From: Tanaka Akira <akr@...>
Date: 2009-02-07T23:47:47+09:00
Subject: Re: How do I get the destination IP of a received UDP packet?

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.
-- 
Tanaka Akira