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66 lines
1.5 KiB
Markdown
66 lines
1.5 KiB
Markdown
---
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title: "QTcpSocket"
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date: 2020-03-20T16:21:07-04:00
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draft: false
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tags: ["C++", "Qt"]
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---
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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.
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Here is some shared code for both examples
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```c++
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QTcpSocket *socket = new QTcpSocket(this);
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quint16 listenPort = 4444;
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int timeout = 1000; // Units: milliseconds
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QHostAddress destination("192.168.0.2");
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```
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## `waitForDisconnected`
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Let's say that we have a `QTcpScoket` pointer named `socket`.
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```c++
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socket->connectToHost(destination, listenPort);
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if (!socket->waitForConnected(timeout)) {
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qDebug("Connection Timed Out.");
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}
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```
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Notes:
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- `waitForConnected` is a blocking call
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- This does not account for the host lookup call.
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## `QTimer`
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This method requires a little more setup. Let's assume we have a class named `Test` that inherits `QObject`.
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```c++
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// ....
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socket->connectToHost(destination, listenPort);
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timeoutTimer = new QTimer(this);
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timeoutTimer->setInterval(timeout);
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timeoutTimer->setSingleShot(true);
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connect(timeoutTimer, &QTimer::timeout, this, &Test::timeout);
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timeoutTimer->start();
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// ....
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void Test::timeout(void) {
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qDebug("Connected Timed Out.");
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socket->disconnectFromHost();
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}
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```
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Notes:
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- This method acts asynchronously
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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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```c++
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timeoutTimer->stop();
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```
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