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PODoes QThread::sleep() require the event loop to be running?
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copied!<p>I have a simple client-server program written in Qt, where processes communicate using MPI. The basic design I'm trying to implement is the following:</p> <ol> <li><p>The first process (the "server") launches a GUI (derived from <code>QMainWindow</code>), which listens for messages from the clients (using repeat fire <code>QTimer</code>s and asynchronous MPI receive calls), updates the GUI depending on what messages it receives, and sends a reply to every message.</p></li> <li><p>Every other process (the "clients") runs in an infinite loop, and all they are intended to do is send a message to the server process, receive the reply, go to sleep for a while, then wake up and repeat. Every process instantiates a single object derived from <code>QThread</code>, and calls its <code>start()</code> method. The <code>run()</code> method of these classes all look like this:</p></li> </ol> <p>from foo.cpp:</p> <pre><code>void Foo::run() { while (true) { // Send message to the first process // Wait for a reply // Do uninteresting stuff with the reply sleep(3); // also tried QThread::sleep(3) } } </code></pre> <p>In the client's code, there is no call to <code>exec()</code> anywhere, so no event loop should start.</p> <p>The problem is that the clients never wake up from sleeping (if I surround the <code>sleep()</code> call with two writes to a log file, only the first one is executed, control never reaches the second). Is this because I didn't start the event loop? And if so, what is the simplest way to achieve the desired functionality?</p>

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