networking in .net (1) lecture notes/week 11-2.pdf · 2006-11-23 · 1 networking in .net (1) these...

1

Networking in .NET (1)

These slides are meant to be for teaching purposes only and only for the students that are registered in CSE4413 and should not be published as a

book or in any form of commercial product, unless written permission is obtained.

2

Client-Server model

• All communication (SOAP exchanges, Web applications, etc) is done via “low level” socket programming.

• The general idea is:– A computer that acts as “Server” makes its

service(s) available at a particular port.– Other computers that know about this server

can then request connections and receive the service(s).

3

Typical Client-Server communication scenario

• Server1. Initiate “service available”

at a particular port.2. Wait for client request for

connection.3. Once client’s request is

received: a) Establish connectionb) Establish communication

stream (so that can send and receive data).

4. Provide service5. Close connection6. Go to step 2 (wait for

client’s request for connection).

• Client1. Request connection from

server (must know: server “name” (IP address) and port # at which service is available).

2. (If connection is established) establish communication stream (so that can send and receive data).

3. Get the service.

4

Typical Client-Server communication scenario

Server Client

80

5555

…

port

client = new TcpClient( );

client.Connect( "localhost", 5555);

cs= client.GetStream();

reader = new BinaryReader( cs) ;

writer = new BinaryWriter( cs) ;

server = new TcpListener( 5555);

server.Start();

c = server.AcceptSocket();

ss = new NetworkStream(c);

reader = new BinaryReader(ss);

writer = new BinaryWriter(ss);

Initiate “service available” at port 5555. Wait for client request for connection.

Establish connection with client; Establish communication stream (so that can send and

receive data).

Request connection from server with IP localhost, at port 5555

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An application

The server

The client

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After the client connects, the server sends a message and closes the

connection.

The client receives and displays the

message.

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Designer view :: Server

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Code structure :: Server

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The code :: Serverusing System;using System.Drawing;using System.Collections;using System.ComponentModel;using System.Windows.Forms;using System.Data;

using System.Threading;using System.Net.Sockets;using System.IO;

namespace WindowsApplication2Server{

public class Form1 : System.Windows.Forms.Form{

private System.Windows.Forms.Button button1;private System.Windows.Forms.Label label1;

private Socket conn; // the client

private NetworkStream socketStream; private BinaryReader reader;private BinaryWriter writer; private Thread readThread;private System.Windows.Forms.Label label2;private System.Windows.Forms.Button button2;

Needed for threading, networking and message

exchanges.

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..private System.ComponentModel.Container components = null;

public Form1(){

InitializeComponent();}

//…[STAThread]static void Main() {

Application.Run(new Form1());}

private void button1_Click(object sender, System.EventArgs e){

readThread = new Thread( new ThreadStart( RunServer ) );readThread.Start();

label2.Text = "calling run server";}

public void RunServer() {

TcpListener listener ;

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…try {

label2.Text += "\r\nTrying to establish server at port 5555";// create listener (the server)

listener = new TcpListener( 5555); // listens at port 5555label2.Text += "\r\nEstablished server at port 5555";

// server waits for connection

listener.Start();label2.Text += "\r\nestablished connection and waiting for client...";

// establish connection upon client's requestwhile ( true ) {

conn = listener.AcceptSocket(); // establish connectionlabel2.Text += "\r\n .... client connected!!!";

// create communication steam

socketStream = new NetworkStream( conn);label2.Text += " opening communication stream ...";

// attach a reader and a writer to the stream

writer = new BinaryWriter( socketStream);label2.Text += "\r\n ... ... opened writer";

reader = new BinaryReader( socketStream);label2.Text += "\r\n ... ... opened reader";

writer.Write( "(FROM SERVER) -- connection established");writer.Write( "\r\n(Server)-- connection closing...");label2.Text += "\r\n ... sent message to client!";

writer.Close();label2.Text += " ...closed connection";

} }catch ( Exception ex) {

MessageBox.Show( ex.ToString());}

}

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…/


try {

writer.Close();reader.Close();socketStream.Close();conn.Close();

}catch ( Exception ee) {

MessageBox.Show( ee.ToString());}Application.Exit();

}}}

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Designer view :: Client

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Code structure :: Client

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The code :: Clientusing System;using System.Drawing;using System.Collections;using System.ComponentModel;using System.Windows.Forms;using System.Data;


namespace WindowsApplication1Client{

/// <summary>/// Summary description for Form1./// </summary>public class Form1 : System.Windows.Forms.Form{

private System.Windows.Forms.Button button1;private System.Windows.Forms.Label label1;private System.Windows.Forms.Button button2;private System.ComponentModel.Container components = null;

public Form1(){}

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…/// <summary>/// Clean up any resources being used./// </summary>

