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POQt5 slot being called multiple times from a single emit statement
 

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  1. POQt5 slot being called multiple times from a single emit statement
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    <p>I'm relatively new to Qt, but I have done a little searching around. I have a base class that handles UDP broadcasting, and does the connect statements in the constructor of the class like this:</p> <pre><code>NetworkConnection::NetworkConnection(QObject *parent) : QObject(parent) // Based on QObject , m_server_search( new QUdpSocket ) // Our UDP Broadcast socket , m_waiting_for_server( false ) , m_found_server( false ) { qDebug() &lt;&lt; "NetworkConnection::constructor"; connect( m_server_search, SIGNAL(readyRead()), this, SLOT(serverResponse()), Qt::UniqueConnection ); if ( m_server_search-&gt;bind( QHostAddress::AnyIPv4, (quint16)PORT_MULTICAST, QUdpSocket::ShareAddress ) ) { if ( m_server_search-&gt;joinMulticastGroup( QHostAddress( MULTICAST_GROUP ) ) ) { connect( this, SIGNAL(broadcast(NetworkMessage)), this, SLOT(broadcast_message(NetworkMessage)), Qt::UniqueConnection ); this-&gt;m_ping_timer = this-&gt;startTimer(2000); qDebug() &lt;&lt; "Ping timer id=" &lt;&lt; this-&gt;m_ping_timer; } else qDebug() &lt;&lt; "Couldn't start multicast listener"; } else qDebug() &lt;&lt; "Couldn't bind multicast to port" &lt;&lt; PORT_MULTICAST; } </code></pre> <p>I set up a signal/slot interface for broadcasting:</p> <pre><code>signals: void serverFound(); void serverNotFound(); void broadcast(NetworkMessage); private slots: void serverResponse(); void broadcast_message( NetworkMessage msg ); </code></pre> <p>And <code>broadcast_message</code> looks like this:</p> <pre><code>void NetworkConnection::broadcast_message( NetworkMessage msg ) { QByteArray raw = msg.toString(); qDebug() &lt;&lt; "NetworkConnection::broadcast_message&gt;" &lt;&lt; raw; if ( m_server_search-&gt;writeDatagram( raw.data(), raw.size(), QHostAddress(MULTICAST_GROUP), (quint16)PORT_MULTICAST ) &lt; 1 ) qDebug() &lt;&lt; "Failed broadcast last message"; } </code></pre> <p>My timer works well, and here is the code:</p> <pre><code>void NetworkConnection::timerEvent(QTimerEvent *event) { qDebug() &lt;&lt; "NetworkConnection::timerEvent with id" &lt;&lt; event-&gt;timerId() &lt;&lt; "(ping timer=" &lt;&lt; this-&gt;m_ping_timer &lt;&lt; ")"; if ( event-&gt;timerId() == this-&gt;m_ping_timer ) { qDebug() &lt;&lt; "NetworkConnection::pingForServer"; if ( m_waiting_for_server &amp;&amp; !m_found_server ) { qDebug() &lt;&lt; "Server not found!"; emit this-&gt;serverNotFound(); return; } if ( !m_found_server ) { qDebug() &lt;&lt; "Sending a ping to the server"; NetworkMessage msg( m_software_guid, get_microseconds(), QString("whoisaserver") ); emit this-&gt;broadcast( msg ); m_waiting_for_server = true; m_found_server = false; } } } </code></pre> <p>I only get the text "Sending a pint to the server" once, but my broadcast_message outputs it's <code>qDebug()</code> multiple times.</p> <p>I'm not explicitly using multiple threads, and as you can see I'm using Qt::UniqueConnection, which is apparently having no affect?</p> <p>SO why would the slot be called multiple times? I've even tried debugging it a little and just calling this->broadcast( ... ) without using emit, and it still gets called multiple times.</p> <p><strong>Edit:</strong> I just added a counter to the <code>broadcast_message</code> slot, and it gets called 340 times. Is there any significance to that?</p>
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    1. PTQuestion
    1. USOzBarry
    1. USOzBarry
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    1. CObroadcast() is equivalent to emit broadcast(), `emit` does nothing. Are you really sure broadcast_message is not called from anywhere else? How does serverResponse() look like?
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      1. POQt5 slot being called multiple times from a single emit statement
      1. USFrank Osterfeld
    2. COvoid QIODevice::readyRead() is emitted every time new data arrives. Data is not the same as one complete communication. So the signal may be emitted for every bit of information. Never used UDP Sockets in QT though ;)
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      1. POQt5 slot being called multiple times from a single emit statement
      1. USSebastian Lange
    3. COI am 100% sure I am not calling broadcast from anywhere else. @sebastian-lange that is only for reading and I am writing. I couldn't figure it out, so I did a rewrite and ironed everything out. Still not 100% sure what the issue was, but it's fixed in my new version.
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      1. POQt5 slot being called multiple times from a single emit statement
      1. USOzBarry
 

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