Hi, I have passed the last 48 hours trying to understand a problem I was having with sockets. I was driving crazy but I think I finally reached a conclusion. Let me summarize:
- Program A that sends data via sockets to localhost - Program B, built in Qt, receives data via QUdpSocket (I have also tried with QTcpSocket and the problem is the same). Program A sends constant size messages (76 bytes) each 60 ms. Program B receives the message and prints the latency between the current message and the last message. The result is the following: latency 19 latency 60 latency 60 latency 60 latency 51 latency 59 latency 80 latency 61 latency 60 latency 58 latency 50 latency 60 latency 59 latency 538 latency 0 latency 43 latency 58 latency 62 latency 79 latency 50 latency 50 latency 61 latency 61 latency 58 latency 60 latency 80 latency 31 latency 59 latency 1946 latency 0 latency 54 latency 61 latency 49 latency 59 latency 52 latency 60 latency 58 latency 60 latency 60 latency 60 latency 60 latency 60 latency 51 latency 533 latency 0 latency 16 latency 60 latency 60 latency 60 latency 50 latency 60 latency 61 latency 60 latency 59 From time to time, in a pretty much regular way, the message receiving stalls and the latency is printed as being around 500ms/1000ms/2000ms. Even the interval between stalls is pretty much regular, around 14 packets. Each packet is 76 bytes, which multiplied by 14 gives around 1024. I didn’t rest while I couldn’t who the fault was. So I did a C program that receives data on a socket from the same source to ensure that there was no stalls or latency. The result was NO STALLS. Then, I have done another program, this time built in Qt, to send data via QUdpSocket to the program B. The result was: STALLS again! My conclusion is that somewhere in the underlying Qt socket handling, there is a buffer, to be filled before readyRead is sent. Is anybody familiar with this problem and know how to work around it? Is this a setting that can be tweaked? This doesn’t seem normal or acceptable. Thx, Regards, Nuno Santos _______________________________________________ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