//…private void InitializeComponent(){

this.button1 = new System.Windows.Forms.Button();

this.label1 = new System.Windows.Forms.Label();this.button2 = new System.Windows.Forms.Button();this.SuspendLayout();// // button1// this.button1.Location = new System.Drawing.Point(32, 32);this.button1.Name = "button1";this.button1.TabIndex = 0;this.button1.Text = "Start Client";this.button1.Click += new System.EventHandler(this.button1_Click);// // label1// this.label1.Location = new System.Drawing.Point(16, 72);this.label1.Name = "label1";this.label1.Size = new System.Drawing.Size(352, 216);this.label1.TabIndex = 1;this.label1.Text = "label1";// // button2// this.button2.Location = new System.Drawing.Point(168, 40);this.button2.Name = "button2";this.button2.TabIndex = 2;this.button2.Text = "Exit Client";this.button2.Click += new System.EventHandler(this.button2_Click);// // Form1// this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);this.ClientSize = new System.Drawing.Size(392, 301);this.Controls.Add(this.button2);this.Controls.Add(this.label1);this.Controls.Add(this.button1);this.Name = "Form1";this.Text = "Form1";this.ResumeLayout(false);

}#endregion

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…

[STAThread]static void Main() {


private Thread readThread;


readThread = new Thread( new ThreadStart ( RunClient));readThread.Start();

}

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…private NetworkStream clientStream;private BinaryWriter writer;private BinaryReader reader;

public void RunClient() {

TcpClient client;

try {

label1.Text = "Attempting connection to server ...";

client = new TcpClient( );client.Connect( "localhost", 5555);

label1.Text += "\r\n" + "connection established!";// establish a data exchange capable stream.

clientStream = client.GetStream();// hookup reader and writer to streams

reader = new BinaryReader( clientStream) ;writer = new BinaryWriter( clientStream) ;

bool gotServerMessage = false;

string message = "";

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…/

do {

message = reader.ReadString();

label1.Text += "\r\n" + " received message from server!";

label1.Text += "\r\n the message :: " + message;

gotServerMessage = true;

} while ( !gotServerMessage );}catch ( Exception ee ) { }

}


Application.Exit();}

}}

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Threads

• A thread is a “lightweight” process. • Processes run within their own separate space

and communicate with each other by exchanging messages (since they do not share any space).

• Threads run within a process and communicate with each other by sharing memory space. (i.e. by being able to access the same space as other fellow threads).

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P1 (process)

T1 (thread)

T2

T3

P2 (process)

T4 T5

Memory space

Object, shared by T1, T2, T3

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Threads in C#

• Threads in C# are done similar to Java, but with delegates.

• C# has a predefined delegate class ThreadStart for this purpose.• C# has predefined method Start() that starts the threads.• Java:

– Have thread objects containing method run()• C#:

– Have methods Xrun(), each of which is hooked to a separate thread using C#’s ThreadStart delegate. The names of these methods are programmer chosen.

– Each such method contains the code that is to be executed under a separate thread.

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Threads in C#using System;using System.Threading;namespace ConsoleApplication4{class Test {static void printA () // to run on thread t1{ int count = 0;

while (true) { Console.Write("A"); count++; if (count % 10000 ==0) break; }

}

static void printB () // to run on thread t2{ int count = 0;

while (true) { Console.Write("B");count++; if (count % 10000 ==0) break; }

}

public static void Main () {

Thread t1 = new Thread(new ThreadStart(printA));Thread t2 = new Thread(new ThreadStart(printB));t1.Start(); t2.Start();

}}}

Hook the desired

methods to corresponding

threads.

Start the threads; method Start() is a predefined method in C#

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Notice the interleaving …

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Threads in C#using System;using System.Threading;

namespace ConsoleApplication3{

class SimpleThread{

// method ARun to run on thread t1public void ARun() {

for (int i=0; i<1000; i++) {

Console.Write(" [A "+i+ "]");}

}// method BRun to run on thread t2

public void BRun() {

for (int i=0; i<1000; i++) {

Console.Write(" [B "+i+ "]");}

}

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Threads in C# … // method CRun to run on thread t3public void CRun(){

for (int i = 0; i < 1000; i++){

Console.Write(" [C "+i+ "]");}

}public void go() { // ThreadStart is a predefined C# delegate, for threads.ThreadStart threadDelegate1 = new ThreadStart( ARun);ThreadStart threadDelegate2 = new ThreadStart( BRun);ThreadStart threadDelegate3 = new ThreadStart( CRun);

Thread t1 = new Thread( threadDelegate1);Thread t2 = new Thread( threadDelegate2);Thread t3 = new Thread( threadDelegate3);

t1.Start();t2.Start();t3.Start();

}

static void Main (string[] args){

new SimpleThread().go();}

}}

Start the threads; method Start() is a predefined method in C#

Create the threads

Hook the desired

methods to corresponding threads

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…

…

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A multithreaded server• It is realistic that a server serves more than one client at

a time. (it is not realistic that a server serves one client from start to end, while other clients wait to be connected).

