tcp.java

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

class tcp {
 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);
  }
 }
}