Brandon Rozek

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PhD Student @ RPI studying Automated Reasoning in AI and Linux Enthusiast.


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There are two ways that I can think of for checking if a TCP socket times out in Qt. You can either use waitForConnected or a QTimer. The Qt 5.14 documentation noted that the waitForConnected call may randomly fail in Windows.

Here is some shared code for both examples

QTcpSocket *socket = new QTcpSocket(this);
quint16 listenPort = 4444;
int timeout = 1000; // Units: milliseconds
QHostAddress destination("");


Let’s say that we have a QTcpScoket pointer named socket.

socket->connectToHost(destination, listenPort);
if (!socket->waitForConnected(timeout)) {
    qDebug("Connection Timed Out.");


  • waitForConnected is a blocking call
  • This does not account for the host lookup call.


This method requires a little more setup. Let’s assume we have a class named Test that inherits QObject.

// ....
socket->connectToHost(destination, listenPort);
timeoutTimer = new QTimer(this);
connect(timeoutTimer, &QTimer::timeout, this, &Test::timeout);
// ....

void Test::timeout(void) {
    qDebug("Connected Timed Out.");


  • This method acts asynchronously

In order for the the timeout function to not always hit, we need to make sure we stop the timer when data is received or a TCP error occurs

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