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Non-blocking UDP listener issue

2017-01-12
2019-07-19
  • RichardVerzijl - 2017-01-12

    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

     
  • RichardVerzijl - 2017-01-13

    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

     
  • aliazzz

    aliazzz - 2019-07-19

    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.

     

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