Networking

Networking is the process of connecting the devices into a group to share the resources or information by using a medium.

Terminology used in networking:

i)IP address-It is a numeric value which is used to uniquely identify a particular device in the network.It can be assigned in the following two ways:-
a)Statically
b)Dynamically

ii)Protocol-A protocol defines set of rules and regulations for data communication.There are following two basic protocols for data communication:
a)TCP
b)UDP

iii)Port no-It is an integer value  which is used to uniquely identify a process in a particular system.Range of port no given to a process is 0-65535.Among these,0-1023 are already reserved.
           e.g. 80-http,25-SMTP

iv)Socket-Socket is the abstraction of IP address,port and protocol,i.e. Socket is the combination of IP address,protocol,and port.Socket can also be defined in the following ways:

• It represents the end point of a connection.
• Socket is the combination of a process and buffer.
• Socket represents the logical representation of physical connection. 

Sockets supported by java

java supports the following two types of sockets-

i)TCP based sockets

ii)UDP based sockets

i)TCP Based Sockets:-There are two types of TCP sockets-

   a)Client-side Socket-An object of java.net.Socket represents TCP based client side socket.

   b)Server-side Socket-An object of java.net.ServerSocket represents TCP based server side socket.

Constructors of Socket class-

=> public Socket()

=> public Socket(String host address,int host port)

Commonly used methods of Socket-

=> public InputStream getInputStream()

=> public OutputStream getOutputStream()

=> public void Connect(String host address,int host port)

Constructor of ServerSocket-

=> public ServerSocket(int port)

Commonly used method of ServerSocket-

=> public Socket accept()

Steps involved in Server and Client Socket communication:-

1.0--> server program creates ServerSocket and then wait for client request to establish the connection.

2.0--> client program creates a client Socket and this client Socket connects with ServerSocket.

2.1--> client Socket connects with ServerSocket.

2.2--> A copy of client Socket is obtained from the ServerSocket at server side.

3.0--> client program obtain an OutputStream associated with the client Socket.

3.1--> data is written to the Socket and transmittedto the corresponding ServerSocket at the server side.

3.2--> server program obtains InputStream from the client Socket at server side to read the data. 

        java class for server program is as under:

package mypack;

import java.io.DataInputStream;

import java.io.InputStream;

import java.net.ServerSocket;

import java.net.Socket;

public class TcpServer {

public static void main(String arg[])

{

try

{

ServerSocket ss= new ServerSocket(1234);

System.out.println("server is started and waiting for client request");

Socket sk = ss.accept();

System.out.println("client is connected.");

InputStream in = sk.getInputStream();

DataInputStream din = new DataInputStream(in);

while(true)

{

String msg = din.readUTF();

if(msg.equals("stop"))

break;

System.out.println("msg");

}

}catch(Exception e){e.printStackTrace();}

}

}

                    java class for client program is:-

package mypack;

import java.io.BufferedReader;

import java.io.DataInputStream;

import java.io.DataOutputStream;

import java.io.InputStream;

import java.io.InputStreamReader;

import java.io.OutputStream;

import java.net.ServerSocket;

import java.net.Socket;

public class TCPClient {

public static void main(String arg[])

{

try

{

Socket sk = new Socket("localhost",1234);

OutputStream os = sk.getOutputStream();

DataOutputStream dout = new DataOutputStream(os);

BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

while(true)

{

String msg = br.readLine();

dout.writeUTF(msg);

if(msg.equals("stop"))

break;

}

}catch(Exception e){e.printStackTrace();}

}

}