, 0, bytesRead);if(this.MessageReceived != null) this.MessageReceived(message);



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Since the events are fired on the server thread, you can't update the form directly - because you can'tmodify UI elements on threads that didn't create them. You'll have to use Invoke, which executes codeon the UI element's thread. For some more information on invoking, I would recommend this article.

I hope this helps.

Pc_Madness 6 years agowoot, thanks Reddest. :)

Anonymous 3 years agothnx Sir. I like it

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Chris Surfleet posted 6 years agoOK, I think I must be missing something here. I keep getting an error stating "You must call the start methodbefore calling this method" on the TcpClient client = this.tcpListener.AcceptTcpClient() line.

I've definately started the server, any ideas what this could be?

Thanks a lot!

Brandon Cannaday 6 years agoThat error is a result of not calling tcpListener.Start() before the call to AcceptTcpClient(). If you'resaying you definitely called it, then I don't have any other ideas. I'd double to check to make sure youabsolutely called tcpListener.Start().

Chris Surfleet 6 years agoHmm got a little further. The problem is to do with closing the server down. I can send data to itwithout error the first time, (creating the server object and sending the data from the same test casemethod) but next time I run the code I get a "Only one usage of each socket address (protocol/networkaddress/port) is normally permitted" exception. I added a method to my server called Close that simplycalls Abort on the listen thread and Stop on the TcpListener. If I call this after closing my requeststream I get an IO exception while writing to the stream, above the point where I call the closemethod??

Really confused haha

Brandon Cannaday 6 years agoCalling Abort is never a good way to close your threads - and it's not actually a guarantee that thethread will terminate. Calling Stop() on your TCPListener should unblock your listen thread and throwan exception - which you should catch and return out of your function (which will end the thread).

Your first error is caused by calling Start() while another application is listening on that port. Typically,

Server server = new Server();server.MessageReceived += new MessageReceivedHandler( Message_Received);

void Message_Received(string message){ //update the display using invoke}



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http://msdn2.microsoft.com/en-us/library/system.net.sockets.tcplistener.start(VS.80).aspx

















you can't have two TCP servers listening on the same port. Either your TcpListener was still runningwhen you launched the application again, or you have another piece of software on your computerusing that port.

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JS posted 6 years agoExcellent tutorial! Thanks a lot!

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Vishav Bandhu Sood posted 6 years agowhen i got connected to the various clients in tcp listner(server)suppose initially if there are 1000 clientsconnected but after some time it shows only 500 or 400 clients connected.actually clients are connected butserver is not responding prooerly,but after stopping server it agains shows the actual no of the clientsconnected.(i thinks this problem is related to server port buffer size)plz help .....

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Simnesh posted 6 years agoHi,

i want to send data from a client to another client through server...

please help me

Brandon Cannaday 6 years agoHow to do this depends a lot on the application you're trying to make, your protocol, and your serverarchitecture. Here's an example scenario that might get you started.

When a new client is connected, you could assign them a unique id, or they could actually send youthe id (a username or email address). This id would then be sent from another client in a request toforward the information.

This would mean your protocol would have to include the id of the client the other client wants to senddata to. On the server, you'd simply read the message, get the id of the client to forward the messageto, iterate through your clients to find the recipient, then send the data.

Simnesh 6 years agoHi Is it possible to send a class object from a TcpClient to TcpListener... I want to send an object of aclass or an array of string to the TcpListener

Brandon Cannaday 6 years agoIt sounds like remoting is what you might want here, but it can also be done using TCPClient andTCPServer.

The send an object, you'll first need to serialize it to a byte array. Then, on the receiving end,deserialize the object back into the desired object. Here's a tutorial I found on the web explaining howto do this: Object Serialization and Deserialization in C#.

Nigel Bogle posted 6 years agoI have an application which is essentially a TCP/IP Server to which up to 16 clients can connect at any one

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http://www.google.com/search?hl=en&q=C%23+remoting&btnG=Search

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time each on it's own unique port, i.e. 4001 - 4016.

The connections establish ok but after a period of time the connections seem to disconnect and I'm not surewhy. when you run NETSTAT from the DOS Prompt it shows the connections in a CLOSE_WAIT state.

The clients then have to reconnect... and so the loop goes on...

Whe I try to write back to the client and it is disconnected I get an error code of 10053 which means that thesoftware in the host machine has disconnected or something along those lines.

Has anyone else had experience of this? Could it be a timeout? How can I ensure that once my serveraccepts a client connection that it helps to maintain the established connection?

Any and all help appreciated.

Nigel.

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Dvaz posted 6 years agoThanks for the nice tutorial, just found it today.

Is there a way to start the server in its our thread at start? The reason i ask is because the user on my UIneeds to click a button to start listening, but by doing so, it blocks my main UI.

Thanks!

Brandon Cannaday 6 years agoThe server in this tutorial is created in its own thread. The constructor of the Server class creates thethread and begins the listening process. All you'd have to do is not call this.listenThread.Start() untilthe user clicks the button.

Dvaz 6 years agoAhh, i see. I used a background worker to call the listen call and it also worked, will try the other.

One more thing, i am trying to pass a connected / disconnected status to the mainform as wel as thenumber for files received, any easy way to do that? So far im using you event example to send themessage back but what are the procedures if i want to send more data back to my MainForm?

-Thanks!

Tagnard posted 5 years agoHi. i am trying to get the client to read what the server sends but i am new to this. Can you tell me what i amdoing wrong?

http://tagnard.net/2008/06/09/c-serverclient/

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Eric posted 5 years agoThanks for the nice tutorial. I tried it (ported to C++) and it works fine. Still, when exiting the main application Ican't find a way to stop a clientThread when there is an active connection. I mean I can usetcpListener.Stop(), what causes a SocketException that unblocks AcceptTcpClient()in the ListenForClientsthread, then I use break to exit the loop and this thread. But if a client is actually connected, correspondingHandleClientComm thread remains stuck waiting for something to be read. So far, I haven't found any cleanway to gracefully close the socket and to exit this thread.

I don't see how to close the NetworkStreams (as proposed in an earlier comment.) from the outside of the

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client thread. And from the inside, well the read is blocking, so...

Any idea?... Thanks, Eric

Brandon Cannaday 5 years agoI usually create an object for clients. The thread would be located inside the client object. The serverwould just keep a list of clients and whenever you stop the server, you'd loop through each client andcall a stop function on them, which calls Close on their NetworkStreams.

You can modify the above code to do something similar by keeping a List of just the NetworkStreams.Whenever a new client is connected, add the NetworkStream from HandleClientComm. Whenever aclient is disconnected, remove the NetworkStream from the list.

Eric 5 years agothanks for the suggestion, it made it.

Johan posted 5 years agoHi, have a strange problem... the tcp server connects fine with clients on the local network but 'kind of'connect with client comming from the Internet... it always wait about 16 - 20 seconds to connect, but then theremote client seems not to realize this... (also tcp port monitors show the incomming connection connectingalmost immediately, but somehow not telling the server) please help...

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Nicholas posted 5 years agoHi, i have an error message "A blocking operation was interrupted by a call to WSACancelBlockingCall" whenset tcplistner.stop(), how to solve it ?

thank you

Eric 5 years agothis is normal behavior when interrupting a blocking socket (i.e. waiting for clients).WSACancelBlockingCall is called and a SocketException is thrown (see my post above). Just catchthis exception and use it to exit the thread ('break' in the infinite while loop).

Vitalij posted 5 years agoHi! If it's possible, send me an initial code of this program. Please!

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Jason posted 5 years agoNice.. Easy to use and build on..

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Saga posted 5 years agoHi, Since i m very beginner in C# coding for TCP/IP server.. I can get the concept and working of the codethrough ur explanation and questions but i cant do it practically./. Can u please explain that with a visualmode or the screen shots of wat to do?

Please help me bro.. I m in need of it.. I will b very grateful for the help ...

Saga 5 years ago



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ya its me again Saga.. Can u please mail me the one wich i asked in the previous thread... My mail id:[email protected]

Opariti posted 5 years agoThis is a great article; who explains clearly is really someone who really knows! I didn't give it a try yet butfrom the beginning it points to the TCPListener application blocking issue. I'll bring it into a chat-typeapplication (client-server however) between two programs running on the same machine or remotely (firstboth on 'localhost'). I understand that threading the server separates it from the main program thread andavoid blocking all while in the listen loop. After acknowledging all that, just a stupid question (sorry I'm new toprogramming...): would it be possible that I make ListenForClients a method (rather than a class) of my mainthread (since I want to quickly send and read messages from/into the main thread through your TCP server)?Many thanks!

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Bryan posted 5 years agoHey, not much to add. Just wanted to say great thread. EXCATLY what i've been looking for.

THANKS!!!

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Serhat posted 5 years agoThanks

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Shinoj K posted 5 years agoHi,

i am in a big trouble to fix this problem.... can any one suggest me a control, which can display animated gifimages and text....

this is for a chat application....

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Kristian posted 5 years agoOk... so I got the client-server part done quite easily...

What I want to do now is to have two way async communication using this only connection. Is that possible ordo I have to have two connections, one for reading and one for writing, on different ports? Any other way youcan suggest?

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Joap posted 5 years agoI have a very weird problem here. When I copy and paste the client into visual C# studio 2008, it doestrecognise the .Connect method of a TcpClient.

Please help me! Thanks.

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Shinoj K posted 5 years agoHi, I have develeped webcam view in my chat.In that only one client can view webcam at time.I want to doview more than one client at time(web cam sharing).I am using TcpListner and TcpClient.Can Anyone HelpPlz.Urgent.Thanks In Advance.

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Sami posted 5 years agothank you

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Jeff posted 5 years agoGonna try yours. Too soon to tell, but no crashes so far (like mine).

One issue I have always had with the GPS via GPRS devices we track: they will un-gracefully disconnectwhen they switch cell towers, then reconnect. So eventually, there's lots of dead connections that are notrecylced. I tried making a collection and saving each client object as it's created. The idea was to purge theclients, but I am not sure how:

...so now I have the client objects in my collection. But I get errors when I try to delete them like this:

So I guess I am still looking for a way to recycle these old connections. Suggestions appreciated.

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Ken posted 5 years agoI would like to say thanks. The main article is detailed and straight forward but the additional information inthe comments has also been very helpful.

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Kemp posted 5 years agovery simple as well useful beginner like me,,,,,,,.

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Martin posted 5 years agoAnybody,

have you had any issues with a (C#) socket exiting into a CLOSE_WAIT therefore not allowing to use the

TcpClient client = this.tcpListener.AcceptTcpClient();clientArrayList.Add(client);

foreach (TcpClient c in clientArrayList){ c.Client.Close();}


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same address/port.? I am closing the connection at both ends and still get the CLOSE_WAIT (not all thetime).

