[Live-devel] RTSP Server Packet Loss

[Martin Sherburn]

Dear Live555 Developers,

I have discovered a bug whereby UDP packets are getting lost using live555MediaServer. The issue is that the socket used for sending the packets is set to non-blocking mode. Occasionally when the application sends a lot of data in a short amount of time the sendto function within writeSocket in GroupsockHelper.cpp  returns -1, and WSAGetLastError reports WSAEWOULDBLOCK. Unfortunately the packet is then discarded and no attempts to try and send it again later are made.

I was able to fix this by putting the socket into blocking mode, thus if the buffers are full it will wait until there is space before returning which should be a very short amount of time anyway. I have tested the fix under both windows and linux and in both cases it reduced my packet loss to 0 measured on the client side. I have attached a patch, please let me know if there could be any reason it's not a good idea to make the sending socket blocking. The alternative would be to keep the socket in non-blocking mode but make sure that the packet is re-queued for sending upon receiving the WSAEWOULDBLOCK error, that seems like a more involved change though.

Regards,

Martin Sherburn.

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