Ruby socket binding on system w/ multiple interfaces - ruby

Question

I have a computer with 2 interfaces, eth0 (192.168.251.10) and eth1 (192.168.251.11), and I'm trying to have two instances of a Ruby application listen on each of them. They should both listen on the same port, just on different interfaces. The interface to be binded to specified via command line args during runtime.
Regardless of the order I start the application, the one listening on eth0 will always succeed, but the one listening on eth1 will always not receive anything. I checked using Wireshark and shows the packets are being received, but is the Ruby application isn't getting anything.
I've tried with a very simple textbook case code, so I'm very puzzled as to why it doesn't work
BasicSocket.do_not_reverse_lookup = true
socket = UDPSocket.new
ip_addr = ARGV[0]
port = 8722
socket.bind(ip_addr, port)
puts "Listener started on #{ip_addr}:#{port}"
while(true)
msg, sender_sockaddr = socket.recvfrom(1024)
end
I'm running Ruby 1.8.7 on Ubuntu 12.04 LTS. Something else I noticed is that if I bring down both the interfaces, and then up again, it will work on the first interface that was brought up, but not the second.
Output from netstat seems correct, showing listening on two different addresses.
Proto Recv-Q Send-Q Local Address Foreign Address State
udp 0 0 0.0.0.0:68 0.0.0.0:*
udp 0 0 192.168.251.10:8722 0.0.0.0:*
udp 0 0 192.168.251.11:8722 0.0.0.0:*
udp 0 0 0.0.0.0:5353 0.0.0.0:*
udp 0 0 0.0.0.0:54506 0.0.0.0:*
udp6 0 0 :::38033 :::*
udp6 0 0 :::5353 :::*

Answer 1

This is not a standard way to setup an app. Hard coding networking assignments is not recommended. You'd be better of using a load balancer and let it handle the interface assignments.