Listening to Multicast.

Eric Newhuis <>
Mon Apr 26 21:57:58 CEST 2004


No.  He's looking for information on how to do a recvfrom on an IP 
multicast channel, which is essentially a UDP datagram after joining 
the multicast group.  (IP class D addressing)

 From http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/18925 
...

Berkeley Sockets Multicast APIs The Berkeley Sockets Multicast APIs are 
the same as those described by Steve Deering (as mentioned earlier).  
They complement the existing Berkeley Sockets APIs, which were designed 
to allow creating of network applications using virtually any network 
protocol suite, including TCP/IP, the so-called “Internet address 
family.” All of the Berkeley multicast APIs use the setsockopt() 
“socket option” function to initiate their actions  (and for some 
options, the getsockopt() function is also available to retrieve the 
current setting). IP_ADD_MEMBERSHIP to join a multicast group on a 
specific interface IP_DROP_MEMBERSHIP to leave a multicast group (no 
protocol action initiated with IGMP v1, but there is with IGMP v2) 
IP_MULTICAST_IF to set or get default interface for use with multicast 
sends IP_MULTICAST_LOOP to disable loopback of outgoing multicast 
datagrams IP_MULTICAST_TTL to set the IP time-to-live of outgoing 
multicast datagrams. Table 2: Summary of BSD set/getsockopt() multicast 
commands The setsockopt() IP_ADD_MEMBERSHIP function is the most 
significant of all the APIs, in several respects.  It is required to 
receive any datagrams destined for the specified multicast (group) 
address.  Unlike other socket options, it actually initiates some 
network activity; it causes the underlying IP protocol stack to issue 
an IGMP (Internet Group Message Protocol) host membership report to 
notify the local router(s) of the group membership, as prescribed by 
RFC 1112. For an example of how to use these de facto standard 
multicast APIs, see the “Code Samples” section of this white paper.


On Apr 26, 2004, at 2:36 PM, Francesco Cesarini wrote:

> Hi Jeff,
>
> I assume you are looking for process groups. Take a look at 
> http://www.erlang.org/doc/r9c/lib/stdlib-1.12/doc/html/pg.html
>
> Rgds,
> Francesco
> --
> http://www.erlang-consulting.com
>
> Jeffrey M. Einhorn wrote:
>
>> Is there an erlang library that allows you to join a multicast group 
>> and
>> listen to multicast traffic?
>> 	thanks for your time,
>> 		-jeff
>>
>>
>>
>>
>




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