GreetingClient.java

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

public class GreetingClient
{
   public static void main(String [] args)
   {
      String serverName = args[0];
      int port = Integer.parseInt(args[1]);
      try
      {
         System.out.println("Connecting to " + serverName +
		 " on port " + port);
         Socket client = new Socket(serverName, port);
         System.out.println("Just connected to " 
		 + client.getRemoteSocketAddress());
         OutputStream outToServer = client.getOutputStream();
         DataOutputStream out = new DataOutputStream(outToServer);
         out.writeUTF("Hello from "
                      + client.getLocalSocketAddress());
         InputStream inFromServer = client.getInputStream();
         DataInputStream in =
                        new DataInputStream(inFromServer);
         System.out.println("Server says " + in.readUTF());
         client.close();
      }catch(IOException e)
      {
         e.printStackTrace();
      }
   }
}

GreetingServer.java

import java.io.*;
import java.net.*;
import java.util.Scanner;

class GreetingServer{
	private static GreetingServer server;
	static int Port = 3535;
	static ServerSocket Socket;
	
	public GreetingServer(){
		try{
			Socket = new ServerSocket(setSocket());
		}catch(Exception e){
			System.out.println("Error: "+e.getMessage());
		}
	}
	
	private int setSocket(){
		Scanner in = new Scanner(System.in);
		System.out.print("Enter socket number:");
		Port = in.nextInt();
		System.out.println("Socket number "+Port+" created.");
		System.out.println("Listening...");
		return Port;
	}
	
	public static void main(String argv[]) throws Exception {
		server = new GreetingServer();
		String clientSentence;          
		String capitalizedSentence;          
		while(true){             
			Socket connectionSocket = Socket.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() + " from "+Port+'\n';             
			outToClient.writeBytes(capitalizedSentence);          
		}       
	}
}