Help with startup

[Adriano Ferreira]

Hello, I wonder if I can make my application run only once, even when it is initialized by the startup of windows. I need that because if my server suddenly shut down the application starts automatically with your computer, and it is possible that it did not open again at startup of windows if another person to log on the server.
I tried with lock a port but it did not runs, I'm trying now use the class Socket for it, check it

 public class AppLock

{
    private int port;
      Socket socket;

public AppLock(int lockport) {

   port = lockport;
}

public void lock() throws IOException
{
                socket = new Socket("127.0.0.1", 7000);
        
       
}

    public void unlock() {

    try
    {
        socket.close();
    }

    catch (IOException ioex)
    {
            ioex.getMessage();
    }
}


    public boolean isLocked()
    {
        boolean retorno = false;
        try {
                socket = new Socket("127.0.0.1", 7800);
                //tenta dar unlock na porta
                socket.close();

                }

        catch (IOException ioex) {
            retorno = true;
            System.out.println(ioex.getMessage());
        }

        return retorno;
    }

}

eu nao consigo abrir a minha aplicacao porque sempre ocorre o seguinte erro:
Connection refused: connect
Estou no aguardo

[Jesper de Jong]

Welcome to JavaRanch.

One way to check if a copy of your program is already running is indeed by opening a socket, but you should use ServerSocket for that, not a regular Socket.

What you should do is create a ServerSocket and make it listen on a specific port (for example 7000 or 7800, or whatever number you want to use) by calling accept() on the ServerSocket. If there is another process already listening on that port, you will get an error (something like "port already in use"), which indicates that there is probably already another copy of your program running on the server.

[Adriano Ferreira]

Jesper de Jong wrote:Welcome to JavaRanch.

One way to check if a copy of your program is already running is indeed by opening a socket, but you should use ServerSocket for that, not a regular Socket.

What you should do is create a ServerSocket and make it listen on a specific port (for example 7000 or 7800, or whatever number you want to use) by calling accept() on the ServerSocket. If there is another process already listening on that port, you will get an error (something like "port already in use"), which indicates that there is probably already another copy of your program running on the server.

Thank you very much for the answer
I will try it

[Adriano Ferreira]

Adriano Ferreira wrote:

Jesper de Jong wrote:Welcome to JavaRanch.

One way to check if a copy of your program is already running is indeed by opening a socket, but you should use ServerSocket for that, not a regular Socket.

What you should do is create a ServerSocket and make it listen on a specific port (for example 7000 or 7800, or whatever number you want to use) by calling accept() on the ServerSocket. If there is another process already listening on that port, you will get an error (something like "port already in use"), which indicates that there is probably already another copy of your program running on the server.

Thank you very much for the answer
I will try it

Thanks for having me on the forum, I would like to thank you for the tip, I managed to do what I wanted, thank you
Here's the code of the class:

import java.io.IOException;
import java.net.ServerSocket;

/**
 *
 * @author abalbino
 */

public class Porta
{
    int port ;
    ServerSocket serverSocket ;
// ------------------------------------------------------------------
    public Porta(int lockport)
    {
        port = lockport;
    }

//  ------------------------------------------------------------------
    public void lock() throws IOException {
        serverSocket = new ServerSocket(port);
        serverSocket.accept();
    }

//  ------------------------------------------------------------------
    public void unlock() {
        try {
            serverSocket.close();
        } catch (IOException ioex) {
        }
    }

//  ------------------------------------------------------------------
    public static boolean isLocked(int lockport) {
        boolean locked = false;
        try {
            ServerSocket ss = new ServerSocket(lockport);
            //abaixo tenta dar unlock na porta
            ss.close();
        } catch (IOException ioex) {
            locked = true;
        }
        return locked;
    }

}

[Jesper de Jong]

Thanks for posting back your solution! That might be helpful if someone later has a similar problem.