I want to create a UDP listener that is non-blocking.
To do so I use SysSockSelect function. The problem is that the value diReady (Number of sockets that are ready for IO) never becomes 1.
The code I have is:

tvTimeout.tv_sec:= 0;
tvTimeout.tv_usec:= 0;
fdRead.fd_count:= 1;
fdRead.fd_array[0]:= hListenSocket;
Socket_Result := NBS.SysSockSelect(NBS.SOCKET_FD_SETSIZE, ADR(fdRead), 0, 0, ADR(tvTimeout), ADR(diReady));

I am sure data is ready for IO because when I call the function SysSockRecv data is read.

The same code I use in CoDeSys v2.3 and there it works.

Does anyone know why this doesn't work in v3.5 SP10?

Thanks,
Richard

Hi Richard,

I would recommend to use this project from that forum post based on netbase services:
l viewtopic.php?f=21&t=6625&hilit=UDP+raspberry#p13743 l

BR
Edwin

Hi Edwin,

Function block UDP_Receive is also blocking.
But I have used UDP_Receive in a separate task so now it doesn't matter that is it blocking.

Thanks,
Richard

Hi, sorry for budding in.
Have you tried to program the blocking sockets in a different program with a different task yet?
If you build your communication in a different task, your main program does not get hindered by blocking communication.
Another way is to implement communication via asynchronous jobs with a callback.
Try searching the CODESYS library repo for the job manager (cannot recall what its name is), maybe it can help you out.