lect-5 java emailing

8/6/2019 Lect-5 Java Emailing

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Contents Advanced Socket Programming

Socket Timeouts

Interruptible Sockets Half-close

Internet Address

Java Mail Messaging System

1



Socket Timeouts Problem:If the host is unreachable,

then your application waits for a long

time or read methods will block untildata are available so.

Java offers Socket.setSoTimeout tocontrol how long you are willing to

wait for a read to complete.

Decide what time out value isreasonable for your application.

2



Then call the setSoTimeout method to set atime out value(in milliseconds)

Socket s=new Socket(«.);

S.setSoTimeout(10000);//time out after 10seconds.

If the time out value has been set for asocket,then all subsequent read and write

operations throw a SocketTimeoutExceptionwhen the time out has been reached before theoperation has completed its work.

3



Case-2: The constructor Socket(String host,int port)can block indefinitely until an initial connection to thehost is established.

Solution: First construct an unconnected socket andthen connecting it with a timeout.

Socket s=new Socket();

s.connect(new InetSocketAddress(host,port),timeout);

4



Interruptible sockets Gives user an option to simply cancel

a socket connection that does not

appear to produce results. For ex in a client server application if

the server pretends to be busy anddoes send any reply to the

client..client can click cancel button toterminate the connection.

5



To interrupt a socket operation ,SocketChannelis used,a feature of the java.nio package.

SocketChannel

channel=SocketChannel.open(newInetSocketAddress(host,port));

Whenever a thread is interrupted during anopen ,read or write operation ,the operation

does not block but is terminated with anexception

6



Half-close When a client program sends a request to the

server, server needs to be able to determinewhen the end of request occurs.

This can be accomplished by closing the outputstream of a socket, thereby indicating to theserver the end of the request data, but keepingthe input stream open to read the response

coming from server. So if you want to shut down only half of the

connection, either input or output -the

shutdownInput() and shutdownOutput method

7



Let you close only half of theconnection.

This down not close the socket

8



Internet Address InetAddress class ->used to convert between host

names and internet addresses.

InetAddress

address=InetAddress.getByName(³hostname´);

Returns an Inetaddress object that encapsulates thesequence of four bytes

like 132.163.4.104.

To access the bytes use getAddress method

Byte[] addressbytes=address.getAddress();

9



10

Java Mail Messaging System



11

E-Mail Messaging System

Java e-mail messaging system is composed of mail

clients and mail servers.

An e-mail client is a GUI based application installed onuser¶s machine. The most popular are netscapecommunication and MS outlook.

An e-mail server is responsible for routing messages to

their destination and also storing messages until theuser receives them:

SMTP defines the process for sending e-mail in a reliableand efficient manner.

POP3 defines mechanism for retrieving messages from a

mail server. The POP3 protocol identifies the user andthe password and retrieves only those messages for thegiven user.



12

Process of E-Mail Transmission

E-mail Sender

E-mail Recipient

SMTP Server

POP3 Server

messages



13

Anatomy of an E-mail Message

An e-mail message is composed of two major sections.Headers containing a set of attributes and body( content).

The header contains the information about the message, suchas the sender, recipient, subject and time stamp.

The actual content of the message is contained in the bodypart.

Message

HeaderAttributes

Content(Body)

Sender, recipient, subject



14

Electronic MailThree major components:

user agents

mail servers

simple mail transferprotocol: SMTP

User Agent

composing, editing, readingmail messages

e.g: Outlook, elm, NetscapeMessenger

outgoing, incomingmessages stored on server

user mailbox

outgoingmessage queue

mailserver

useragent

useragent

useragent

mail

server

useragent

useragent

mailserver

useragent

SMTP

SMTP

SMTP



15

Electronic Mail: mail servers

Mail Servers

mailbox containsincoming messages foruser

message queue of outgoing (to be sent)mail messages

SMTP protocol betweenmail servers to send

email messages client: sending mail

server

³server´: receivingmail server

mailserver

useragent

useragent

user

agent

mail

server

useragent

useragent

mailserver

useragent

SMTP

SMTP

SMTP



16

Electronic Mail: SMTP uses TCP to reliably transfer email message from

client to server, port 25

direct transfer: sending server to receiving server

three phases of transfer

handshaking (greeting)

transfer of messages

closure

command/response interaction

commands: ASCII text response: status code and phrase

messages must be in 7-bit ASCII



17

Scenario: A sends message to B

1) A uses UA to composemessage and providesB¶s Email addressb@@bits-pilani.ac.in

2) A¶s UA sends message toher mail server;message placed inmessage queue

3) Client side of SMTPopens TCP connectionwith B¶s mail server

4) SMTP client sends A¶smessage over the TCPconnection

5) B¶s mail server placesthe message in Bob¶smailbox

6) Bob invokes his useragent to read message

useragent

mailserver

mailserver user

agent

1

2 3 4 56



18

Try SMTP interaction for yourself:

telnet servername 25

see 220 reply from server

enter HELO, MAIL FROM, RCPT TO, DATA, QUIT

commands

above lets you send email without using emailclient (reader)



19

Sample SMTP interactionS: 220 bitsmail01.bits-pilani.ac.inC: HELO bitsmail01.bits-pilani.ac.in

S: 250 Hello bitsmail01.bits-pilani.ac.in, pleased to meet you

C: MAIL FROM : < [email protected] >

S: 250 r [email protected]... Sender ok

C: R CPT TO: < [email protected]>

S: 250 [email protected] ... Recipient ok

C: DA T A

S: 354 Enter mail, end with "." on a line by itself

C: Do you like ketchup?

