Simple Date client/server example. Start the server, and then running the client gets the date from the server and prints it.

DateClient.java

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

public class DateClient {
  public static final int portNumber = 6013;

  public static void main(String[] args) throws IOException {
    String server;
    // Use "127.0.0.1", i.e., localhost, if no server is specified.
    if (args.length == 0) {
      server = "127.0.0.1";
    } else {
      server = args[0];
    }

    try {
      // Connect to the server
      Socket socket = new Socket(server, portNumber);

      // Get the input stream so we can read from that socket
      InputStream input = socket.getInputStream();
      BufferedReader reader = new BufferedReader(new InputStreamReader(input));

      // Print all the input we receive from the server
      String line;
      while ((line = reader.readLine()) != null) {
        System.out.println(line);
      }

      // Close the socket when we're done reading from it
      socket.close();

    // Provide some minimal error handling.
    } catch (ConnectException ce) {
      System.out.println("We were unable to connect to " + server);
      System.out.println("You should make sure the server is running.");
    } catch (IOException ioe) {
      System.out.println("We caught an unexpected exception");
      System.err.println(ioe);
    }
  }
}

DateServer.java

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

public class DateServer {
  public static final int portNumber = 6013;

  public static void main(String[] args) {
    try {
      // Start listening on the specified port
      ServerSocket sock = new ServerSocket(portNumber);

      // Run forever, which is common for server style services
      while (true) {
        // Wait until someone connects, thereby requesting a date
        Socket client = sock.accept();
        System.out.println("Got a request!");

        // Construct a writer so we can write to the socket, thereby
        // sending something back to the client.
        PrintWriter writer = new PrintWriter(client.getOutputStream(), true);

        // Send the current date back tothe client.
        writer.println(new java.util.Date().toString());

        // Close the client socket since we're done.
        client.close();
      }
    // *Very* minimal error handling.
    } catch (IOException ioe) {
      System.out.println("We caught an unexpected exception");
      System.err.println(ioe);
    }
  }
}