I used extensively C/C++ berkley socket and I never got the problem.

Anybody?

Anonymous 4 years agoa CLOSE_WAIT usually indicates a problem in the app (server), probably from not closing the socket.You need to catch when the client closes (or times out/drops off/whatever) and close on the serverside. You should see TIME_WAIT (ok), but CLOSE_WAIT is usually not good sign.

Anonymous posted 5 years agoGood article, hope you will keep up ,creating more of it, in the same simplify style, someday. :)

Thx!

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Guilherme posted 5 years agoGood article!!! Procurei por um assim a temposs.. muito bom msm ... parabéns!!

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Ron posted 5 years agoExcellent tutorial and very useful from both clarification and simplification perspectives.

Just one thing: shouldn't clientStream.Close() be called prior to tcpClient.Close() in HandleClientComm?Otherwise, won't the network stream remain open (unless if that was by design/intention, although I don't seewhy, and how, one could recover the same stream for future use after closing the TcpClient)?

Thanks again and great work!

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Leslie posted 5 years agoAwesome tutorial. Thanks Reddest.

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Robert posted 5 years agoI am new in this tcp programing and just have question:

I have created the TCPServer.dll and tcpClient.exe, how to test thme?

Robert 5 years agoSorry give the confuse, and question is simple: How to start TCPServer?

Brandon Cannaday 5 years agoIn my example code the server is started automatically upon construction.

Johnny posted 5 years agoHi there Reddest, I am developing a MUD (multi user domain) in C# and i wanted to ask a question:

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What i need is an application just like this, but i want the ability to have events driven by commands textedinto the MUD, i’m sure you may be familiar with old school MUDs, if not its a text based D + D typeadventure game, supporting multiple users that can interact. There will be chatting of course, but mainly eachuser will have commands and need series of data stored (in class objects i’m certain)

ANYWAY, What i need is to know if this threading business will affect each user? Like if i’m player Johnnyand johnny does this or that in the game, how will other players in the room be made aware? IS this thewrong type of server for my needs? Thanks!

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Christiaan posted 5 years agoExactly what I was looking for \^\^

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Jester posted 5 years agoForgive me if this has already been answered, but I didn’t see it.

Is there a way to send the chat messages the server receives to all the connected clients?

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Razvan posted 5 years agoGreat code…simple and stable;

If you want to test your tcp server with simulated clients, you can use ‘telnet’ to achieve this.

Open a command prompt window in XP or Vista.

Type the following command:

telnet host port

where host=local computer name, ip address(127.0.0.1 will always be your own computer) or domain namethat identifies the computer on the internet. port = port number the TCP server is supposed to listen to

If you have a successfull connection then a black screen with a blinking cursor should appear. If you openmore command windows and issue the same command you will simulate multiple clients connected to theserver. Closing that command windows should disconnect that client.

Cheers,

Razvan 5 years agoForgot to mention:

sending information to your server using telnet and beeing able to parse it is not possible unless yourTCP server uses VT100 Application layer protocol, which an end programmer has to manuallyimplement it.Though i strongly discourage to do that.

You can use telnet to test server shutdown, while clients are connected and beeing able to easilytroubleshoot exceptions, manage server resources when clients connect/disconnect and eventroubleshoot timeout disconnect methods if you clients are connected, but donn’t send anything over aperiod of time.This is very a server memory friendly approach since a real server needs to handlethousands of simultaneous connections at a given time.

Anonymous posted 5 years ago

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I can get the server to send information to the client, but its a blocking call. How do you make the client listenfor incoming data from the server and keep the GUI alive at the same time?

Thanks in advance.

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Emil Haukeland posted 5 years agoYour tutorial was a great way to get starting on networking in C#. You are very good at explaining this howsog whys :)

Thanks a bunch!

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Wildhorn posted 5 years agoMan I registed JUST to tell you how amazing this tutorial is and how good you are at explaining stuff. Ibrowsed I dont know how many tutorial about this without understand shit, but with you it was so simple, easyand amazing...

/bow

You are my new god! :)

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Brad Modenfield posted 5 years agoHi thanks for good tutorials. I have a serious problem. I want to develope an "server" that can recievestreaming data from sensors (the number of could be variated), Then the data should be pushed after it hasbeen "modified" a bit, into the database (SQL Server).

I dont know where to start, im aware that it may will need some kind of a server and it looks like that i alsoneed threads and async communication.

But how can i recieve stream data directly with TCP?

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hariom posted 5 years agohi thanks for gud concepts.. but iam confused at Async ..

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Michael posted 5 years agoWorked the first time I used it. Many thanks, you saved my bacon...

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mahmoud posted 5 years agogreate explanation

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mahmoud posted 5 years agobut i think we will find "out of memory Exception" when alot of clients conected as we creare aseparate threadfor Each client so these no of threads will lead to that exception

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littleman posted 5 years agoHi thanks, for the great tutorial,

BUT the NetworkStream.Read() command seems to work only the first time. I copied your code exactly (!),compiled and started the server. When I connect via telnet 127.0.0.1 3000 (or any other client) I can justsend the first time. The second time NetworkStream.Read throws following Exeption.Message: "Theargument is out of range of valid values! Parameter: size ...

Do you have any suggestions?

Cheers, littleman

littleman 5 years agosolved .... :)

Brandon Cannaday 5 years agoWhat was the issue?

Anon999 3 years agoYes, please do tell us the solution, I am experiencing the exact same thing...

Muhammad Arshad posted 5 years agoHi, Every one i have a card reader secrutiy device of pegasus brand, which is connected on port 4001 , iwant to read and wirite data on this device any one help me please, while i am using Visual studio 2008 C#code

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Ohad posted 5 years agoHi Reddest, great tutorial and code!

I was wondering what a realistic number of concurrently connected clients (=\~ threads in this case) would bein this implementation, on a standard modern PC using winXP SP3 and VS 2008 / .NET 3.5 SP1

I realize this may depend on many factors, but a rough estimate would be great - dozens of clients?hundreds? thousands?

Much appreciated, Ohad

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Jon Hunter posted 4 years agoGreat article. Well written and easy to understand. I wish all articles were like this one !

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Anonymous posted 4 years ago


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Great article. One question though. Since the AcceptConection is blocking on the thread, How can Igracefully end everything when the Server, in my case a form, closes?

Brandon Cannaday 4 years agoWhen TCPListener.Stop() is called, it will unblock with an exception. Simply catch the exception andbreak out of the loop.

Anonymous 4 years agothat is what I was doing, just wanted to see if there was some other way that did not raise anexception.

Brandon Cannaday 4 years agoYou can probably get around it using BeginAcceptTcpClient and EndAcceptTcpClient.

tohox posted 4 years agoHi,

I've implemented your server solution and it works fine except that threads seem to be accumulating and notbeing released as the clients close their connection. Everytime a connection is caught by the TcpListener thesize of the application in memory grows by a few kB but upon the final tcpClient.Close() in theHandleClientComm the ressources don't seem to released. So my application is constantly inflating... It wasmy understanding that once the connection was closed the thread would simply vanish?

thanks!

Anonymous 4 years agoHi again its tohox,

So I did my homework thoroughly debugging my app, reading many things about threading and .Netmemory management and it appears that this memory inflation is somewhat normal given the waymanaged code works and how the garbage collector handles ressources.

When hitting the server with many requests per second the memory usage quickly grows to a few MBsmore than when the server was first started and it then tends to stabilize. After that it will occasionnalygrow or shrink but stays roughly the same. Forcing the garbage collector to do its job will momentarilyfree up a few kilobytes but memory usage will eventually crawl back up...

So, false alarm and many thanks for a great tutorial!

Anonymous posted 4 years agoThank you for the article. This is the first piece i've seen on tcp communication in c# .net. I have a questionfor you though. Is it common practice to use a blocking loop to wait for client connections? It seems a bit likea duct tape solution to me. Are there no .Listen() methods or anything of that nature? Would a .Listen()method simply wrap a blocking loop? Just seems... i don't know... inelegant? Thank you again though. Greatarticle. :)

Brandon Cannaday 4 years agoI like to use the blocking call myself, but there are asynchronous methods that won't require it. Checkout BeginAcceptTcpClient and EndAcceptTcpClient.

Rehab posted 4 years agothanks for this good article so much really i have searched a lot but this was the best i have a silly questionas i am new to network programing what happen if the accept client has no object to return??




http://msdn.microsoft.com/en-us/library/system.net.sockets.tcplistener.beginaccepttcpclient.aspx

http://msdn.microsoft.com/en-us/library/system.net.sockets.tcplistener.endaccepttcpclient.aspx

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http://msdn.microsoft.com/en-us/library/system.net.sockets.tcplistener.beginaccepttcpclient.aspx

http://msdn.microsoft.com/en-us/library/system.net.sockets.tcplistener.endaccepttcpclient.aspx

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Anonymous 4 years agorun your program and place breakpoints at the accept client line and one at the line just after that, youwill see that the accept client will not move to the next code line untill a client is connected so theobject will not be nothing

Anonymous posted 4 years agoGreat article, but how can I use this one when I want to connect to a remote computer on Internet with arouter(a local ip adress)

Brandon Cannaday 4 years agoIn this example, the TCP server is listening on port 3000. The router would have to be configured toforward that port to your desired computer.

suchislife801 posted 4 years agoWhat a clean and great sample you've posted. I was just wondering one thing. Would you be so kind toperhaps post the following code updates if its not to complicated:

Everytime the server accepts a client, this client is added to a list.

Everytime a message is sent to the server, a true or false flag is sent as well telling the server tobroadcast the message back to the client who sent it or to all clients on the list of connected clients.

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Anonymous posted 4 years agoGreat article, thanks for posting this. I have a problem though...

It seems that the server can only be connected to using a client on the same computer as the server or onthe same network (intranet).

How do I open the server up to connections from the open internet?

Thanks in advance to anyone who can help me with this issue!

Anonymous 4 years agoHere is my code:

private void ListenForClients(){ this.tcpListener.Start();


//create a thread to handle communication //with connected client Thread clientThread = new Thread(new ParameterizedThreadStart(HandleClientComm)); clientThread.Start(client); }}

using System;

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Anonymous 4 years agoFollow-up:

I resolved the issue. Apparently the corporate domain my computer was joined to had settings whichblocked all ports for incoming requests not on the domain.

ash1988 posted 4 years agoHi I've been trying to piece together some code from this tutorial for my application and have come across afew problems.