C: How about pickles?

C: . S: 250 Message accepted for delivery

C: QUIT

S: 221 bitsmail01.bits-pilani.ac.in closing connection



Java Mail API

The JavaMailAPI provides classes thatmodel a mail system.

Java Mail API is a simple and handy toolfor implementing mail/messagingfunctionality in your applications.

The JavaMail API provides a set of

abstract classes that model a mailsystem. The API provides a platformindependent and protocol independentframework to build Java technology-based

mail and messaging applications20



Core classes of this API are

javax.mail.Session, javax.mail.Store,

javax.mail.Transport, javax.mail.Folder, and javax.mail.Message.

21



javax.mail.Session

The javax.mail.Session class is thetop-level entry class for the Java Mail

API, and its most commonly usedmethods provide the ability to controland load the classes that representthe service provider implementations

(SPI) for various mail protocols

22



javax.mail.Store

The javax.mail.Store class isimplemented by a service provider,

such as a POP Mail implementationdeveloper, and allows for read, write,monitor, and search access for aparticular mail protocol.

23



javax.mail.Transport

The javax.mail.Transport class isanother provider-implemented class

and is used for sending a messageover a specific protocol.

24



javax.mail.Folde

The javax.mail.Folder class isimplemented by a provider; it gives

hierarchical organization to mailmessages and provides access to e-mail messages in the form of

javax.mail.Message class objects

25



javax.mail.Message

The javax.mail.Message class isimplemented by a provider and

models all the details of an actual e-mail message, such as the subjectline, sender/recipient e-mail address,sent date, and so on

26



27

Example Program

import javax.mail.*;import javax.mail.internet.*;

public class QuickMailText {

/*** Sends a simple text e-mail message.*

* @param smtpHost name of the SMTP mail server* @param from e-mail address of the sender* @param to e-mail address of the recipient* @param subject subject of the e-mail message* @param messageText the actual text of the message** @throws javax.mail.MessagingFormatException problems

sending message*/public static void sendMessage(String smtpHost,String from, String to,String subject, String messageText)throws MessagingException {



28

Step 1: Configure the mail session

System.out.println("Configuring mail session for: " +smtpHost);

java.util.Properties props = new java.util.Properties();

props.setProperty("mail.transport.protocol", "smtp");

props.setProperty("mail.host", " mail.itmindia.edu ");

props.setProperty("mail.user", "emailuser");Session mailSession =Session.getDefaultInstance(props);



Step 2: Construct the message

System.out.println("Constructing message - from=" +from + " to=" + to);

InternetAddress fromAddress = newInternetAddress(from);

InternetAddress toAddress = new InternetAddress(to);MimeMessage testMessage = newMimeMessage(mailSession);

testMessage.setFrom(fromAddress);testMessage.addRecipient(javax.mail.Message.RecipientT

ype.TO, toAddress);

testMessage.setSentDate(new java.util.Date());testMessage.setSubject(subject);testMessage.setText(messageText);System.out.println("Message constructed");



Step 3: Now

send the message

Transport transport =

mailSession.getTransport();transport.connect();

transport.send(testMessage);

System.out.println("Messagesent!");

}



31

public static void main(String[] args) {if (args.length != 3) {System.out.println("Usage: java QuickMailText <smtphost> <from>

<to>");

System.exit(1);}

String smtpHost = args[0];String from = args[1];String to = args[2];String subject = "Test Message - quickmail_text";StringBuff er theMessage = new StringBuff er();

theMessage.append("H

ello,\

n\

n");theMessage.append("Hope all is well.\n");theMessage.append("Cheers!");try {QuickMailText.sendMessage(smtpHost, from, to, subject,

theMessage.toString());}catch (javax.mail.MessagingException exc) {

exc.printStackTrace();}

}}



32

R unning Java Mail API Programs(A) Sending E-Mail

---------------

c:\>java <programname> <smtphost> <from> <to>

OR

java <programname> <smtphost> <from> <to> <f iletoattach>

For example,

java QuickMailText mail.itmindia.edu [email protected] [email protected]

OR

java QuickMailAttach mail.itmindia.edu [email protected] [email protected]



33

(B) R etrieving all E-Mails

c:\>java -Dhttp.proxyHost=192.168.0.1 -Dhttp.proxyPort=90

<programname> <pop3host> <user> <password>

For example,

c:\>java -Dhttp.proxyHost=192.168.0.1 -Dhttp.proxyPort=90MessageList 192.168.0.1 rimpy abc

(C) Viewing Message Contents of an E-Mail-------------------------------------

c:\>java -Dhttp.proxyHost=192.168.0.1 -Dhttp.proxyPort=90<programname> <pop3host><user> <password> <messagenumber>

For example,

c:\>java -Dhttp.proxyHost=192.168.0.1 -Dhttp.proxyPort=90MessageView 192.168.0.1 rimpy abc 2

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