Multi-Threaded Echo Server in Java

Implement a Multi-threading application for echo server using socket programming in JAVA.

Implementation

Server Side

1. Create a Server Class implementing the Runnable interface
2. In the run method, create a data input and output stream with a client.
3. In the main method write code to create a ServerSocket at a give port.
4. Create a infinite loop, to accept server connection from clients and launch a thread.
5. In the thread, when we catch an IOException we use return to quit. IOException occurs when the pipe is broken, that is, the client leaves.
6. Additionally we have give id's to identify when a client joined and left.

Client Side

1. Establish connection with server
2. Create Input and output streams for interacting with the server
3. Create a infinite loop to send messages to echo server
4. Quit the loop on get quit as an input.

Server Side Code

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.PrintStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Scanner;


public class Server implements Runnable{
 int id;
 Socket csocket;
 Server(Socket csocket, int id) {
    this.id=id;
       this.csocket = csocket;
    }
 
 
 public void run() {
  System.out.println("Client with Id= " + id + " connected");
  DataInputStream input=null;
     try {
        input = new DataInputStream(csocket.getInputStream());
     }
     catch (IOException e) {
        System.out.println(e);
     }
     
     
     DataOutputStream output=null;
     try {
        output = new DataOutputStream(csocket.getOutputStream());
     }
     catch (IOException e) {
        System.out.println(e);
     }
     
     while(true){
      try {
    output.writeUTF(input.readUTF());
   } catch (IOException e) {
    System.out.println("Client with Id= " + id + " exited");
    return;
    // TODO Auto-generated catch block
    
   }
     }
    }

 public static void main(String[] args) {
  int id=1;
  Scanner sc=new Scanner(System.in);
  int pno;
  // TODO Auto-generated method stub
  System.out.println("This is the Server Program");
  System.out.println("Enter the port number");
  pno=sc.nextInt();
  
  System.out.println("Attempting to create the server socket");
  ServerSocket MyService=null;
  try {
   MyService = new ServerSocket(pno);
   System.out.println("Server Socket Created Successfully");
  }
  catch (IOException e) {
   System.out.println(e);
  }
  System.out.println("Waiting for client");
  
       while (true) {
          Socket sock=null;
   try {
    sock = MyService.accept();
   } catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }
          System.out.println("Connected to a new Client");
          new Thread(new Server(sock,id++)).start();
       }
     
    
 }

}

Client Side Code

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.PrintStream;
import java.net.Socket;
import java.util.*;

public class Client {

 public static void main(String[] args) {
  Scanner sc=new Scanner(System.in);
  String sip;
  int pno;
  // TODO Auto-generated method stub
  System.out.println("This is the Client Program");
  System.out.println("Enter the Server ip");
  sip=sc.nextLine();
  System.out.println("Enter the Port Number to Use");
  pno=sc.nextInt();
  System.out.println("Attempting to create the Socket");
  Socket MyClient=null;
     try {
            MyClient = new Socket(sip, pno);
            System.out.println("Socket Created Successfully");
     }
     catch (IOException e) {
         System.out.println(e);
     }
     System.out.println("Attempting to create input Stream");
     DataInputStream input=null;
     try {
        input = new DataInputStream(MyClient.getInputStream());
        System.out.println("Input Stream Created Successfully");
     }
     catch (IOException e) {
        System.out.println(e);
     }
     
     System.out.println("Attempting to create Ouput Stream");
     DataOutputStream output=null;
  try {
   output = new DataOutputStream(MyClient.getOutputStream());
  } catch (IOException e1) {
   // TODO Auto-generated catch block
   e1.printStackTrace();
  }
     System.out.println("Output Stream created successfully");
     
     System.out.println("Connected to Echo Server");
     System.out.println("Enter the text which you want to be echoed back");
     System.out.println("Type quit to exit");
     while(true){
      String strIn=sc.nextLine();
      String copy=new String(strIn);
      if (copy.trim().equals("quit")){ 
       System.out.println("Detected quit.\nTerminating Program");
       break;
       
      }
      try {
    output.writeUTF(strIn);
   } catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }
      try {
    System.out.println(input.readUTF());
   } catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }
      
     }
     
     try {
        output.close();
        input.close();
        MyClient.close();
     } 
     catch (IOException e) {
        System.out.println(e);
     }
     
     
 }

}

Server Side Output

[student@localhost bin]$ java Server

This is the Server Program

Enter the port number

7562

Attempting to create the server socket

Server Socket Created Successfully

Waiting for client

Connected to a new Client

Client with Id= 1 connected

Client with Id= 1 exited

Connected to a new Client

Client with Id= 2 connected

Client with Id= 2 exited

Client Side Output

[pict@localhost bin]$ java Client

This is the Client Program

Enter the Server ip

127.0.0.1

Enter the Port Number to Use

7562

Attempting to create the Socket

Socket Created Successfully

Attempting to create input Stream

Input Stream Created Successfully

Attempting to create Ouput Stream

Output Stream created successfully

Connected to Echo Server

Enter the text which you want to be echoed back

Type quit to exit

test

test

go

go

quit

Detected quit.

Terminating Program

[student@localhost bin]$ java Client

This is the Client Program

Enter the Server ip

7562

Enter the Port Number to Use

^C

[student@localhost bin]$ java Client

This is the Client Program

Enter the Server ip

127.0.0.1

Enter the Port Number to Use

7562

Attempting to create the Socket

Socket Created Successfully

Attempting to create input Stream

Input Stream Created Successfully

Attempting to create Ouput Stream

Output Stream created successfully

Connected to Echo Server

Enter the text which you want to be echoed back

Type quit to exit

connected

connected

quit

Detected quit.

Terminating Program