Can anyone help me out with seeing why I can't send more than one message in either direction with thecode I have, and why this would be the case. I get the feeling I've done something seriously wrong!

Thanks for any help.

Server Side

using System.Collections.Generic;using System.Linq;using System.Text;using System.Net.Sockets;using System.Threading;using System.Net;

namespace SimpleConsoleServer{ class Program { // Global methods private static TcpListener tcpListener; private static Thread listenThread; private string endl = "\r\n";

/// <summary> /// Main server method /// </summary> static void Main(string[] args) { tcpListener = new TcpListener(IPAddress.Any, 80); listenThread = new Thread(new ThreadStart(ListenForClients)); listenThread.Start(); }

/// <summary> /// Listens for client connections /// </summary> private static void ListenForClients() { tcpListener.Start();

using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;


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Brandon Cannaday 4 years agoMy only guess is that clientStream.DataAvailable is returning false. DataAvailable only returns true ifdata is available to be read. Since you're reading all of the data from the stream in the loop, it will mostlikely revert to false by the time the loop ends.

ash1988 posted 4 years agook so with that aside, am I right in my understanding that once a "clienstream" has been established betweenserver-client that they can send/receieve using this without any issues with blocking sockets or anything likethat?

In your example you have this code to send from server-client

NetworkStream clientStream = tcpClient.GetStream(); ASCIIEncoding encoder = new ASCIIEncoding(); byte[]buffer = encoder.GetBytes("Hello Client!");

clientStream.Write(buffer, 0 , buffer.Length); clientStream.Flush();

Was I correct in adding a handlecomm method at the client end because how else would the application knowhow to handle the receival of data?

Im confused in regards to the part where say I go to send a message from client-server, how is it that onlythe server "handlecomm" and not the client "handlecomm" won't see data in the stream to be read?

Thanks

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using System.Text;using System.Windows.Forms;

using System.Linq;using System.Net.Sockets;using System.Threading;using System.Net;

namespace TcpTrainServer{ public partial class Form1 : Form { private static TcpListener tcpListener; private static Thread listenThread; static NetworkStream clientStream; static string textFromClient = ""; //private string endl = "\r\n";

public delegate void MessageReceivedHandler(string message); public event MessageReceivedHandler MessageReceived;

public Form1() { InitializeComponent(); initiateListen(); }

private void initiateListen()









ash1988 posted 4 years agodisregard my last message, I got it working, you were right about the DataAvailable returning false. I've justplaced an infinte true loop around the other loop, not sure if thats the best way to get around it but itsworking!! Thanks heaps

Brandon Cannaday 4 years agoYou could just replace the inner loop with a while(true) loop. On error conditions you call break, whichwill correctly exit the loop. If you surround the inner loop with another one, you might have problemsgetting that thread (and your application) to exit.

Teres posted 4 years agoI have modified a bit client and server, so that server replies to client and they communicate until client types"exit".

CLIENT

SERVER:

Console.WriteLine("Type 'exit' to exit"); while (true) { Console.ForegroundColor = ConsoleColor.Green; Console.Write("SEND: "); buffer = encoder.GetBytes(Console.ReadLine()); if (encoder.GetString(buffer) == "exit") { break; } Console.ForegroundColor = ConsoleColor.Green; Console.WriteLine("SENDING: " + encoder.GetString(buffer)); clientStream.Write(buffer, 0, buffer.Length); Console.ForegroundColor = ConsoleColor.Red; clientStream.Read(buffer, 0, buffer.Length); Console.WriteLine("REPLY: " + encoder.GetString(buffer)); }


try { //blocks until a client sends a message bytesRead = clientStream.Read(message, 0, 4096); } catch { //a socket error has occured break; } if (bytesRead == 0) { //the client has disconnected from the server break;



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Can you tell me why only the last "method" in server works ? If I try to do the same thing with two previous"methods", after receiving first message from client and sending it back, server shows that client hasdisconnected.

On the other hand those two "methods" work fine if I don't try to do anything with buffer (just send it back).

Teres 4 years agoWhy can't I use the same buffer I received message to ?

Teddy posted 4 years agoI need help urgently.

An application written in C++ writes messages in the form of (char*) struct continuously.

I need to create a windows server ( written in c#) that would receive that message from that socket and parsethat and send the information back again in the same socket.

Please help me 1. how the c++ message will be read by c# codes? 2. How the threading model would be forthe c# application? 3.How it will write data into socket that would be readable by c++ application?

PLeeeeeASE HELP.

Anonymous 4 years agoC# will have no problem receiving CPP char*s (they point to char[]) and CPP will have no problemreceiving C# char[]s, it depends on your methods for retrieving data.

Perhaps something more "beginnerish" would be beneficial before tackling threading and sockets..

the person with the toothpaste tube posted 4 years agoexcellent tutorial

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the person with the toothpaste tube posted 4 years ago

Shankar S 4 years agois there any way to test the connectivity(telnet or ping) using C# .net if we enter the source(usually not

} //message has successfully been received Console.WriteLine("RECEIVED: " + encoder.GetString(message, 0, bytesRead));

//REPLY

/*sMessage = encoder.GetString(message, 0, bytesRead); sMessage = sMessage.ToUpper(); Console.WriteLine("REPLY: " + sMessage); message = encoder.GetBytes(sMessage); Console.WriteLine("REPLY: " + encoder.GetString(message, 0, bytesRead)); clientStream.Write(message, 0, bytesRead);*/

/*message = encoder.GetBytes(encoder.GetString(message,0,bytesRead).ToUpper()); Console WriteLine("REPLY: " + encoder GetString(message 0 bytesRead));

Console.WriteLine("Thank you for the tutorial.");


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the machine logged in) ip port and destination ip port in a simple form?

Thanks in Advance.

Anonymous one year agoAgreed

sonea posted 4 years agoHello. Need your help! In the article you've said that you usually save collection of TCPClient. Is there anyway to detect the client is discinnecting? Thanks for any advices!

Brandon Cannaday 4 years agoYes, clientStream.Read(message, 0, 4096), will throw an exception (probably IOException), whichindicates the underlying socket has been closed.

sonea 4 years agoThanks a lot! I'll try this.

Annonimous posted 4 years agoHello,

how do you stop the server? I mean, your Read call has Infinite timeout so the call will block forever.

Then, how do you can stop the server if you need to?

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Anonymous posted 4 years agoThis stuff looks interesting although I can't seem to get any of the examples to compile in Visual Studio 2005.

Can anyone post a complete compileable example of the client and server app where data communicatedbetween the client and server is displayed in a form control?

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kami posted 4 years agoHello everyone, I am new in Socket programming, I want to send file in chunks from server to client side. Asserver send packet(packetID + SizeofPacket + Data) to client side, Client save the data in buffer and sendthe response(packetID) back to server. then server looks the packetID and send the datachunk related topacketid. Can I achieve this by using TCP sockets. Can someone explain me how. Thanks

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webmartians posted 4 years agoCuriosity: the example starts a thread to handle the communications and provide the "intelligence"(HandleClientComm).

What about using

(which blocks until a connection is available) - acquiring the entire message - and then spawning a thread toprovide the process? Yes, the acquisition of the message is then in-line, but, if I read my TCP specs

AcceptTcpClient

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correctly, it will always be in-line because of the buffers.

For example:

...

...

...

Just to add to the confusion, the send is therefore stateless:

webmartians 4 years agoNever mind... Don't do it (spawn the thread AFTER acquiring the text)... The newer Windows TCP

using System;using System.Diagnostics;using System.Net;using System.Net.Sockets;using System.Text;using System.Threading;

TcpListener lr /*Listener*/ = new TcpListener(IPAddress.Parse(InternetProtocolAddress), InternetProtocolPort);for (lr.Start(); MyListenerIsNotShutDown);){ TcpClient cl /*Client*/ = lr.AcceptTcpClient(); byte[] bf /*Buffer*/ = new byte[8192]; string mg /*Message*/ = string.Empty; NetworkStream sm /*Stream*/ = cl.GetStream(); for (int ct = sm.Read(bf, 0, bf.Length - 1); 0 < ct; ct = sm.Read(bf, 0, bf.Length - 1)) mg += Encoding.ASCII.GetString(bf, 0, ct); mg = mg.Trim(); try { // Start a new thread to process this message. Thread thd /*Thread*/ = new Thread(new ParameterizedThreadStart(MyMessageProcessor)); thd.Start(mg); }#pragma warning disable 168 catch (OutOfMemoryException ex /*Exception*/) { // There is not enough memory to start the thread: do it in-line, thereby, throttling responses. MyMessageProcessor(mg); }#pragma warning restore 168

public static void MyMessageProcessor(object prmMsg)

TcpClient cl /*Client*/ = new TcpClient();cl.Connect(new IPEndPoint(IPAddress.Parse(prmAdr), prmPrt));ASCIIEncoding ec /*Text Encoder*/= new ASCIIEncoding();byte[] bf /*Buffer*/ = ec.GetBytes(prmMsg);NetworkStream sm /*Stream*/ = cl.GetStream();sm.Write(bf, 0, bf.Length);sm.Flush();






stacks do indeed provide for multiple, concurrent connections' queues being drained.

khan posted 4 years agoHello, is it possible that 2 clients connected to same server can communicate each other using c#multithreading programming?? Thanks... I need help

webmartians 4 years agoThe server merely receives and replies to clients; client to client communications are not possible ...strictly speaking.

I suppose you could write your server's message handler to recognize some kind of forwardingcommand prefix in the message (eg: "To 12.34.56.78:50000"). The sending client would have to putthat it its message. However, that brings up the question, "If the client knows the IP address and portof the other client, why is it not sending the message directly?"

khan posted 4 years agoHi, I am writing Bluetooth simulation program in c#. I am writing two clients as Master and Slave device. andone server application which act as a channel between Master and Slav device. so, Master communicate withSlave through Channel. Later I will add interference at channel application and see the effects on Master andSlave, as these Master sending a big file in chunks to Slave. Please I need your's suggestions, how I achievethis??? Thanks Khan

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mrRumble posted 4 years agohii, how to receive and send data to linux client from .NET using format

struct tcpdata { unsigned long code; unsigned char msg[256]; }

thanks,

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webmartians posted 4 years agoI got most of this working ... in a "harsh" environment (slow processors at both ends, zilch memory). Here iswhat I learned:

1- recv returns zero when its current crop of buffers for the connection are empty. THAT DOES NOT MEANTHE MESSAGE IS FULLY ACQUIRED! Maybe everybody else got this; I didn't and had to add an endian-independent, length field at the beginning of each message.

