TCP Server - Client

Client

import java.io.*;
import java.net.*;

class TCPClient
 {
  public static void main(String argv[]) throws Exception
  {
   String sentence;
   String modifiedSentence;
   BufferedReader inFromUser = new BufferedReader( new InputStreamReader(System.in));
   Socket clientSocket = new Socket("localhost", 6789);
   DataOutputStream outToServer = new DataOutputStream(clientSocket.getOutputStream());
   BufferedReader inFromServer = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
   sentence = inFromUser.readLine();
   outToServer.writeBytes(sentence + '\n');
   modifiedSentence = inFromServer.readLine();
   System.out.println("FROM SERVER: " + modifiedSentence);
   clientSocket.close();
  }
 }



Server

import java.io.*;
 import java.net.*;

class TCPServer
 {
    public static void main(String argv[]) throws Exception
       {
          String clientSentence;
          String capitalizedSentence;
          ServerSocket welcomeSocket = new ServerSocket(6789);

         while(true)
          {
             Socket connectionSocket = welcomeSocket.accept();
             BufferedReader inFromClient =
                new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
             DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream());
             clientSentence = inFromClient.readLine();
             System.out.println("Received: " + clientSentence);
             capitalizedSentence = clientSentence.toUpperCase() + '\n';
             outToClient.writeBytes(capitalizedSentence);
          }
       }
 }