• A multithreaded server is a server which accepts clients’ requests for connection and accepts more than one client at a time. Consequently, the server serves the clients, concurrently.

• The concurrency is achieved by the server assigning each client to a separate thread, and then start (and run) all threads. (The multithreaded capabilities of the underlying operating system then allow for this multithreading to be achieved.)

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Example

The client sends to the server a string (“A”, or “B”, or “C”), as many times as

specified in the textbox.

The server connects with the 3 clients,

receives the strings sent by each client and displays them, using 3

different threads.

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Running

• To start the application, enter numbers in the textbox of each client and press the start button of the server and of all the clients.

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Running … server started and it has displayed some of the received strings


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A bit later …


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The clients …

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The code structure :: Server

serviceThreads is an array of Thread. Each client is associated with one

serviceThread.

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The code :: Server

using System;using System.Drawing;using System.Collections;using System.ComponentModel;using System.Windows.Forms;using System.Data;


namespace WindowsApplication2ServerMultiThreaded{


private System.Windows.Forms.Button button1;private System.Windows.Forms.Button button2;private System.Windows.Forms.TextBox textBox1;/// <summary>/// Required designer variable./// </summary>private System.ComponentModel.Container components = null;

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…public Form1(){

/// <summary>/// Clean up any resources being used./// </summary>protected override void Dispose( bool disposing ){

if( disposing ){

if (components != null) {

components.Dispose();}

}base.Dispose( disposing );

}

#region Windows Form Designer generated code/// <summary>/// Required method for Designer support - do not modify/// the contents of this method with the code editor./// </summary>private void InitializeComponent(){

//…

}#endregion

[STAThread]static void Main() {


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…

private NetworkStream [] socketStream = new NetworkStream[3];

private BinaryReader [] reader = new BinaryReader[3];

private BinaryWriter [] writer = new BinaryWriter[3];


private Thread [] serviceThreads = new Thread[3];

private Socket [] conn = new Socket[3]; // the clients (assume 3 clients)


readThread = new Thread( new ThreadStart( RunServer ) );readThread.Start();

textBox1.Text = "calling run server";

}

One stream set per client.

One thread per client

Main server thread.

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…public void RunServer() {

TcpListener listener ; try {

textBox1.Text += "\r\nTrying to establish server at port 5555";// create listener (the server)

listener = new TcpListener( 5555); // listens at port 5555textBox1.Text += "\r\nEstablished server at port 5555";

// server waits for connection

listener.Start();textBox1.Text += "\r\nestablished connection and waiting for client...";

// establish connection upon client's requestwhile ( true ) {

conn[0] = listener.AcceptSocket(); // establish connectiontextBox1.Text += "\r\n .... client 0 connected!!!";



// create communication steam

socketStream[0] = new NetworkStream( conn[0]);textBox1.Text += " opening communication stream ...0";

// attach a reader and a writer to the stream



writer[0] = new BinaryWriter( socketStream[0]);textBox1.Text += "\r\n ... ... opened writer 0 ";

Connect to each client.

Establish stream to

each client.

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…writer[1] = new BinaryWriter( socketStream[1]);textBox1.Text += "\r\n ... ... opened writer 1 ";

writer[2] = new BinaryWriter( socketStream[2]);textBox1.Text += "\r\n ... ... opened writer 2 ";

reader[0] = new BinaryReader( socketStream[0]); textBox1.Text += "\r\n ... ... opened reader 0 ";



serviceThreads[0] = new Thread( new ThreadStart( ServiceA));serviceThreads[1] = new Thread( new ThreadStart( ServiceB));serviceThreads[2] = new Thread( new ThreadStart( ServiceC));

serviceThreads[0].Start();serviceThreads[1].Start();serviceThreads[2].Start();

} // while} //try catch ( Exception ex) {

MessageBox.Show( ex.ToString());}

} // end RunServer

Put each client on a separate thread.

Start the client threads.

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…public void ServiceA ()

{int count=0;while (true) {

textBox1.Text += reader[0].ReadString() + ".";count++;

}}

public void ServiceB ()


textBox1.Text += reader[1].ReadString() + "." ;count++;

}}

public void ServiceC ()


textBox1.Text += reader[2].ReadString() + ".";

count++;}

}

Read incoming message from each client.

