multicast: same port, different IP address?

From: Matt Garman
Date: Wed Apr 08 2009 - 12:43:07 EST


I don't really understand what the concept of a port is in Linux with
regards to multicast.

Basically, I want to use multicast on an internal network with many
nodes. I want to use multicast IP addresses to delineate the message
*type*. E.g., 239.0.0.1 for status monitoring, 239.0.0.2 for control
messages, 239.0.0.3 for heartbeats, 239.0.0.4 for chatting, etc etc.

Since I'm using the address space to delineate messages, can I just
hard-code my port (i.e. make it always the same)?

Put another way: what is the effect of having one host subscribe to
multiple multicast streams, where each stream has the same port, but a
different ip address? Is there a performance impact?

Thanks,
Matt
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