Implement Echo Server by using TCP Socket

Q. Write a Java program to implement echo server by using TCP Socket.

Ans.

Server side program:

import java.net.*; 
import java.io.*; 
public class tcpechoserver 
{ 
public static void main(String[] arg) throws IOException 
{ 
ServerSocket sock = null; 
BufferedReader fromClient = null; 
OutputStreamWriter toClient = null; 
Socket client = null; 
try 
{ 
 sock = new ServerSocket(4000);
System.out.println("Server Ready");
client = sock.accept(); System.out.println("Client Connected"); 
fromClient = new BufferedReader(new
InputStreamReader(client.getInputStream())); 
toClient = new OutputStreamWriter(client.getOutputStream()); 
String line; 
while (true) 
{ 
line = fromClient.readLine(); 
if ( (line == null) || line.equals("bye")) 
break; 
System.out.println ("Client [ " + line + " ]");
 toClient.write("Server [ "+ line +" ]\n");
 toClient.flush(); 
} 
fromClient.close();
 toClient.close();
 client.close(); 
sock.close(); 
System.out.println("Client Disconnected"); 
} 
catch (IOException ioe) 
{ 
System.err.println(ioe);
}
}
}

 

Client side program:

import java.net.*; 
import java.io.*; 
public class tcpechoclient 
{ 
public static void main(String[] args) throws IOException 
{ 
BufferedReader fromServer = null, fromUser = null; 
PrintWriter toServer = null; 
Socket sock = null; 
try 
{ 
if (args.length == 0) 
sock = new Socket(InetAddress.getLocalHost(),4000); 
else 
sock = new Socket(InetAddress.getByName(args[0]),4000); 
fromServer = new BufferedReader(new
InputStreamReader(sock.getInputStream())); 
fromUser = new BufferedReader(new InputStreamReader(System.in)); 
toServer = new PrintWriter(sock.getOutputStream(),true); 
String Usrmsg, Srvmsg; 
System.out.println("Type \"bye\" to quit"); 
while (true)
{ 
System.out.print("Enter msg to server : "); 
Usrmsg = fromUser.readLine(); 
if (Usrmsg==null || Usrmsg.equals("bye")) 
{ 
toServer.println("bye"); break; 
}
 else 
toServer.println(Usrmsg); 
Srvmsg = fromServer.readLine(); 
System.out.println(Srvmsg); 
} 
fromUser.close(); 
fromServer.close(); 
toServer.close(); 
sock.close(); 
} 
catch (IOException ioe) 
{ 
System.err.println(ioe); 
}
}
}

  

First execute server side program,

Output:

javac tcpechoserver.java (//enter)

java tcpechoserver (//enter)

Server Ready

Then execute client side program,

Output:

javac tcpechoclient.java (//enter) 

java tcpechoclient (//enter)

Type "bye" to quit

Enter msg to server

Hi

Server [Hi]

javac tcpechoserver.java (//enter)

java tcpechoserver (//enter)

Server Ready

Client Connected

Client [Hi]

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