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Socket Programming

Jignesh Patel

Palanivel Rathinam

connecting processes

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Overview

Introduction to Sockets A generic Client-Server application References

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Introduction to Sockets

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Introduction to Sockets

Why Sockets? Used for Interprocess communication.

The Client-Server model Most interprocess communication uses client-server model Client & Server are two processes that wants to communicate with each

other The Client process connects to the Server process, to make a request for

information/services own by the Server. Once the connection is established between Client process and Server

process, they can start sending / receiving information.

What are Sockets? End-point of interprocess communication. An interface through which processes can

send / receive information

Socket

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Introduction to Sockets

What exactly creates a Socket? tuple

What makes a connection?

{Source , Destination } i.e. sourcesocket destination socket pair uniquely identifies a connection.

Example

Server

Client

Client

192.168.0.1

192.168.0.2

192.168.0.2

80

1343

5488

Client192.168.0.31343

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Introduction to Sockets

Socket Types STREAM uses TCP which is reliable, stream oriented protocol

DATAGRAM uses UDP which is unreliable, message oriented protocol

RAW provides RAW data transfer directly over IP protocol (no transportlayer)

Sockets can use unicast ( for a particular IP address destination)

multicast ( a set of destinations 224.x.x.x)

broadcast (direct and limited)

Loopback address i.e. 127.x.x.x

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A generic Client-Server application

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A generic TCP application

algorithm for TCP client Find the IP address and port number of server Create a TCP socket Connect the socket to server (Server must be up and listening for new

requests)

Send/ receive data with server using the socket Close the connection

algorithm for TCP server Find the IP address and port number of server Create a TCP server socket

Bind the server socket to server IP and Port number (this is the port to whichclients will connect)

Accept a new connection from client returns a client socket that represents the client which is connected

Send/ receive data with client using the client socket

Close the connection with client

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A generic UDP application

algorithm for UDP client Find the IP address and port number of server Create a UDP socket Send/ receive data with server using the socket Close the connection

algorithm for UDP server Find the IP address and port number of server Create a UDP server socket Bind the server socket to server IP and Port number (this is the port to which

clients will send) Send/ receive data with client using the client socket

Close the connection with client

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References

Man pages in LinuxAccesssible through following command man 2 E.g. man 2 socket

Unix network programming by Richard Stevens Beejs guide to Network Programming

http://beej.us/guide/bgnet/ The Java Tutorial Custom Networking

http://java.sun.com/docs/books/tutorial/networking/ Lecture notes of cs423 from Dr. Bob Cotter

http://www.sce.umkc.edu/~cotterr/cs423_fs05/cs423_fs05_lectures.html

http://beej.us/guide/bgnet/http://java.sun.com/docs/books/tutorial/networking/http://www.sce.umkc.edu/~cotterr/cs423_fs05/cs423_fs05_lectures.htmlhttp://www.sce.umkc.edu/~cotterr/cs423_fs05/cs423_fs05_lectures.htmlhttp://java.sun.com/docs/books/tutorial/networking/http://beej.us/guide/bgnet/