Client Server Program in java |Java TCP Client – Server Program | Socket

Client Server Program in java |Java TCP Client – Server Program | Client Server Program in java |Socket

What is TCP Socket ?

A socket is one endpoint of a two-way communication link between two programs running on the network
A socket is bound to a port number so that the TCP layer can identify the application that data is destined to be sent to

TCP socket Connection

To make a connection request, the client makes a connection request to the server on the server’s machine and port
The client identifies itself with a local port number (usually assigned by the system) during the connection
If everything goes well, the server accepts the connection Upon acceptance, the server gets a new socket bound to the local endpoint bound to the same port and remote endpoint bound to the address and port of the client
The original socket continues to listen for connection requests
On the client side, if the connection is accepted, a socket is successfully created and the client can use the socket to communicate with the server
The java.net package provides Server Socket and Socket classes to create server and client sockets

TCP Socket Connection in Figure

Server Side Program | Client Server Program in java

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package server;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Scanner;
/**
 *
 * @author Achyut
 */
public class Server {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) throws IOException {

        final int PORT = 1234;
        System.out.println("Server started.");
        System.out.println("Listening to client...");
        
        try (
            ServerSocket serverSocket = new ServerSocket(PORT);
            Socket clientSocket = serverSocket.accept();
            PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
            Scanner in = new Scanner(clientSocket.getInputStream());
        ) {
            while (true) {
                String input = in.nextLine();
                if (input.equalsIgnoreCase("exit")) break;
                System.out.println("Received from client: " + input);      
                double radius = Double.valueOf(input);
                double area = Math.PI* radius *radius ;
                out.println(area);
                
            }
        }
        System.out.println("Server stopped");
    }
    }

Client Side Program | Client Server Program in java

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package client;

import java.io.IOException;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.Scanner;
/**
 *
 * @author 5442
 */
public class Client {

   public static void main(String[] args) throws IOException {
        final String HOST = "127.0.0.1";
        final int PORT = 1234;
        
        System.out.println("Client started.");
        
        try (
            Socket socket = new Socket(HOST, PORT);
            PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
            Scanner in = new Scanner(socket.getInputStream());
            Scanner s = new Scanner(System.in);
        ) {
            while (true) {
                System.out.print("Input: ");
                String input = s.nextLine();
                out.println(input);
                if (input.equalsIgnoreCase("exit")) break;
                System.out.println("Echoed from server: " + in.nextLine());
            }
        }
    }
    
}