仅在调试模式下工作

Question

I'm trying to create a program for a distributed system. At the moment I have a thread for listening to connections, and a thread for sending, and a thread for receiving.

I've reached a problem where the client will connect but only when using breakpoints. I can't figure out the problem at all!. I've tried to implement things to slow the program down however nothing is working.

If you guys could take a look i'd be greatly appreciative.

  public static void main(String[] args) { System.out.println("Server starting on port 5000"); RecievingConnection reciever = new RecievingConnection(5000,0); //Recieving Connection reciever.start(); SendingConnection sender = new SendingConnection(5001,1); //Sending Connection sender.start(); while(true){ while(reciever.ready==true){ System.out.println("In"); nodes first = new nodes(reciever.socket,0); System.out.println("Node created"); first.start(); System.out.println("Client connected on port: " + reciever.socket.getLocalAddress()); nodes second = new nodes(sender.socket,1); second.start(); reciever.ready=false; sender.ready=false; reciever.connectionComplete=true; sender.connectionComplete=true; } } } 

  public RecievingConnection(int port, int mode) { Serverport = port; connectionMode = mode; try{ server = new ServerSocket(port); server.setSoTimeout(100000); } catch(IOException ex) { System.out.println(ex); } } public void run(){ while(true){ if(ready == false){ try { socket = server.accept(); ready = true; System.out.println("Attempting to connect using port: " + Serverport); while(connectionComplete == false){ //wait } } catch (IOException ex) { System.out.println(ex); } } } } 

The sending thread is basically the same code. Any idea what the problem is? "Nodes" is the thread for each node.

Answer 1

Your problem is almost certainly at:

    while (connectionComplete == false) {
        //wait
    }

This will loop forever, the other thtreads will not get any cpu time at all. It also explains why it works in debug - it's because in debug if you stop at a breakpoint, any other threads will get time.

You should at least do:

    while (connectionComplete == false) {
        //wait
        Thread.sleep(0);
    }

and maybe use a number much greater than 0 . This will allow other thtreads a chance to run.

I am not suggesting that this will make your code work correctly but it should remove the current problem.

---

After that there's another tight loop that won't let any other thread time.

    while (true) {
        if (ready == false) {

Change that to:

    while (true) {
        if (ready == false) {
            // ...
        } else {
            // Here too.
            Thread.sleep(0);
        }

    }

Answer 2

I solved it by adding a sleep in the main thread. I presume this is because the main thread takes priority over child threads?

Answer 3

You can't just share variables between threads. Make them volatile, synchronize or use CAS types like AtomicBoolean.

Read about it.

https://docs.oracle.com/javase/tutorial/essential/concurrency/interfere.html

http://www.journaldev.com/1061/java-synchronization-and-thread-safety-tutorial-with-examples

https://docs.oracle.com/javase/tutorial/essential/concurrency/atomicvars.html

Besides class "nodes" is not described here and classes are expected to start with an upper case letter.