new socket issue

Mark Geib mark.geib.44@REDACTED
Thu Feb 4 23:04:34 CET 2021

In order to join a source-specific multicast group I am trying the new socket module. I am able to join the multicast and start receiving datagrams by spawning the function below. The gen_udp module does not support joining a source-specific multicast currently.

active_socket(Socket, Parent, Timeout) ->
  case socket:recvfrom(Socket, 0, [], Timeout) of
    {ok, {#{port := Port, addr := Addr}, Data}} ->
      Parent ! {udp, Addr, Port, Data},
      active_socket(Socket, Parent, Timeout);

    {error, Reason} ->
      Parent ! {error, socket, Reason},
      active_socket(Socket, Parent, Timeout)


The multicast is a 45Mb RTP MPEG-TS stream. I am able to receive and verify the RTP sequence number successfully. However, about every Timeout period, in the function above, there are a number of datagrams dropped, that is, the RTP sequence number has a gap of about 200. This continues to happen as long as the process runs. Between the drops everything looks fine.

As you can see, my approach is to simply have a recvfrom pending at all times so when a datagram arrives the recvfrom returns, I forward the datagram and call recvfrom again. The Timeout is simply to avoid recvfrom returning with no data.


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 528 bytes
Desc: Message signed with OpenPGP
URL: <>

More information about the erlang-questions mailing list