[c-nsp] Multicast Issue

[John Neiberger]

>>> Antonio Querubin <tony at lava.net> 4/27/06 3:12:57 PM >>>
>On Thu, 27 Apr 2006, John Neiberger wrote:
>
>> The client begins talking to the server via TCP, so it already
>> obviously knows the server's IP address. After it's been talking to
the
>> server for a few seconds (a couple hundred packets) the client sends
a
>> single multicast packet to 224.0.1.55. This is some sort of server
>> location mechanism. But it shouldn't be necessary because the
client
>> obviously already knows the IP address of the server. To make this
even
>> more colossally dumb, the IP address of the server is IN THE DATA
>> PORTION OF THE MULTICAST PACKET! If the client does not receive a
>> unicast response to this multicast packet, the client can't connect,
at
>> least from the user's perspective. Really bad design because that
means
>> that the server doesn't use IGMP to join the group, which means it
has
>> to be on the same LAN as all of the clients. I'm just trying to find
a
>> way to make it work for now until we can talk to the developers of
the
>> application.
>
>Seems that the root of the problem is that the server isn't joining
the 
>group so the fix should be applied there.  Couldn't you just write a
small 
>routine that runs concurrently on the server and joins the group?  And

>then let the router handle multicast normally.

That would be the best way to handle this but I'm not a programmer. I
have no idea how to write a Windows 2003 application that does this.
Perhaps there is an open source IGMP "client" out there somewhere. All
we really need it to do is join the group and make sure it stays
joined.

John
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