There can be many variations in the TCP program to make it “Application Specific”. One such application specific program is Reverse of a String. For each client input, the server will return the reversed string.

tcpserver.java

import java.io.*;
import java.net.*;
class tcpserver
{
    public static void main(String args[])throws Exception
    {
        System.out.println("Server started....n");
        try
        {
            ServerSocket welcome_socket=new ServerSocket(1234);
            while(true)
            {
                Socket listen_socket=welcome_socket.accept();
                BufferedReader server_input=new BufferedReader(new InputStreamReader(System.in));
                BufferedReader client_out=new BufferedReader(new InputStreamReader(listen_socket.getInputStream()));
                DataOutputStream server_out=new DataOutputStream(listen_socket.getOutputStream());
                String client_str,server_str;
                client_str=client_out.readLine();
                System.out.println("Client:"+client_str+'n');
                int strln=client_str.length();
                for(int i=strln-1;i>=0;i--)
                    server_str=server_input.readLine();
                server_out.writeBytes(server_str+'n');
            }
        }
        catch (Exception e)
        {
            System.out.println("Error:"+e.getMessage());
        }
    }
}

tcpclient.java

import java.io.*;
import java.net.*;
class tcpclient
{
    public static void main(String args[])throws Exception
    {
        System.out.println("Client started...");
        try
        {
            Socket client_socket=new Socket("localhost",1234);
            while(true)
            {
                BufferedReader client_input=new BufferedReader(new InputStreamReader(System.in));
                BufferedReader server_out=new BufferedReader(new InputStreamReader(client_socket.getInputStream()));
                DataOutputStream client_out=new DataOutputStream(client_socket.getOutputStream());
                String client_str,server_str;
                System.out.println("Enter string:");
                client_str=client_input.readLine();
                client_out.writeBytes(client_str+'n');
                server_str=server_out.readLine();
                System.out.println("Reversed String:"+server_str+'\n');
            }
        }
        catch(Exception e)
        {
            System.out.println("Error:"+e.getMessage());
        }
    }
}