1b- mrRumble - "On the nose!" (length field at the beginning of each message) ... except that there are anumber of machines of different "endianness" that do not store the bytes of an unsigned long in the expectedorder (assuming you want to talk to not just C# nodes). You must replace that unsigned long (or long) withfour, distinct byte values, where you know that the first one is the high-order, and so on (or whatever orderyou want, as long as it's consistent).

2- When the client (sending) side is C# and the server (receiving) side is C/C++, when the C# closesocketexecutes, unread data at the server (C/C++) side (or, maybe, still in flight) is destroyed ... sometimes ... oftenenough to be catastrophic. Strangely enough, this does not seem to happen in reverse (C/C++ client sendingto a C# server). I found two WWW reports of similar behavior - "fire and forget" is not a good philosophy,here. The answer is to require some kind of acknowledgment for every transmission (for example, an emptymessage) before the sender executes closesocket.

3- The idea of the loop around the server's loop is a real frustration-preventer: having the code able to say,

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"This failure is too nasty for me to handle in the inner loop; I'll reset and restart everything!" definitely makesunit testing more pleasant. I suggest a Sleep of a good second or so at the end of the outer loop:

to give the system some cycles to tidy whatever messes it needs to clean up and, maybe, restore resourcesthat will allow the next, major cycle of your server to execute successfully.

4- Consider UDP instead of TCP. If you can do what you need to do in UDP, use it instead of TCP.Remember, UDP blasts your packets all over the place: they WILL arrive out of order. You'll need, instead ofjust a length field, a (packetN)/(ofMpackets) field in each transmission. ...but UDP is much faster, simpler,and, oddly enough, can end up being more robust than TCP. Hard to swallow, I know, but that has been ourexperience: UDP gets more data through bad pipes than TCP does.

...hope this saves somebody some grief...

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milop posted 4 years agoIf each thread is communicating through the same port, how is it that one client doesn't get the data intendedfor a different client? Does the NetworkStream object create the "isolation"?

Brandon Cannaday 4 years agoWhen a connection is made, a socket will be formed between the server and the client. Each port canhave several active sockets. The .NET framework and the OS maintain this information.

http://www.freesoft.org/CIE/Course/Section4/6.htm

http://en.wikipedia.org/wiki/Internet_socket

milop 4 years agoThanks. After a bit of a brush up on sockets I confirmed this with NETSTAT.

I have one more question, if you don't mind. In your article you stated that you like to keep the "client"object around. How would you know that a "client" object can be reused? The "Connected" property?

Thanks again.

Brandon Cannaday 4 years agoI've never reused a TcpClient object. In the example code, the client only lives in the scope of itsthread. There's no way for the server to find a client when it's needed. What I meant by "keep itaround" was to put it in some sort of collection so the server can look up a client when it needs to sendit something.

pollardomax posted 4 years agoThanks the tutorial is great, I've got it working... I would need to send data from the server to all theconnected clients.. is there any simple way to do this in your example?

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goldenfox posted 4 years ago@The Reddest: Can you give me an idea on how to use this method to allow the server to senddata(possible huge data) to coming from mysql to the clients connected to it? I would like to use thistechnique to create something like a middleware between clients and mysql server.

if (this is not a shutdown) Sleep(1000);

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Thanks,

goldenfox

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AliBaba posted 4 years agoWhen My code is in clientStream.Read(...) loop and how can I break it? Can I set a ReadTimeout such asSerialPort.ReadTimeout?

Thanks

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topagent006 posted 4 years agowhat is the maximum connection can I have using this chat method? Is it limited by the OS in term of threadsit can have? What could be other limitations?

Thanks

Brandon Cannaday 4 years agoThere's basically no limit outside of your computer's resources. Memory, threads, and availablehandles. A normal desktop should be able to handle a least a thousand.

topagent006 4 years agoWow. Thank you for your prompt reply.

ravik posted 4 years agoHi , Thanks for posting the tutorial. I need some information for sending and receiving messages throughtelnet using tcp connection after the connection and the valiadation of the login string.and the data will bestoring in the log file and the listbox in mainform. can anybody help me how can i solve this issue.

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samad posted 4 years agoHi,

you put great stuff on this page... as i can see in above example using TCP .. Does TCP client create oneseperate thread on TCP listener server and thumb of rule there shouldnt be processor*2>running thread onserver side..

i saw some articles where they explain select and pooling technique for nonblocking server...and they usedsocket class rather thn TCP

i am trying to implement one server which can serve thousands of clients ... do you have any good exampleor article regarding that

Thanks in Advance

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lou posted 4 years agoHi,thanx for your good tutorial.

here is question as Nigel asked it long ago. i have the same problem.and i could not fine the answer,can any

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body help me.

I have an application which is essentially a TCP/IP Server to which up to 16 clients can connect at any onetime each on it's own unique port, i.e. 4001 - 4016.

The connections establish ok but after a period of time the connections seem to disconnect and I'm not surewhy. when you run NETSTAT from the DOS Prompt it shows the connections in a CLOSE_WAIT state.

The clients then have to reconnect... and so the loop goes on...

Whe I try to write back to the client and it is disconnected I get an error code of 10053 which means that thesoftware in the host machine has disconnected or something along those lines.

Has anyone else had experience of this? Could it be a timeout? How can I ensure that once my serveraccepts a client connection that it helps to maintain the established connection?

Any and all help appreciated.

Nigel.

Brandon Cannaday 4 years agoI don't know what could be causing it, and it's something I've not experienced. I checked thedocumentation for TcpListener and TcpClient, and their timeouts are all initialized to infinite.

Bubba posted 4 years agoThis is a really great example and I have a working implementation. Thanks. One thing I can't seem to wrapmy head around though.

In the scenario you have covered, a client sends a message to the server and the server responds. How doyou set up for a scenario where the server can also send a notification to the client. The client would alwayshave to be in a listening state (ie: bytesRead = clientStream.Read(message, 0, 4096); ) which would causeissues when the client sends a command and is waiting for a response from the server.

Would I need two connections to handle this or is there a more elegant way to accomplish this ?

Brandon Cannaday 4 years agoIf the client sends a request and is waiting on a response, there's no guarantee that the notificationwon't be received before the response.

This scenario should be handled in whatever protocol you've designed for communication. Typicallypeople reserve the first few bytes for the type of message being transferred. So if the client is waitingfor a response of type n, and receives a different message type, it can process the notification andcontinue waiting for the message.

lou posted 4 years agoThank you very much.

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lou posted 4 years agovoid main (Hi...arg,events,help) { i want to save tcpclient in a collection i used Hashtable and then use anarray of TcpClient but when server want to send data t specific client with specific ConnectID it say that cannot use dispose object it means that the tcpclient that i saved in server isdisconnected.client.(connected==false) i think my previouse problem has the same source as this is. so if imam wrong in saving client how should i do that.and be able to send info from server to specific client. [editpost] after i post this i found that the thread that this client has run on it(also other client on their own thread)is stoped.and i think this is the source of error 10053 software in you host disconnect you.(sth like that).but i


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dont know why the threds stop afterward.and i also geuss it might be time out problem as you sais it is finitebut as i trace and load connection from collectio at first it is connect but after seconds as i stay in Isend() itwill disconnect and my stream writer can not write to dispose object so if the problem is from timeout howshould i do that. so any buddy has any idea, thanx 4 ur help;

and here is the code.

} here is my server class and send function

and here is COnnection stat class that hols my client information to reconnect to them i

class Server : packetizer { #region Variable Scope private Socket socket; private TcpListener tcpListener; private Thread listenThread; private Queue thread_Queue;//it keep thread id inorder to dispose after disconnection private delegate void setText(string str); private TextBox Logger; private static int ConnectID; private Connection_State CS; #endregion

public Server(TextBox logger,Connection_State cs) //Constructor { Logger = logger; CS = cs; }

public void start_Server() //Point to start Server { this.tcpListener = new TcpListener(IPAddress.Any, 1313); this.listenThread = new Thread(new ThreadStart(ListenForClients)); this.listenThread.Start(); }

private void ListenForClients() { this.tcpListener.Start(); Invoking_Logger("Server startlistenning..."); thread_Queue = new Queue(); TcpClient client = null; while (true) {

public struct CData { public Socket structSocket; public TcpClient structTcpClient; public Thread structThread; }

class Connection_State {



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Perry posted 4 years agoDon't know if I'm asking the same as the guy above me, but I'm asking it more simple anyway. How do Isend to all connected clients? I've tried adding all tcpClients to a list and I tried to send to their streams, butunfortunatly I don't recieve a thing in my client, while I can send data back to a single client uponconnection...

Here's the 'sending' code:

#region Variable Scope private Hashtable Accepted_Client = new Hashtable(); public CData ClientHolder = new CData(); #endregion

public Connection_State() {

}

public Hashtable Acp_Client { get { return Accepted_Client; } set { Accepted_Client = value; } }

//Add new client that connect to sever to this HashTable public void Add_To_Acp_Client(int ConnectID, CData structtcpthread) { Accepted_Client.Add(ConnectID, structtcpthread); }}

public void sendToClient(String line, TcpClient client) { try { NetworkStream stream = client.GetStream(); ASCIIEncoding encoder = new ASCIIEncoding(); byte[] buffer = encoder.GetBytes(line + "\0");

stream.Write(buffer, 0, buffer.Length); stream.Flush(); } catch { connClients.Remove(client); myInterface.logTxt.Invoke(new AppendTextDelegate(writeIntoLog), ("Client Disconnected."+Environment.NewLine));

} }

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Benio posted 4 years agoHi,

I've made an application "client -> server communicator" made your way from the tutorial(btw.I LOVED IT!! Allyou need in an excellent compact form. Thank you for it!). I use it to send over a message to a PC in mycompany to start backuping itself. Everything works fine when I connect client and server to my router in theroom, but when I take the PC for backuping downstairs where it belongs the server responds somethingsimilar to "Connection cannot be made as the server actively refuses it." The machines ping fine! I work in alarge company with proxies and stuff and I assume the problem is the IT security, if so, how can I make theconnection between the 2 PCs? - I really wouldn't want to involve IT "experts" responsible for security here todo it, as it would be done after 2012, and it'd be too late because it'd be after the end of the World :)

ps. Thank you for the tutorial. If the application works maybe I'll get a raise :)

Cheers, Benio

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Feez posted 3 years agoI am in trouble. Is it possible that same client and same server creates mutiple connection. Because i need toknow the status of same client multiple request response from server. so that there won't be any businessloss.

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cdutoit posted 3 years agoHi,

I am trying to send an acknowledgement back to the client once they have sent a message to the server.

I where should I add the code below to the HandleClientComm to get it working?

