c++ - Qt create a dialog that waits for a network event -

i writing client client/server application. clients supposed login using login window. if login successful, "waiting" window appears (this window contains label). on server side there barrier waits n clients logged in; when happens, message broadcasted, waiting window supposed close , new window appears every client.

the networking interface implemented me, using low-level functions, not functionality provided qt.

the actual waiting loop this:

char buffer[256]; while (strcmp(buffer, "proceed"))     read(sockfd, buffer, 256); 

the problem if start loop in main thread, application blocks, obvious reasons.

how can make loop run , not block application, , close dialog when ends?

later edit: did attempt use qthreads, but, reasons don't understand yet, application still crashes:

class waitloop : public qthread { public:     waitloop(networkhandler &network) : network(network) {} private :     networkhandler &network;     void run() {         this->network.waitforgamestart();     } }; 

in wait dialog constructor:

waitloop *waitloop = new waitloop(network); connect(waitloop, signal(finished()), this, slot(gamestartslot())); waitloop->start(); 

the application still crashes using approach.

the sanest way approach not using low-level functions, because aren't writing in c. use @ least qabstractsocket wrap sockfd. setsocketdescriptor method lets it.

your code becomes non-blocking , asynchronous:

class controller : public qobject {   q_object   qstatemachine m_sm;   qstate s_init{&m_sm}, s_proceeding{&m_sm};   qabstractsocket m_socket;   q_signal void proceed();   q_slot void ondata() {     auto data = m_socket.readall();     if (data.contains("proceed")) proceed();   } public:   controller(qobject * parent = 0) : qobject(parent) {     connect(&m_socket, &qiodevice::readyread, this, &controller::ondata);     s_init.addtransition(this, &controller::proceed, &s_proceeding);     m_sm.setinitialstate(&s_init);     m_sm.start();   }   bool setup(quintptr fd) {     return m_socket.setsocketdescriptor(fd);   } }; 

through use of state machine, it's easy add more states, react transitions (see qstate::onentry signal, etc.), , ensure behavior correct. fleshing out uml statechart forces think handling corner cases, etc. see this answer full example.