Multi Client -server Program in Java

Previous implementation of TCP Echo Server allows only one client to connect at a time To allow multiple clients to connect, use threads for each client connection in the server
We can build chat connection in java between two client using thread and multi client

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

Server Side Program | Multi Client -server Program in Java

/*
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 * 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 5442
 */
public class ThreadServer {
  public static void main(String[] args) throws IOException {
        final int PORT = 4040;
        ServerSocket serverSocket = new ServerSocket(PORT);
        
        System.out.println("Server started...");
        System.out.println("Wating for clients...");
        
        while (true) {
            Socket clientSocket = serverSocket.accept();
            Thread t = new Thread() {
                public void run() {
                    try (
                        PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
                        Scanner in = new Scanner(clientSocket.getInputStream());
                    ) {
                        while (in.hasNextLine()) {
                            String input = in.nextLine();
                            if (input.equalsIgnoreCase("exit")) {
                                break;
                            }
                            System.out.println("Received radius from client: " + input);
                            
                            double radius = Double.valueOf(input);
                            double area = Math.PI* radius *radius ;
                            out.println(area);
                        }
                    } catch (IOException e) { }
                }
            };
            t.start();
        }
    }   
}

Server Side Program | Multi 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 ThreadClient {
    public static void main(String[] args) throws IOException {
        final String HOST = "127.0.0.1";
        final int PORT = 4040;
        
        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());
            }
        }
    }
 
}