[Qt-interest] Major bug in QAbstractSocket's method waitForReadyRead()

[Patric]

Hello, please take a look at this. 
I have a class here. It's called SNMP session and it sends some simple get and set requests. It uses QUdpSocket and have few other fields : 

QUdpSocket udpSocket;
QHostAddress *agentAddress;

qint16 agentPort;

qint16 socketPort;



Here is the constructor : 



SNMPSession::SNMPSession(const QString &agentAddress, qint16 agentPort, qint16 socketPort)

: QObject()

{

this->agentAddress = new QHostAddress(agentAddress);

this->agentPort = agentPort;

this->socketPort = socketPort;

udpSocket.bind(socketPort);

}



Nothing sophisticated. Here I have some test code which shows the bug I'm talking about : 



SNMPSession session("192.168.0.100", 161, 162);

int error;

error = session.sendSetRequest("private", "1.3.6.1.4.1.32324.1.4.4.1.0", "test");

error = session.sendSetRequest("private", "1.3.6.1.4.1.32324.1.4.4.1.0", "test");

error = session.sendSetRequest("private", "1.3.6.1.4.1.32324.1.4.4.1.0", "test");

error = session.sendSetRequest("private", "1.3.6.1.4.1.32324.1.4.4.1.0", "test");

error = session.sendSetRequest("private", "1.3.6.1.4.1.32324.1.4.4.1.0", "test");

error = session.sendSetRequest("private", "1.3.6.1.4.1.32324.1.4.4.1.0", "test");

error = session.sendSetRequest("private", "1.3.6.1.4.1.32324.1.4.4.1.0", "test");

error = session.sendSetRequest("private", "1.3.6.1.4.1.32324.1.4.4.1.0", "test");

error = session.sendSetRequest("private", "1.3.6.1.4.1.32324.1.4.4.1.0", "test");

error = session.sendSetRequest("private", "1.3.6.1.4.1.32324.1.4.4.1.0", "test");



In my methods (sendSetRequest and sendGetRequest) I have the following line : 



 if(udpSocket.waitForReadyRead(5000))

{

receivedDatagram.resize(udpSocket.pendingDatagramSize());

udpSocket.readDatagram(receivedDatagram.data(), receivedDatagram.size());

return receivedDatagram.at(errorIndex);

}





I have a sniffer program, more specifically Wireshark. There I can see my requests and my responses. The problem is, that according to that code up there it should wait 5 seconds for the new package. But there are situations when it don't wait, it just returns false. I'm talking for the waitForReadyRead method. So here are the situations : 



1. My network cable is plugged in. The first setRequest is successful, so it returns true. After that I'm removing the cable. The second request is unsuccessful, so it waits 5 seconds. And all other requests wait for five seconds. And this is the correct behaviour. 



2. My cable IS NOT plugged. The first setRequest is unsuccessful, so it waits 5 seconds and continues with the second. But here ! it don't wait 5 seconds, it immediately returns FALSE. Which I think is not correct. 







Please, correct me if I'm wrong. I also have some deadline here and this was very very bad surprise... 



Best regards, 

Patric



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