Thread: TCP Listening in C++
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Unread 12-28-2012, 11:53 AM
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Re: TCP Listening in C++ -- BUG in WPILib
We used UDP on the 'bot last season for communicating from Arduinos to the cRIO. The one thing that we found is that the WPILib has issues with unread UDP packets. Evidently, the WPILib is always monitoring and hooking UDP traffic (it may do something similar with TCP traffic) so that rather than dropping a packet on the floor as it should, WPILib tries to buffer everything. I can see why they want to do this (in case things start to fall behind, you don't want important control packets dropped), but it's against what UDP was built to do. Nonetheless, if you don't service the UDP packets (say, it's a periodic transmission from your RPM sensor), they eventually cause the whole robot to lock up when the internal WPILib buffers overflow. This is clearly a bug in WPILib. However, you can get around it by always reading the UDP socket and tossing the packet away in your teleop disabled routine.

Good Luck,

Mike
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