[erlang-questions] Struggling with multicast udp send

Jarrod Roberson <>
Sat Dec 5 07:11:26 CET 2009

On Mon, Nov 16, 2009 at 2:21 AM, Rapsey <> wrote:
> The code I pasted was for sending. I use it to transmit an IPTV multicast
> video stream. Why is source port important? If you wish to also receive on
> that port, you could always have a different regular udp socket used just
> for listening.
> Sergej

Source port is important because of the way the spec is written.

" If the source UDP port in a received Multicast DNS Query is not port
   5353, this indicates that the client originating the query is a
   simple client that does not fully implement all of Multicast DNS.
   In this case, the Multicast DNS Responder MUST send a UDP response
   directly back to the client, via unicast, to the query packet's
   source IP address and port. This unicast response MUST be a
   conventional unicast response as would be generated by a conventional
   unicast DNS server; for example, it MUST repeat the query ID and the
   question given in the query packet.

any other source port than 5353 implies my client is not a compliant client.
So I have to be able to send on source port 5353. I have tried
multiple sockets, same socket,
nothing lets me send on 5353. I have Java, Python, C, C++ that all
work on OSX, Windows, Linux and Solaris that
let me do this without any problems.

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