HandleClientComm

public void broadcast(String line) { for (int i = 0; i < connClients.Count; i++) { sendToClient(line, connClients[i]); } myInterface.logTxt.AppendText("Message broadcasted to " + connClients.Count.ToString() + " clients." + Environment.NewLine); }}

byte[] buffer = encoder.GetBytes("Hello Client! Message Received!");clientStream.Write(buffer, 0, buffer.Length);clientStream.Flush();

private void HandleClientComm(object client){ TcpClient tcpClient = (TcpClient)client;

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The listener on the client does not pick anything up if I just add it below the

Not sure what I am missing?

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MRB posted 3 years agothank you for tutorial but in this part

it has error no connection could be made because remote machine refused it

can someone help me?

MRB 3 years agosorry, I had stupid mistake :)

anonhj one year agohello, i face the same problem as well, how you solve it? can tell me??

NetworkStream clientStream = tcpClient.GetStream();

byte[] message = new byte[4096]; int bytesRead;


try { //blocks until a client sends a message bytesRead = clientStream.Read(message, 0, 4096); } catch { //a socket error has occured break; }

if (bytesRead == 0) { //the client has disconnected from the server break; }

//message has successfully been received ASCIIEncoding encoder = new ASCIIEncoding(); System.Diagnostics.Debug.WriteLine(encoder.GetString(message, 0, bytesRead)); }

System.Diagnostics.Debug.WriteLine(encoder.GetString(message, 0, bytesRead));


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thanks..

fwsteal posted 3 years agoi read the article and seems good; have a question about getting the data back from the server. How do i dothat?

I have two code files below:

client form -- windows form with a textbx for remote ip address and port; button for connect to device; statustxtbox based on connection; message txtbx to send to remote sever; send button; message received txtbox.

client.cs

server.cs

using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Linq;using System.Text;using System.Windows.Forms;using System.Collections;using System.Threading;using System.Net;using System.Net.Sockets;using System.IO;using System.Net.NetworkInformation;

namespace TCPServerTutorial{ public partial class Client : Form { IPAddress ip; const int port = 1234; string myIP = string.Empty; string strMode = string.Empty; string strAddress = string.Empty;

TcpClient client = new TcpClient(); Server server = new Server();

public Client() { InitializeComponent(); txtbxIPAddress.Text = "192.168.10.147"; txtbxPort.Text = "1234"; }

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Windows.Forms;using System.Net.Sockets;

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Any help would be great. Thank you.

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Anon999 posted 3 years agoHi.

Thank you for an excellent example!

However, I am having a problem, I want my server to send a short string to each client as they connect to theserver, but I keep getting this error on "NetworkStream.Write":

Here is my code:

using System.Threading;using System.Net;

namespace TCPServerTutorial{ class Server { //a simple threaded server that accepts connections and read data from clients. private TcpListener tcpListener; //wrapping up the underlying socket communication private Thread listenThread; //listening for client connections const int iPort = 3000; //server port

public Server() { this.tcpListener = new TcpListener(IPAddress.Any, iPort); this.listenThread = new Thread(new ThreadStart(ListenForClients)); this.listenThread.Start(); }

private void ListenForClients() { this.tcpListener.Start(); //start tcplistener

//sit in a loop accepting connections while (true) { //block until a client has connected to the server TcpClient client this tcpListener AcceptTcpClient();

Specified argument was out of the range of valid values.Parameter name: size

class Network { private const int bufferSize = 8192;

private IPEndPoint serverEndPoint; private TcpClient tcpClient = new TcpClient(); private NetworkStream netStream; private Thread receiveThread;






I have been googling, but not been able to find anything that would explain why I keep getting that error.

Thankful for any help you can give me!

Anon999 3 years agoAhhh, too early in the morning here for me ;)

Here is my server code:

public delegate void MessageReceivedHandler(string message); public event MessageReceivedHandler MessageReceived;

public Network(string ServerAddress, int ServerPort) { try { serverEndPoint = new IPEndPoint(IPAddress.Parse(ServerAddress), ServerPort); } catch (Exception e) { MessageBox.Show(e.Message); } }

public bool ConnectToServer() { try { tcpClient.Connect(serverEndPoint); } catch (Exception e) { MessageBox.Show(e.Message); }

class Network { private const int bufferSize = 8192;

private TcpListener tcpListener; private Thread listenThread;

List<Thread> clientThreads = new List<Thread>(); List<TcpClient> clientList = new List<TcpClient>();

public delegate void ConnectionEstablishedHandler(TcpClient tcpClient); public event ConnectionEstablishedHandler ConnectionEstablished;

public void StartListening() { tcpListener = new TcpListener(IPAddress.Any, 3333); listenThread = new Thread(new ThreadStart(ListenForClients)); listenThread.Start(); }

public void StopListening(bool DisconnectAll)






Brandon Cannaday 3 years agoI noticed a potential problem in your code. You allocate buffer to the size of 8192, then immediate setthe reference equal to the output of encoder.GetBytes. Next, while reading from the client, yourattempting to read 8192 bytes into a buffer that's now much smaller.

tleylan posted 3 years agoJust a quick note to offer a solution to the blocking call to AcceptTcpClient(). The TCPListener class has aPending() method indicating whether there is a client to accept.

I added a Boolean property "listening" to control the loop (rather than using "true"). Inside the loop there is acall to Pending() and only if that returns true is there a call to AcceptTcpClient() which should not block.

When you need to stop the server set Listening to false. The loop exits and we an opportunity to calltcpListener.Stop().

Log files confirms that it is working for me...

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Anonymous posted 3 years agoI just want to share what I'm doing. I made a chat program/application(with GUI) using C#.NET and I usedyour codes as reference, it's working fine. I don't actually have an error or problem with my codes. I used theserver as bridge only and I can broadcast messages sent from one client to all clients connected. Then Imodified it, added some feature and made it work like yahoo messenger or skype but for a local areanetwork only. I have login, registration and I am now working for private messages and addingfriends(accepting or rejecting requests). Clients can only use the application if the server is executed on mycomputer because the ip I set for the clients is my ip.

Now, I have some questions. Is it possible to broadcast the server's IP so that I won't use a default/fixed ipaddress for the clients to connect? If yes, how will the clients get/search the server's ip? If I want to makeanother chat application and I want to make it that it won't matter who logs in first, will it be possible to makeevery client the server themselves? How will they connect to each other? I already had done this using VB6but with the use of winsock.

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Massi636 posted 3 years agoStop problems; this is may way after have read all posts: added [language] server.Stop()[/language] thatsimply do a [language]this.tcpListener.Stop();[/language] from the closing event of the main form. Then added[language] List clientList = new List();[/language] and added a client in my collection each time a

{ tcpListener.Stop();

if (DisconnectAll) { foreach (TcpClient tmpClient in clientList) { tmpClient.Close(); } } }

private void ListenForClients()


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[language]clientThread.start();[/language] then catch the exception in the[language] while(true)[/language] andclose all client in the list. I suggest to check with processExploer: it's working fine! Many thanks!

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Hans posted 3 years agoThis is a good article and still valid today. But you should use the ThreadPool instead of creating a newThread every time when listening. This will reduce a lot of stress when receiving messages and it will preventthe CLR from having to perform many garbage collections due to a lot of discarded threads.

Brandon Cannaday 3 years agoIn most cases you are correct. The ThreadPool does have a limited number of threads (this can bechanged). If the app is handling hundreds or thousands of clients, the ThreadPool will queue yourrequest indefinitely until a thread becomes available - which may never happen if clients aren'tdisconnecting.

ak.naser posted 3 years agoYour program is well work in local net work. but failed in internet.

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ak.naser posted 3 years agoi want a clear article for TCP server / Client run over inter net any one help me

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Anonymous posted 3 years agoThe Reddest,

How can I send some data back to a client and then read that data?

I can't seem to get the code you supplied to work. Could you provide some working example code for me tostudy please?

Thanks.

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Francisco posted 3 years agoExcellent tutorial. Do you have something similar for a threaded client?

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Mauricio Sierra posted 3 years agoGracias men! me sirvió mucho! excelente ejemplo para empezar a programar! Como puedo hacer massegura la conexión TCP para evitar hackers?

Thanks man! served me! excellent example to start programming! How I can make more secure TCPconnection to prevent hackers?

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anvas posted 3 years agoHi,

u guys amazing Advance Thanks

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Anonymous posted 3 years agoNice! And easy to package with a NotificationAreaIcon application so that everything is not just available atyour fingertips, but its activity is visible just by changing the icon! A nice little addition would be including anamed pipes server both client-side and server-sode, so that you can not just run information around frommachine to machine, but target other objects on any specifc machine that listen to the pipe server.

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Joe posted 3 years agoThe first comment was over 3 years ago and they've been ticking away ever since. It's not just that the codeis clear, it's that the explanations were written clearly too. Excellent work!

I loathe the trite "help me write tcp server program! give me code!" comments. Many questions can beanswered by reading through the comments before you post. Although, after 3 years that's getting a bit timeconsuming. :)

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Anonymous posted 3 years agoAny working examples of client reading/receiving data from server..??

I think I have the right code for the server to send data, but not sure how or what event the client uses toreceive.

Thanks

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rkrijger posted 3 years agoThank you for this great example! I found it to be very useful. A few questions will arise, though:

Why not use:

Instead of

?!?

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rkrijger posted 3 years agoNever mind... It doesn't compile with "TcpClient" instead of "object". Sorry.

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private void HandleClientComm(TcpClient client)

private void HandleClientComm(object client)


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Anonymous posted 3 years agohow I can create a tcp server in c # .Net using MFC serialization of messages

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AnonymousFF posted 3 years agohow I can create a tcp server. Net c # receive and reply to messages MFC serialization

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Agehack posted 3 years agoi'm using oscar protocol as used in icq. it's so easy to send ANy data any length with FLAP format. goodarticle. =)

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boyparka posted 3 years agoHi there,

Just a quick thanks for an excellent tutorial. It helped me out a lot.

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santhosh posted 3 years agohey first of all excellent tutorial. I am trying to create a GUI socket server.

The goal is simple.

1.Open a port 2.keep sending data to the port 3.the data is given from a textbox in the gui and must be sentafter the button is pressed. 4.Do NOT CLOSE THE CONNECTION to the port until a button is pressed in theGUI.

I have done some part of it but the problem i m facing with my code is i am not able to split the accept clientconnection part from the send data to client part.

Hence each time i click my button to send the data i have to close the connection and open a newconnection again. Please help me with this. The code below executes on button press. As you can see eachtime i have to close the socket and redo everything on each button press. I am not able to split it into parts.Please help me.

Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

IPEndPoint ip = new IPEndPoint(IPAddress.Any, 9999);

socket.Bind(ip); socket.Listen(10); Console.WriteLine("Waiting for a client...");

Socket client = socket.Accept(); IPEndPoint clientep = (IPEndPoint)client.RemoteEndPoint; cliStatusLbl.Text = "Connected with Client";

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David S posted 3 years agoI solved the same thing using the asynchronous calls built into the object. This will leverage the threadhandling built into .Net and you should have less issues with hanging threads. I tested this as part of a HTTPhandling program and it was lightening fast and definitely was using multiple connections at the same time.

string sndCmd = "|" + this.keyTxt + "|" + this.valTxt + "\n";

byte[] data = new byte[1024]; data = Encoding.ASCII.GetBytes(sndCmd);

client.Send(data, data.Length, SocketFlags.None); Thread.Sleep(2000);

client.Close(); socket.Close();

using System;using System.Net;using System.Net.Sockets;

/// <summary>/// Multithreaded routine to handle concurrent Tcp connections on a single endpoint/// </summary>public class TcpHandler{ public bool listening; public TcpListener listener;

public void Main() { Byte[] ip = {127, 0, 0, 1}; IPEndPoint endPt = new IPEndPoint(new IPAddress(ip), 3000);

this.listener = new TcpListener(endPt); this.listener.Start();

Console.WriteLine("Listening");

this.listening = true; listener.BeginAcceptTcpClient(HandleRequestAsync, null);

Console.WriteLine("Press 'Enter' to exit..."); Console.Read(); listening = false;

listener.Stop(); }

public void HandleRequestAsync(IAsyncResult ar) {

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Gulshan Garg posted 3 years agoHey Dear, Please send me a server side code to communicate with client, get data from client end and senddata to client end while a number of clients are online.

With Thanks

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mahdi87_gh posted 3 years agoHi all my friends thanks for this good article. i want to send a dataTable object through tcp/ip from client Toserver. by this article ,now i can send text from client to server, but i don't know how to send dataTable? if iconvert dataTable to byte[] and it's size become more than buffer size, my data will split into two or morepackets. how should i merge them on the server? please help. thanks

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Chris posted 3 years ago

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Barter posted 3 years agoHi,

The tutorial was great and very helpful, but I'm making a server system for some kind of group chat thing, butI have no idea how I can have the client-side application listen for messages getting recieved from the server.

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Anonymous posted 3 years agoHi,

OK I'm sure this tutorial is great but I can't get it to work. I've been searching online for 90 minutes and Ican't find a simple WORKING program that I can simply cut and paste into Visual C#2010 and get to work.

Can you please make a simple program that on button1 click runs the server code, button 2 click runs theclient code, and button3 sends text from client to server. That way one simple program does it all. I'm goingnuts that I cant find a working example that does that. (well i found one that is a console application).

Thanks.

Anonymous 3 years agobutton 1: server

private void btnServerCreate_Click(object sender, EventArgs e) { if (TCP_Server == null) { TCP_Server= new Server();

/// <summary>/// Great tutorial/// </summary>/// <returns>Extra time for a cold beer.</returns>public bigInt Thanks();

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// Ereignishandler aufrufen wenn eine Message empfangen wird TCP_Server.MessageReceived +=new Server.MessageReceivedHandler(Message_Received);

btnServerCreate.Enabled = false; } }

button 2: client

private void btnClientSend_Click(object sender, EventArgs e) { TcpClient client = new TcpClient();

//IPEndPoint serverEndPoint = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 3000); IPEndPointserverEndPoint = new IPEndPoint(IPAddress.Parse("192.168.2.105"), 3000);


NetworkStream clientStream = client.GetStream();

ASCIIEncoding encoder = new ASCIIEncoding(); byte[] buffer = encoder.GetBytes("Hello Server!\r\n");

clientStream.Write(buffer, 0, buffer.Length); clientStream.Flush(); }

Anonymous posted 3 years agoHello,

This approach creates one thread per client. I am curious if this is the way to go. I'm been trying to findarticles on recommendations to the max number of tasks.

If I had 100 users logged on at once, hence 100 threads, is this ok or will I hit performance issues.

Brandon Cannaday 3 years agoThe number of threads is unlikely to be a performance concern. It depends on what your server isdoing, but a basic chat server could probably handle thousands of clients.

Aaron posted 3 years agoI'm having a peculiar problem where clients can connect, but are sometimes automatically disconnected. Thishappens on/off with periods ranging from minutes to hours in which clients are automatically disconnectedright after they connect.

I've left the original code exactly the same, and have only added some Console.WriteLine calls to elaborate.This is what the console reads:

--- Client connected at 5-5-2011 Client disconnected ---

The connection also does NOT show up in netstat after this happens.

I'm using a flash application running from a webserver on the same device to connect to the server. The flashcode to connect looks like this:

What's mostly eating me about this, is that it appears to be completely random. I've found no consistentfailure/success, not with browser types, specific computers, IP's, OS's, etc. They all fail/succeed periodically.

Aaron 3 years agoFailed to note one thing: there is also no socket error on the server-side. It simply breaks out of the

xmlsock = new Socket();

xmlsock.addEventListener(ProgressEvent.SOCKET_DATA, serverData);xmlsock.addEventListener(Event.CLOSE, connectionLost );xmlsock.addEventListener(IOErrorEvent.IO_ERROR, ioError );xmlsock.addEventListener(SecurityErrorEvent.SECURITY_ERROR, securityError ); xmlsock.connect("SERVER_IP", 3000); //omitted the actual ip, for obvious reasons



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while loop due to bytesRead being 0.

It makes me wonder if there is anything about the actionscript side of this that might be causing suchinstability, like the Read call returning early and having read nothing.

Aaron 3 years agoAlso confirmed through a remote desktop connection to the server, that the problem only happenswhen trying to connect from outside of the server's network.

Upon logging onto the server, I opened a web browser, went to the website address that is pointing tothe webserver's IP, and attempted a login. This worked fine.

Tried the same thing from my own PC, got disconnected right away. What could be causing thesedisconnects, if not the software itself? All my firewalls are open, and I have a public IP address on theserver (which connects directly to the ISP, ergo there is no router)

Aaron 3 years agoI found a workaround for my problem.

It turns out there was something about the circumstances of the initial connection attempt that causedthe connection to destabilize. I implemented a once-a-second ping message from the client, and if itdidn't receive a pong within a few seconds it would disconnect and try to reconnect to the server.

Subsequent connections are stable for some reasons. I'm still unclear as to why the initial connectionis predominantly severed, but it could have something to do with the fact that it's done almostimmediately after the SWF starts running.

stes posted 3 years agoThanks a lot for this tutorial! In order to get started with the issue, I searched for a quick and plain tutorial.Well, let's say I was not disappointed!

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Hari posted 3 years agoHi,

How do i test this with client sending data and server returning back?

I am using Visual studio 2010 and i created a console application for server. Then , i created another consoleapplication for the client inside the same solution . And when i run the solution, nothing happens. Am imissing something ?

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eyal82 posted 3 years agoHey Brandon,

I have a problem figuring out how to send a message from client to client through the server with threads. Forexample suppose i have two clients(A and B) connected to the server, and i want to send a message fromclient A to client B.

So at this moment in the server i have two threads(T1 and T2) for the two clients and the two threads areblocking at read(). Now im doing this: 1. Client A sending a message to the server (with data and client B id).2. The server recieve the message in thread T1(client A thread). 3. The server gets client B id from themessage. 4. The server finds client B from the clients collection, and gets his NetworkStream. 5. The serversends the message using this Stream with write(). 6. The server goes back to read() in this thread(T1).


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The questions are: 1. Is it ok that all of this was made in thread T1? I mean is it ok that im also communicatewith client B through thread T1? or should i somehow tell thread T2(client B thread) to send the message toclient B? 2. Is it a problem that client B networkStream is used in thread T2(blocking with read()) and also inthread T1(with write())?

I really would appreciate if you could help, thanks! Eyal

Brandon Cannaday 3 years agoThe threads in the server should primarily be used to read from the clients. They should rarely beinterrupted for other tasks.

?1. Since communicating with client B could take up to 30 seconds (or whatever your timeout is), Iwould not recommend using T1 to send the information. You'd be blocking yourself from reading anycommunications from client A while you're attempting to transmit to B. I would recommend havinganother 'transmit' thread for each client and a queue where messages to transmit could be added. T1would receive a message, get client B's queue, add the message, and the return to reading. client B'stransmit thread would continually be pulling messages out of the queue and sending them.

?2. The NetworkStream object can be read and written simultaneously from different threads. I don'tthink multiple threads can safely write to it simultaneously, so whenever you're using it for writing, justsurround it with a lock.

eyal82 posted 3 years agothank you for the fast reply, ok so for each client i will have a "read" thread and a "transmit" thread.

?1. Do you recommend to maybe add another thread for each client that would acutualy do the work? i meanafter the "read" thread gets the message it adds it to a "jobs" queue, the "doWork" thread would continuallybe pulling messages out of this queue, do the actual work according to the protocol and prepare aresultMessage, then adds the resultMessage to the destination client "messageToTrensmite" queue that the"transmit" thread will send to the client?

?2. When you say "the transmit thread would continually be pulling messages out of the queue" you meanthat it continually keep chacking if the queue is not empty? something like:

or maybe its better if some event will trigger it to check the queue?

Brandon Cannaday 3 years ago?1. I don't think another thread would be necessary for handling the message - unless the contents ofdoWork could take a while and begin blocking the read thread. If all you're doing is parsing theprotocol and building a simple response, I think the read thread can do that.

?2. Polling the queue would be fine and probably the simplest approach (I'd stick a sleep in theresomewhere though). Here's an article talking about a blocking queue, which would essentially blockthe thread until something was enqueued - this is probably the most correct solution, but is moredifficult to implement.

Pool Eng posted one year agoHello Reddest: I come From ROC(Taiwan). This is a good example better than MSDN. It's quite simple and

while(true){ if(!queue.isEmpty) { //handel message }}




http://stackoverflow.com/questions/530211/creating-a-blocking-queuet-in-net

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clean,thanks for this Tutorial

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shafyxl posted one year agoBeginners!! better to see the MSDN example fist http://msdn.microsoft.com/en-us/library/system.net.sockets.tcplistener(v=VS.90).aspx.

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Louhike posted one year agoGreat example ! The code is well written and simple and we easily understand everything just by looking atthe code. Thanks a lot, it's really helpful.

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Mouayad AL ZEIN posted one year agoFirst of all, thanks a lot for your article, it helped me a lot in understanding the whole concept.

I have one question :

Let's suppose I want to build a Server class and a Client class using what you have written in your article, Istill can't figure out how to make a Client class so that each time I create a client object I can connect it to theServer ?