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…/


readThread.Abort();serviceThreads[0].Abort();serviceThreads[1].Abort();serviceThreads[2].Abort();


}}

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The code structure :: Client A

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The code :: Client Ausing System;using System.Drawing;using System.Collections;using System.ComponentModel;using System.Windows.Forms;using System.Data;


namespace WindowsApplication2ClientA{

public class Form1 : System.Windows.Forms.Form{

private System.Windows.Forms.Button button1;private System.Windows.Forms.Button button2;private System.Windows.Forms.TextBox textBox1;private System.Windows.Forms.Label label1;private System.Windows.Forms.TextBox textBox2;/// <summary>/// Required designer variable./// </summary>private System.ComponentModel.Container components = null;

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…//…

private void InitializeComponent(){

//…}

/// <summary>/// The main entry point for the application./// </summary>[STAThread]static void Main() {





}

private NetworkStream clientStream;private BinaryWriter writer;private BinaryReader reader; Main client

thread.

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…/public void RunClient() {

TcpClient client;try {

textBox1.Text = "Attempting connection to server ...";

client = new TcpClient( );client.Connect( "localhost", 5555);textBox1.Text += "\r\n" + "connection established!";

// establish a data exchange capable stream.

clientStream = client.GetStream(); // hookup reader and writer to streamsreader = new BinaryReader( clientStream) ;writer = new BinaryWriter( clientStream) ;int count = 0; int howmanyWrites = Int32.Parse( textBox2.Text);for (int i = 0; i < howmanyWrites; i++){

writer.Write("A");textBox1.Text += "\r\n" + " written message to server! " + count;count++;

} }catch ( Exception ee ) { }

} // RunClient


Application.Exit();}} // end class ClientA}

Establish communication

stream.

Connect to server.

Send message to server.

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The code structure :: Client B

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The code :: Client Busing System;using System.Drawing;using System.Collections;using System.ComponentModel;using System.Windows.Forms;using System.Data;


namespace WindowsApplication2ClientB{


private System.Windows.Forms.Button button1;private System.Windows.Forms.Button button2;private System.Windows.Forms.TextBox textBox1;private System.Windows.Forms.Label label1;private System.Windows.Forms.TextBox textBox2;/// <summary>/// Required designer variable./// </summary>private System.ComponentModel.Container components = null;

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…//…

static void Main() {





}



private NetworkStream clientStream;private BinaryWriter writer;private BinaryReader reader;

int howManyWrites = 0;

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…/public void RunClient() {



client = new TcpClient( );client.Connect( "localhost", 5555);textBox1.Text += "\r\n" + "connection established!";

// establish a data exchange capable stream.

clientStream = client.GetStream();reader = new BinaryReader( clientStream) ;writer = new BinaryWriter( clientStream) ;

int count = 0;

howManyWrites = Int32.Parse( textBox2.Text);

for (int i = 0; i < howManyWrites; i++){

writer.Write("B");textBox1.Text += "\r\n" + " written message to server! " + count;count++;


}

} // end class ClientB}

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The code structure :: Client C

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The code :: Client Cusing System;using System.Drawing;using System.Collections;using System.ComponentModel;using System.Windows.Forms;using System.Data;

using System.Net.Sockets;using System.Threading;using System.IO;

namespace WindowsApplication2ClientC{


private System.Windows.Forms.Button button1;private System.Windows.Forms.Button button2;private System.Windows.Forms.TextBox textBox1;private System.Windows.Forms.TextBox textBox2;private System.Windows.Forms.Label label1;/// <summary>/// Required designer variable./// </summary>private System.ComponentModel.Container components = null;

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…//…static void Main() {


private void Form1_Load(object sender, System.EventArgs e){

}private Thread readThread;



}

private NetworkStream clientStream;private BinaryWriter writer;private BinaryReader reader;

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…public void RunClient() {



client = new TcpClient( );client.Connect( "localhost", 5555);textBox1.Text += "\r\n" + "connection established!";// establish a data exchange capable stream.

clientStream = client.GetStream(); reader = new BinaryReader( clientStream) ;writer = new BinaryWriter( clientStream) ;int count = 0; int howManyWrites = Int32.Parse( textBox2.Text);for (int i = 0; i < howManyWrites; i++){

writer.Write("C");textBox1.Text += "\r\n" + " written message to server! " + count;count++;


}


Application.Exit();}}}

networking in .net (1) lecture notes/week 11-2.pdf · 2006-11-23 · 1 networking in .net (1) these...

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