Create a socket at a specific port in Java

A socket is one end-point of a two-way communication link between two programs running on the network. Socket classes are used to represent the connection between a client program and a server program. Socket Programming, us basically client-server programming where a socket is used as a link between them. We need to import the ‘java.net package in our program which provides two classes namely Socket class and ServerSocket class. Socket Class implements the client-side of the connection and ServerSocket class implements the server-side of the connection.

Procedure:

In order to create a socket, the ‘java.net‘ package needs to be imported thereafter using the Socket and ServerSocket class, we create the object of that class.

1. The Server opens a ServerSocket on a well-known port and waits for input.2. Meanwhile, the Client opens a (client) Socket with the server’s hostname and this well-known port address.3. It sends a request message to the server to initialize a communication session.

At Server Side

At server side

 1 import java.net.Socket;
 2 ServerSocket mySsocket= new ServerSocket(portnumber);

At client side

 1 import java.net.Socket;
 2 Socket myCsocket= new Socket( address, portnumber);

Note: The Socket class takes the two parameters namely Address and the Port number. This ask the server side for the IP address, and then it opens a socket to that server on that specified port.

Server side

 1 package com.java;
 2 
 3 import java.net.ServerSocket;
 4 import java.net.Socket;
 5 
 6 public class Example {
 7 
 8     public static void main(String[] args) {
 9 
 10         try {
 11             ServerSocket mySsocket = new ServerSocket(80);
 12 
 13             System.out.println("Server started");
 14             System.out.println("Waiting for a client ...");
 15 
 16             Socket socket = mySsocket.accept();
 17             System.out.println("Client accepted through the port number: "
 18                     + mySsocket.getLocalPort());
 19         } catch (Exception e) {
 20             System.out.println("Exception : " + e.getMessage());
 21         }
 22     }
 23 }

In the above example, a ServerSocket instance created by passing a port number. A socket class accept() method called that allows client program to connect to the server. An operation on client request can be perform using socket object.

Output

 1 Server started
 2 Waiting for a client ...
 3 Client accepted through the port number: 80

Client with port

Client example

 1 package com.example;
 2 
 3 import java.net.Socket;
 4 
 5 public class Example {
 6 	
 7 	public static void main(String[] args) throws Exception {
 8 		  
 9 	   try {
 10 	      Socket myCsocket = new Socket("localhost", 80);
 11 	      System.out.println("Connected to Server");
 12 	   } catch (Exception e) {
 13 	      return;
 14 	   }
 15 	}
 16 }

In the above example, a Socket object is created by specifying a hostname and port where a server is running. A socket operation can be performed and send request to server using socket object.

Output