Your code shows pretty well how to define a server that listens to clients, but how do I launch the clients ?

my question might seem stupid to you, but I'm new to networking and I need an answer badly.

Best Regards

Brandon Cannaday one year agoHere's the shell of a possible client class that may help you out a little.

public class Client : IDisposable{ TcpClient _tcpClient;

// Connects the client to a server at the specified // IP address and port. public void Connect(IPAddress address, int port) { _tcpClient = new TcpClient();

IPEndPoint serverEndPoint = new IPEndPoint(address, port);

_tcpClient.Connect(serverEndPoint);

// Create a thread to read data sent from the server. ThreadPool.QueueUserWorkItem( delegate {

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rakesh posted one year agothank u so much for this post.. this really helped me a loooot......

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remlap21 posted one year agoExcellent article thank you so much!

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Anonymous posted one year agoHI first sry my english.

This is a good example but my client has had several requests.when the server responded with GetBytes()how I jump to the next client request?getstring()

Anonymous one year agoi mean this:

-client send to server -server answer and wait for next request and answer etc.

Anonymous posted one year agoI used your code and my Console just sits there and does nothing...

Anonymous one year agoNever mind

Yehonatan posted one year agoHi,im starting to learn c# again and i wanted to ask something. On the article above you gave us thedirections to create TCP server but what if i want to create TCP client? where can i learn how to create oneand not just to copy and paste code? Thanks.

BTW - your captcha is easy to break if someone using php.

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Anonymous posted one year ago

Read(); }); }

// Sends bytes to the server. public void Send(byte[] buffer) { _tcpClient.GetStream().Write( buffer, 0, buffer.Length);

_tcpClient.GetStream().Flush(); }

private void Read() {

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Iam getting following error at this.tcpListener.Start();

system.collections.listdictionaryinternal An attempt was made to access a socket in a way forbidden by itsaccess permissions..

Please can any one help..

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Anonymous posted one year agohi, im starting to learn on c# client server socket programming. sorry a dumb question.. is your code amultithreaded server socket programming? a server connect by many clients?

thank you.

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Anonymous posted one year agoSorry for being a newb but how do I treat every client if I want to send something to them?

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antonio posted one year agoHello

First of all thanks for the tutorial it was really helpful to understand tcp.

I'm working in a monitoring application based in a Modbus TCP IP communication model, the client has atimmer that sends one command to read the registers in the remote server, and the server recives thecommand and sends back the information, the fact is that I dont know if I should use synchronous orasynchronous calls.

thanks

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posted one year agoNice explanation, thanks....!!

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ch0eb1t posted one year agoallright, I found a very bad problem. when I close the program by clicking the x button on the top right cornerof the winform, after starting the thread of course. The listener is still running and you can see it with the taskmanager. if you use the build mode, the IDE won't exit from the build mode except when you stop it. or ifyou're using (ctrl+F5), do it again, and it will give you an error.

This problem's so bad. even though the thread and program is closed, the this.tcpListener.AcceptTcpClient();line is still running.

Brandon Cannaday one year agoYep, the code here is not feature complete, just a shell. When the app closes, just call Stop on theTcpListener.

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ch0eb1t one year agoI'm sorry, but can you please tell me where to put the tcplistener.stop whenever I close the program? :)the server code is written in different class from the main winform app. The server thread is createdwhen I clicked a "Start" button. I'm trying to solve this problem but I'm getting a dead end.

Brandon Cannaday one year agoThe server class should expose some way to start and stop it.

view all 4 comments

anonhj posted one year agothanks for the code

i have error in this:


i dont know how to solve it, can help me on it.

thanks again.

ch0eb1t one year agodoes the client code run on different machine?

anonhj one year agoyes, i try to run it on different machine and also run on same machine. For now, the error was solved,but, both client and server seem not connect to each other, i post my code down there, if possibleplease check for me. thanks a lot.

ch0eb1t one year agochange the 127.0.0.1 on the client program to your server PC IP address

BlueButtons posted one year agoHello, i was wondering, how do you connect to computers that have a different IP address. For instance, if iwant to run your client and server seperately on two different machines, loopback (or using the localhost)won't allow for this....

Not too familiar with networking, any help would be greatly appreciated!

public class Server{ public void Start() { // Called by the application when the // start button is pressed. }

public void Stop() { // Called by the application when it // it closed. }}




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ch0eb1t one year agoThe two computers must be on the same LAN

consider it: Computer A IP address : 192.168.0.5 running the server code Computer B IP address :192.168.0.6 running the client code

in Computer B, change:


with


anonhj posted one year agohi, i had been trying out the code, no error, but dont know why both client and server are not connect to eachother, nothing response, something wrong in my code, please help me, thanks a lot.

server code

client code

using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Linq;using System.Text;using System.Windows.Forms;using System.Net; //networkingusing System.Net.Sockets; //networkingusing System.Threading; //networkingusing System.Net.NetworkInformation; //monitor bandwidth

namespace NBCS_serverlogin{ public partial class NBCSadmin : Form { private TcpListener tcpListener; private Thread threadTcp; static NetworkStream clientStream; const int portnumber = 3333;

//public delegate void ChangedEventHandler(object sender, EventArgs e); // public event ChangedEventHandler Changed;

public NBCSadmin() { InitializeComponent(); portnotxt.Text = "3333"; // initiateListen(); }

private void initiateListen()









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umm posted one year agoAfter i have used the send method from server, how do i open that message on client?

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Mikki posted one year agoWhat do you mean by the word "block?" That it stops waiting for clients until one has connected?

Brandon Cannaday one year agoIn this case, block means execution will not continue until a client connects or an error occurs.

BAJA posted one year agosomeone can put a link whit a functioning code, because i am nuub and y dont undertant so well

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using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Linq;using System.Text;using System.Windows.Forms;using System.Net;using System.Net.Sockets;using System.Threading;using System.IO;

namespace NBCS_Client{ public partial class NBCSuser : Form { static TcpClient clientuser; IPEndPoint serverEndPoint; NetworkStream clientStream; const int portnumber = 3333; string myIPAdd = string.Empty; string strgAddress = string.Empty;

public NBCSuser() { //InitializeComponent();

InitializeComponent(); ipaddtxt.Text = "127.0.0.1"; portnotxt.Text = "3333"; }

public void initiateListenUser()

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eyal82 posted one year agoHey Brandon,

I know this is a bit out of scope but can you show how to add SSL support if its not too complicated?

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hossam posted one year ago

I got an error in the last two lines

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antonio posted one year agoHello

I'm new in C++ and I'm working on the client code but I always get the same error C3364:'System::Threading::ParameterizedThreadStart' : invalid argument for delegate constructor; delegate targetneeds to be a pointer to a member function

I also tried with ThreadPool::QueueUserWorkItem(delegate Read_Multipl_Reg(direccion, unidad,referencia,cantidad,registros));

but it doesn't work either

can someone help me to see how to solve it

thanks

NetworkStream clientStream = tcpClient.GetStream();ASCIIEncoding encoder = new ASCIIEncoding();byte[] buffer = encoder.GetBytes("Hello Client!");


#pragma once#include "stdafx.h"#include <winsock2.h>#include <stdio.h>#include <conio.h>#include <iostream>#include <fstream>#include <string>#include <ios>using std::cout;using std::cin;using namespace System;using namespace System::Text;using namespace System::Net;using namespace System::Net::Sockets;using namespace System::Threading;

public ref class cliente


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scriptinphp posted one year agoGreat Tutorial.

question though, kinda of off topic, but here goes:

I am in need of a traceroute application, and have found source for one, but I have tried changing it to useTCP (with my extremely limited knowledge). Is there any way you could help with conversion to work withTCP vs UDP?

http://dice.neko-san.net/2011/01/my-traceroute-for-windows/

you can respond to me at \^\^ gmail.com

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Anonymous posted one year agohi,

first of all, nice tutorial!

im new to client/server programming. but i was wondering if you could help me with a project im working on.

i'm trying to send a video file from client to server which is 20 megs big.

my question is, what do i need to change in the code to be able to stream video?

and how do i split the bytes instead of sending it all at once?

thanks in advance!

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Anonymous posted one year agohi,i have to write a multithreaded connection oriented server using C/C++ and gcc.the server should be ableto handle multiple clients concurrently and simulate it for a minimum of ten concurrent clients

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{ TcpClient^ ClienteMBTCP; Thread^ hilocliente; int cantidad; int unidad; int referencia; String^ direccion; array<byte>^ registros; public: cliente(){ }public:

void Connect(String^ address, int port) {

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Awesome walk-through. This is the simplest explanation of C# Tcp that I have read. Very nicely done!

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maryam posted one year agothank you.

best regard for all friend

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Anonymous posted one year agohi every one, i have designed an instant news sending application for our customers.(using c# socket andasync methods.) The server accepts the connection and keeps them in a list as connected users. When anews is entered to database, the server program sends the news to the connected users. In here, the clientshould stay connected whole day to recieve the news when added. I want to ask is there any time limitationfor the connection to be alive. If 3 hours no news entered, then are the connections still alive and ready torecieve ? I am not asking to reconnect when disconnect conditions occurs. I have implemented thoseexceptional scenarios to reconnect. I searched too much but i could not find the answer i am looking for.

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Mike Hometchko posted one year agoFor those of you who are looking for a simple two-way communication resolution (and I've seen a ton ofposts requesting it) I'll post my code here.

Server

public class Server { private TcpListener tcpListener; private Thread listenThread;

public Server() { this.tcpListener = new TcpListener(IPAddress.Any, 3000); this.listenThread = new Thread(new ThreadStart(ListenForClients)); this.listenThread.Start(); }

private void ListenForClients() { this.tcpListener.Start();


//create a thread to handle communication //with connected client Thread clientThread = new Thread(new ParameterizedThreadStart(HandleClientComm));

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Client

Hope this helps!

Anton 10 months agoThank you very much, it really helped.

jack 6 months agoCan you give me example of the code, my code is not working well...

Thread clientThreadSend = new Thread(new ParameterizedThreadStart(HandleClientComm)); clientThread.Start(client); clientThreadSend.Start(client); } } private void HandleClientComm(object client) { TcpClient tcpClient = (TcpClient)client; TcpClient sendClient (TcpClient)client;

public class Client { TcpClient _tcpClient;

// Connects the client to a server at the specified // IP address and port. public void Connect(IPAddress address, int port) { _tcpClient = new TcpClient();

IPEndPoint serverEndPoint = new IPEndPoint(address, port);

_tcpClient.Connect(serverEndPoint);

// Create a thread to read data sent from the server. ThreadPool.QueueUserWorkItem( delegate { Read(); }); }

// Sends bytes to the server. public void Send(byte[] buffer) { _tcpClient.GetStream().Write( buffer, 0, buffer.Length);

_tcpClient.GetStream().Flush(); }

private void Read() {

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nikos posted one year agohello, im new in Promela and i have to simulate the TCP/IP connection management with flow control inPromela and i need help. thnx.

