Re: UDP and OT
Re: UDP and OT
- Subject: Re: UDP and OT
- From: <email@hidden>
- Date: Fri, 13 Dec 2002 13:58:36 +0000
- Organization: Coderus Ltd
>
In this case I would just set the IP_TTL to 1.
>
Agreed.
>
>
Well, if you're feeling adventurous, you could incorporate the Darwin
>
Rendezvous code into your application. The Rendezvous code is split
>
into a common core (which is in portable C) and a platform layer.
>
Writing a platform layer isn't too difficult, and we actually include
>
a Mac OS 9 platform layer as part of the source distribution.
>
Hmmm interesting, its an option, although does it support pre 10.2 system
I guess so.
>
I don't understand what you're saying here. My suggestion was to use
>
IP multicast instead of using IP broadcast. The advantage of using
>
multicast is that, when you send a packet, only machines that are
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subscribed to that particular multicast address will receive it. The
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rest of them will filter it out in hardware. OTOH, if you broadcast,
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every machine receives the broadcast and, if you're software isn't
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running, throw the packet away in softwar.
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Sounds like a good idea for hardware filtering on non subscribed machines.
From what I have been reading on multicast in setting up the
struct TIPAddMulticast {
InetHost multicastGroupAddress;
InetHost interfaceAddress;
};
interfaceAddress is obviously the IP address of the hardware.
MulticastGroupAddress isn't very clear as what you should use here, as I
found some text which says :-
<snip>
Multicast address are like IP addresses used for single hosts, and is
written in the same way: A.B.C.D. Multicast addresses will never clash with
host addresses because a portion of the IP address space is specifically
reserved for multicast. This reserved range consists of addresses from
224.0.0.0 to 239.255.255.255. However, the multicast addresses from
224.0.0.0 to 224.0.0.255 are reserved for multicast routing information;
Application programs should use multicast addresses outside this range.
</snip>
So following that any address with that range e.g. 225.0.0.37 (And this will
never clash with a host IP address is this actually true and enforced ???)
So if that9s correct, the example I found said that if you are sending this
broadcast you send it to the above address (Multicast address), and you
don't need to join the multicast group unless you want to receive this
multicast.
As I understand that you can send to a multicast group, if you are not a
member of the group which is fine, (hopefully not a host address)
(Here the link I found with text and unix sample)
http://ganges.cs.tcd.ie/undergrad/4ba2/multicast/antony/index.html
Codewise, its just looks to me that you send to a multicast address, and to
receive just by joining the multicast group, does this sound right ???.
Thanks
Mark.
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