Hello everyone. I'm new in Java so please forgive any obscene errors that I may make :) I'm developing a program in Java that among other things it should also handle clients that will connect to a server. The server has 3 threads running, and I have created them in the following way : DaemonForUI du; DaemonForPort da; DaemonForCheck dc; da = new DaemonForPort(3); dc = new DaemonForCheck(5); du = new DaemonForUI(7); Thread t_port = new Thread(da); Thread t_check = new Thread(dc); Thread t_ui = new Thread(du); t_port.setName("v1.9--PORTd"); t_check.setName("v1.9-CHECKd"); t_ui.setName("v1.9----UId"); t_port.start(); t_check.start(); t_ui.start(); Each thread handles a different aspect of the complete program. The thread t_ui is responsible to accept asynchronous incoming connections from clients, process the sent data and send other data back to the client. When I remove all the commands from the previous piece of code that has to with the t_ui thread, everything runs ok which in my case means that the other threads are printing their debug messages. If I set the t_ui thread to run too, then the whole program blocks at the "accept" of the t_ui thread. After reading at online manuals I saw that the accepted connections should be non-blocking, therefore use something like that : public ServerSocketChannel ssc = null; ssc = ServerSocketChannel.open(); ssc.socket().bind(new InetSocketAddress(port)); ssc.configureBlocking(false); SocketChannel sc = ssc.accept(); if (sc == null) { ; } else { System.out.println("The server and client are connected!"); System.out.println("Incoming connection from: " + sc.socket().getRemoteSocketAddress()); in = new DataInputStream(new BufferedInputStream(sc.socket().getInputStream())); out = new DataOutputStream(new BufferedOutputStream(sc.socket().getOutputStream())); //other magic things take place after that point... The thread for t_ui is created as follows : class DaemonForUI implements Runnable{ private int cnt; private int rr; public ListenerForUI serverListener; public DaemonForUI(int rr){ cnt = 0; this.rr = rr; serverListener = new ListenerForUI(); } public static String getCurrentTime() { final String DATE_FORMAT_NOW = "yyyy-MM-dd HH:mm:ss"; Calendar cal = Calendar.getInstance(); SimpleDateFormat sdf = new SimpleDateFormat(DATE_FORMAT_NOW); return (sdf.format(cal.getTime())); } public void run() { while(true) { System.out.println(Thread.currentThread().getName() + "\t (" + cnt + ")\t (every " + rr + " sec) @ " + getCurrentTime()); try{ Thread.sleep(rr * 1000); cnt++; } catch (InterruptedException e){ e.printStackTrace(); } } } } Obviously, I'm doing something wrong at the creation of the socket or at the use of the thread. Do you know what is causing the problem? Every help would be greatly appreciated.