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Piyush Dixit posted one year agoHi, Thx for the code it is working great.

my problem is when i try to invoke tcp server Application from my wcf service. i get the exception..

please help..

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Anonymous posted one year agoQuote of the day:

'although in practice this is limited because you can only spawn so many threads before Windows will getupset'

Brilliantly put, Windows got upset with me recently as well.

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MindHACKer posted one year agoThis was very helpful, THANK YOU VERY MUCH.

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Rectangle rect= new Rectangle();rect.width = 10;rect.height = 10;rect.StrokeThickness = 1;rect.Stroke = Brushes.Black;

Point startPoint= new Point(54, 52);Canvas.SetLeft(rect,startPoint.X);Canvas.SetTop(rect,startPoint.X);canvas.Children.Add(rect);

Dispatcher.Invoke(new Action(() => { canvas.Children.Add(rect); }));

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Dilip Sharma posted one year agoHelp Full

Thanks For Post

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Anonymous posted one year agoMy program gives an error with the TcpClient.GetStream() command. It doesn't recognize this function. Am Imissing a declaration somewhere?

Anonymous one year agoNevermind, found the problem - I had the t in tcpClient capitalized.

GAWRRELL posted one year agoHy, i have tested the tutorial and i get an error A first chance exception of t type'System.Threading.WaitHandleCannotBeOpenedException' occurred in mscorlib.dll

Additional information: No handle of the given name exists.

Can anyone tell me how to fix this ?

Brandon Cannaday one year agoWhat line of code throws the exception?

Anonymous posted one year agoI used u r code but,

When I send some msgs from the client to server, i got an error " The calling thread cannot access this objectbecause a different thread owns it." on this line

" ASCIIEncoding encoder = new ASCIIEncoding(); txtContent.Textencoder.GetString(message, 0,bytesRead);"

help me.........

Am a beginner to the Socket pgming........

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Anonymous posted one year agoThank you for the detailed and simple explanation. This is what I needed.

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Anonymous posted one year agoFirst..thank you for the post! I am working with the DataMax printer that is connected directly to the PC vianetwork card. I have a TCP client tester that can send DPL commands to the printer and this part works well.However, I would like to add a Listner to get printer response. For example, when I send a command I shouldget back 3 blocks of eight bits each. My tester gets this reply but sometimes I need to send twice mycommand to get it. I think the listner that you are using would take care of it, but I am not sure how to use itin my app. My app is a simple windows form with one button, and response txt box.

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Here is the link to the code I used in my app: http://msdn.microsoft.com/en-us/library/system.net.sockets.tcpclient.aspx

I made small changes to it as my app shows a form:

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Anonymous posted one year agoPlease note that NetworkStream.Flush() has no effect on the data in the stream.

http://msdn.microsoft.com/en-us/library/system.net.sockets.networkstream.flush.aspx

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LuisF posted one year agoHi that´s a great explanation and a great code thank you very much. I have a question: How to get the IPaddress of the connected client?, I have looked to the tcpClient members but couldn't find any related optionthere and don´t know where could i get it

void SendCommandToNetworkPrinter(String server, String message) { try {

// Create a TcpClient. // Note, for this client to work you need to have a TcpServer // connected to the same address as specified by the server, port // combination. Int32 port = System.Convert.ToInt32(txtPortId.Text); TcpClient client = new TcpClient(server, port);

// Translate the passed message into ASCII and store it as a Byte array. Byte[] data = Encoding.ASCII.GetBytes(message);//System.Text.Encoding.ASCII.GetBytes(message);

// Get a client stream for reading and writing. Stream stream = client.GetStream();

//NetworkStream stream = client.GetStream();

// Send the message to the connected TcpServer. stream.Write(data, 0, data.Length);

stream.Flush();

//Console.WriteLine("Sent: {0}", message); //MessageBox.Show("Sent:" + message); txtReply.Text += "SENT:" + message;

// Receive the TcpServer.response.

// Buffer to store the response bytes. data new Byte[256];

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Thank a bunch!

LuisF one year agoOhh men, I´m not native English speaker, I have always thought that "Thanks a bunch" was thanks alot, I just searched for for curiosity and found it was sarcastic sorry men, you know i meant thanks alot!

Danish Coder posted one year agoMy new best friend ;-) Thx m8

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Gio posted one year agoVery good essential example !

Thanks a lot !

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Anonymous posted one year agoHello, Me I am having problem to handle an exception at the line NetworkStream clientStream =tcpClient.GetStream();

A NullPointerException..

I try to catch it by doing this: try{ NetworkStream clientStream = tcpClient.GetStream(); }catch {Console.WriteLine("An error /..."); } I can catch the exception but my program can not continue. it breaks atthis level. How can I solve it??

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Dias posted one year agoVery good post

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rechim posted one year agohey i have a question. i send a resuest from client to server, then the server send back to the client ananswer. how to catch the servers respond into client? its the same thing like the server catch the messagefrom clients? or what? thx

Manish Ta 9 months agohave you got your answer, if yes please tell me.

any other help are welcome

this is really urgent

thanks in advance mailid : [email protected]

Gratefule posted 12 months agoReddest: Just echoing what many others before me have stated, "EXECELLENT!". Too bad Redmondcannot find authors with your technical and explanation skills - I know, I searched many hours through MSDN


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and came up empty. Gee, and I even pay for an MSDN subsription. Go figure!

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Andy posted 12 months agoHi Reddest, thank you for a great example. I do have one problem that I hope you (or someone else) canhelp me with. I've used your example to write a client and a server and it works great when both are runningon the same pc, but when I try to run the client on another PC, then I cannot connect (this code line timesout: client.Connect(serverEndPoint);) to the server. I'm on a corporate LAN and I've opened ports in thefirewall on both PC's.

Any help will be greatly appreciated!

Here is some simplified code that I use to test the connection:

Andy 12 months agoOk, I found a solution. The server runs as a service and I needed to setup the inbound rule in thefirewall as described here:

http://technet.microsoft.com/en-us/library/cc947797(v=ws.10)

//Client:

using (TcpClient client = new TcpClient()){ IPEndPoint serverEndPoint = new IPEndPoint(IPAddress.Parse(ServerIp), 14011); //client.Client. client.Connect(serverEndPoint); using (NetworkStream clientStream = client.GetStream()) { Console.WriteLine("Connected? :" + client.Connected.ToString()); ASCIIEncoding encoder = new ASCIIEncoding(); byte[] buffer = encoder.GetBytes("IDLE");

clientStream.Write(buffer, 0, buffer.Length);

clientStream.Flush();

clientStream.ReadTimeout = 29000;

byte[] message = new byte[4096]; int bytesRead = 0;

bytesRead = clientStream.Read(message, 0, 4096);

string msg = encoder.GetString(message, 0, bytesRead);

Console.WriteLine("Message: " + msg); return; }}

//Server:TcpListener tcpListener = new TcpListener(IPAddress.Any, 14011);NetworkStream clientStream null;

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The "normal" access to the firewall (Ctrl panel => win firewall) was not enough and the service's SIDtype was set to NONE instead of UNRESTRICTED.

Anonymous posted 11 months agoI am a noob and completely new to C#. I am more familiar with android but I need a server like this. Cansomeone post more exact instructions on creating this entire thing from the beginning. He did a good job ofincluding the code but I have no idea as to where the code needs to be out in the project.

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Sam Pearson posted 11 months agoHi, The Reddest, I've got a question about this. Suppose I've got this example running in its backgroundthread behind a Windows Form. When I close the form, my program no longer exits, because the thread iswaiting on tcpListener.AcceptTcpClient(). How can I solve this problem? I want my whole program to exitwhen I close the form. I tried calling listenThread.Abort(), but that doesn't work.

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Anonymous posted 10 months agonice article

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Anonymous posted 10 months agoIm getting this error: Unable to read data from the transport connection: An existing connection was forciblyclosed by the remote host.

At this line:

bytesRead = clientStream.Read(message, 0, 4096);

What am I doing wrong? The server and the client are my local machine.

Anonymous-No2 9 months agoI get the same error also, any solution on this?

Manish Ta posted 9 months agoThis is nice example

I have a question

i am able to send data from client to server, now server send back data to client how can i read this data sentby server to client.

thanks in advance

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Chuck Bland posted 4 months agoHas anyone implemented the change/suggestion from David S with the async handling? I think I understandwhat to do with it. It would help to see his solution completed.

Specifically, does the thread handling in the original post remain the same, and would be placed where DavidS comments "//Handle the client connection here" ?

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Gal Kos posted one month agoHey, Brandon. I have achieved the sending message client -> server and actually connecting many clientssimultaneously. But what I want to do is i.e. connect 2 clients and make them chat between themselves. Andif 3rd client connects - then so he starts chatting with both other clients.

The thing is that I don't know how to distinguish between the different clients' threads. This is my function:

where I have the array for storing clients objects

and after starting every thread I do this:

private void HandleClientComm(object client) { TcpClient tcpClient = (TcpClient)client; NetworkStream stm = clientList[n].GetStream(); msg = new TheMessage();

while (true) { Byte[] bSize = new Byte[sizeof(Int32)]; stm.Read(bSize, 0, bSize.Length);

Byte[] bData = new Byte[BitConverter.ToInt32(bSize, 0)]; stm.Read(bData, 0, bData.Length);

msg = XmlRefactorServer.ByteArrayToObject<TheMessage>(bData); String str = msg.Message; Console.WriteLine(str); stm.Flush();

// send back to client msg.Message = str; Byte[] bDataBack = XmlRefactorServer.ObjectToByteArray<TheMessage>(msg);

stm = clientList[n].GetStream();

Byte[] bSizeBack = BitConverter.GetBytes(bDataBack.Length);

stm.Write(bSizeBack, 0, bSizeBack.Length); stm.Write(bDataBack, 0, bDataBack.Length); stm.Flush();

}

tcpClient Close();

TcpClient[] clientList = new TcpClient[100];private int n = 0;

TcpClient client = this.tcpListener.AcceptTcpClient(); if (n == 0)

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So yeah... how do I make the distinguishing of the different clients (client threads)?

P.S. I have created a protocol for data transfer so don't worry about that.

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{ clientList[0] = client; n++; } else { clientList[n] = client; }

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