From: Gavin Yap <maclaren_sg@...>
Date: 2009-02-08T02:00:46+09:00
Subject: Re: How do I get the destination IP of a received UDP packet?

Tanaka Akira wrote:
> In article <4ee7ef4b9ffa58f7d0d4c81634802cbf@ruby-forum.com>,
>   Gavin Yap <maclaren_sg@yahoo.com.sg> writes:
> 
>> I need to write a server which is able to identify client by
>> destinations.
>>
>> My machine is listening to "0.0.0.0", any IP addrs configured to it.
>> Take for instance, the machine is configured with "192.168.1.10,
>> 172.16.0.10", also listening to "0.0.0.0", allow listening to Broadcast
>> queries, which is also important to my application
> 
> How about using sockets for each IP address and "0.0.0.0"?
> 
> require 'socket'
> 
> s0 = Socket.new(Socket::AF_INET, Socket::SOCK_DGRAM, 0)
> s0.setsockopt(Socket::SOL_SOCKET, Socket::SO_REUSEADDR, 1)
> s0.bind(Socket.sockaddr_in(9999, "0.0.0.0"))
> 
> s1 = Socket.new(Socket::AF_INET, Socket::SOCK_DGRAM, 0)
> s1.setsockopt(Socket::SOL_SOCKET, Socket::SO_REUSEADDR, 1)
> s1.bind(Socket.sockaddr_in(9999, "192.168.1.10"))
> 
> s2 = Socket.new(Socket::AF_INET, Socket::SOCK_DGRAM, 0)
> s2.setsockopt(Socket::SOL_SOCKET, Socket::SO_REUSEADDR, 1)
> s2.bind(Socket.sockaddr_in(9999, "172.16.0.10"))
> 
> while true
>   rs, = IO.select([s0, s1, s2])
>   rs.each {|s|
>     p [Socket.unpack_sockaddr_in(s.getsockname)[1], s.recv(100)]
>   }
> end
> 
> I'm not certain about the portability of the broadcast
> handling, though.

Hi Tanaka Akira san,

Thanks for the tip.

I guess this is the only way get my destination address.
I wonder if there's a way to recieve the packet, with layer 3(IP header) 
and layer 4(UDP header) info.
I dun mind to write a wrapper to strip off or add, the IP header and UDP 
details.

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