Socket Programming using TCP Socket

Socket:

Sockets allow communication between two different processes on the same or different machines. A Unix Socket is used in a client-server application framework. A server is a process that performs some functions on request from a client. The client in socket programming must know two information:

• IP Address of Server, and
• Port number.

Server Side Programming in Java:

Method		Description
1) public Socket accept()	returns the socket and establish a connection between server and client.
2) public synchronized void close()	closes the server socket.

Java Program for server side:

import java.net.*;

import java.io.*;

  

public class Server

{

    //initialize socket and input stream

    private Socket          socket   = null;

    private ServerSocket    server   = null;

    private DataInputStream in       =  null;

  

    // constructor with port

    public Server(int port)

    {

        // starts server and waits for a connection

        try

        {

            server = new ServerSocket(port);

            System.out.println("Server started");

  

            System.out.println("Waiting for a client ...");

  

            socket = server.accept();

            System.out.println("Client accepted");

  

            // takes input from the client socket

            in = new DataInputStream(

                new BufferedInputStream(socket.getInputStream()));

  

            String line = "";

  

            // reads message from client until "Over" is sent

            while (!line.equals("Over"))

            {

                try

                {

                    line = in.readUTF();

                    System.out.println(line);

  

                }

                catch(IOException i)

                {

                    System.out.println(i);

                }

            }

            System.out.println("Closing connection");

  

            // close connection

            socket.close();

            in.close();

        }

        catch(IOException i)

        {

            System.out.println(i);

        }

    }

  

    public static void main(String args[])

    {

        Server server = new Server(5000);

    }

}

Client side programming in Java:

Method	Description
1) public InputStream getInputStream()	returns the InputStream attached with this socket.
2) public OutputStream getOutputStream()	returns the OutputStream attached with this socket.
3) public synchronized void close()	closes this socket

Java Program for client side:

import java.net.*;

import java.io.*;

  

public class Client

{

    // initialize socket and input output streams

    private Socket socket            = null;

    private DataInputStream  input   = null;

    private DataOutputStream out     = null;

  

    // constructor to put ip address and port

    public Client(String address, int port)

    {

        // establish a connection

        try

        {

            socket = new Socket(address, port);

            System.out.println("Connected");

  

            // takes input from terminal

            input  = new DataInputStream(System.in);

  

            // sends output to the socket

            out    = new DataOutputStream(socket.getOutputStream());

        }

        catch(UnknownHostException u)

        {

            System.out.println(u);

        }

        catch(IOException i)

        {

            System.out.println(i);

        }

  

        // string to read message from input

        String line = "";

  

        // keep reading until "Over" is input

        while (!line.equals("Over"))

        {

            try

            {

                line = input.readLine();

                out.writeUTF(line);

            }

            catch(IOException i)

            {

                System.out.println(i);

            }

        }

  

        // close the connection

        try

        {

            input.close();

            out.close();

            socket.close();

        }

        catch(IOException i)

        {

            System.out.println(i);

        }

    }

  

    public static void main(String args[])

    {

        Client client = new Client("127.0.0.1", 5000);

    }

}

Snapshots:

                   Client                                                                            Server