run server socket code in background and then run client code

Question

After merging the code from two files (client and server) into into one, the control never reaches the client code anymore. However, I need to run server code in background and then run my client code.

Here is my code:

 //Server code 

 try {
        ServerSocket serverSocket = null; 

    try { 
         serverSocket = new ServerSocket(10007); 
        } 
    catch (IOException e) 
        { 
         System.err.println("Could not listen on port: 10007."); 
         System.exit(1); 
        } 

    Socket clientSocket = null; 
    System.out.println ("Waiting for connection.....");

    try { 
         clientSocket = serverSocket.accept(); 
        } 
    catch (IOException e) 
        { 
         System.err.println("Accept failed."); 
         System.exit(1); 
        } 

    System.out.println ("Connection successful");
    System.out.println ("Waiting for input.....");

    PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), 
                                      true); 
    BufferedReader in = new BufferedReader( 
            new InputStreamReader( clientSocket.getInputStream())); 

    String inputLine; 

    while ((inputLine = in.readLine()) != null) 
        { 
         System.out.println ("Server: " + inputLine); 
         out.println(inputLine); 

         if (inputLine.equals("Bye.")) 
             break; 
        } 

    out.close(); 
    in.close(); 
    clientSocket.close(); 
    serverSocket.close(); 

  //Client code 
        String serverHostname = new String ("127.0.0.1");
        System.out.println ("Attemping to connect to host " +
                serverHostname + " on port 10007.");
        Socket echoSocket = null;
        try {
            echoSocket = new Socket(serverHostname, 10007);
            out = new PrintWriter(echoSocket.getOutputStream(), true);
            in = new BufferedReader(new InputStreamReader(
                                        echoSocket.getInputStream()));
        } catch (UnknownHostException e) {
            System.err.println("Don't know about host: " + serverHostname);               
        } catch (IOException e) {
            System.err.println("Couldn't get I/O for "
                               + "the connection to: " + serverHostname);              
        }

        BufferedReader stdIn = new BufferedReader(
                                   new InputStreamReader(System.in));
        String userInput;

        System.out.print ("input: ");           
            while ((userInput = stdIn.readLine()) != null) {
                out.println(userInput);
                System.out.println("echo: " + in.readLine());
                System.out.print ("input: ");
            }
        out.close();
        try {
            in.close();           
            stdIn.close();           
            echoSocket.close();
        } catch (IOException ex) {
            Exceptions.printStackTrace(ex);
        }

I don't understand how to run my server code in background and then run my client code.

See this working [example](http://stackoverflow.com/a/3245805/230513). — trashgod, Nov 08 '12 at 19:12
Check out the [Concurrency](http://docs.oracle.com/javase/tutorial/essential/concurrency/) tutorial — MadProgrammer, Nov 08 '12 at 19:14

Frank · Answer 1 · 2012-11-08T19:41:24.693

0

You need to make 2 classes:

One Client
One Server

Each one will have it's own main() method.

Like this you can start 2 JVM's one server, one Client

Or in one Class:

Create 2 static inner classes the implement Runnable and you start both from inside your main class: (i take the assumption here that your main class is called Starter)

public static main(String args [ ]) {
                new Thread(new Starter.Server()).start();
                new Thread(new Starter.Client()).start();
            }

I will let you do the cleanup code...

edited Nov 08 '12 at 19:41

answered Nov 08 '12 at 19:15

Frank

16,476
7
38
51

But i need to run both in one class on one click. Is it Possible? – Sandip Armal Patil Nov 08 '12 at 19:23
Yes, but then you will have to spawn a thread, you have 2 options... the old way, then you look at the runnable interface, or the new way then you look at the Concurrency framework. – Frank Nov 08 '12 at 19:37
@Frank How is Runnable "old" and the concurrency framework "new"? Runnable, as far as I'm aware, is a part if the concurrency framework – MadProgrammer Nov 08 '12 at 20:10
@SandipArmalPatil can you elaborate on why it need to run in "one" class? – MadProgrammer Nov 08 '12 at 20:11
Runnable has been around for a while since JDK 1.0... there are other way's now – Frank Nov 08 '12 at 20:14
@MadProgrammer: i accept ip and port from user in textfields and when i click on run button it should show me output. Therefore i am trying to run it in one class! – Sandip Armal Patil Nov 09 '12 at 05:07
@SandipArmalPatil The problem is the socket comms are blocking, so while you're reading/writing to/from the client, you can't connect to the server. They should be separate concepts/classes. They may need a controller to get the two to work together though – MadProgrammer Nov 09 '12 at 05:32

score 0 · Answer 2 · answered Nov 08 '12 at 19:22

Use a public static class Client nested inside the main Server class. Each of them can have its own main method, so this is a way to achieve your goal of everything in one file, yet two separate entry points.

Another choice would be to have a single entry point but make it start two threads, one for the client and one for the server.

score 0 · Answer 3 · answered Nov 08 '12 at 23:11

Technically you could do this all in one source file by instantiating a thread that invokes the server code like this

    // Start the Server
    new Thread(new Runnable() {
        public void run() {
            // .. all the server code
        }
    }).start();

    // Start the client

    // .. all the client code

Behind the scenes, Java is probably creating anonymous inner classes for things like the new Runnable() { } technique.

run server socket code in background and then run client code

3 Answers3