Re: Broadcast TCP/IP message to several clients

From:
Knute Johnson <nospam@rabbitbrush.frazmtn.com>
Newsgroups:
comp.lang.java.programmer
Date:
Wed, 12 Aug 2009 13:50:34 -0700
Message-ID:
<4a832b1a$0$13977$b9f67a60@news.newsdemon.com>
markspace wrote:

Knute Johnson wrote:

markspace wrote:

java.net.MulticastSocket ?


No. I'm 90% sure this is something else, don't use this. This is
for a server sending streaming data to multiple clients, and it
requires special network configuration. Most switches and gateways
don't even support it. Regular ol' broadcast is what you want, not
multicast.


Reading the OP's original post, I think he wants to send a signal to
all of his clients to get them to start sending in data. Seems like
the perfect use of multicast to me.


Excpet that, as I mentioned, almost nothing supports multicast, so the
packets will never reach their destination.

Multicasting is kind of an orphan in the TCP/IP spec. It was intended
to solve a problem no one really had, or wanted to solve. As far as I
know, it'll be like pulling teeth to get any network administrators to
configure their networks to support this, if it's even possible at all.
 And if you have to go through an ISP or 3rd party network, forget it.

I could be all wrong, but I'd check with whoever is in charge of the
routers and gateways you'll have to go through before I wrote any lines
of code at all.


I agree if he has to cross any router boundaries he will have problems.
  Inside a local network shouldn't be a problem.

UDP datagrams however can go anywhere. He could just send all of his
clients plain datagrams, a little more coding but not that tough.

--

Knute Johnson
email s/nospam/knute2009/

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