running a client/server prog on a single system

Question

im wondering if there are two programs, one called server and the other called client and these two are illustrating a server and client respectively,

Answer 1

Yes, you can write such a program. There is a useful tutorial for this. In short, it all boils down to prepare a ServerSocket:

ServerSocket createSocket() {
    ServerSocket serverSocket;
    try {
        serverSocket = new ServerSocket(3000);
    } catch (IOException ex) {
        ex.printStackTrace(System.err);
        throw ex;
    }
    return serverSocket;
}

From the programmer's point of view, there is no difference between a server residing on a remote machine or on a local one.

You could try writing two different programs, one for the server and one for the client. This is the main for the client:

public static void main(String[] args) {
  try {
      TCPClient client = new TCPClient() {};
      client.run();
  } catch(IOException e) {
    System.err.println("Error in Client " + e.getMessage());
  }

And this for the server:

public static void main(String[] args) {
  try {
      TCPServer server = new TCPServer() {};
      server.run();
  } catch(IOException e) {
    System.err.println("Error in Server " + e.getMessage());
  }

Then run the server first and then the client in a different console.