python: urllib2 using different network interface

Question

I have the following code:

f = urllib2.urlopen(url)
data = f.read()
f.close()

It's running on a machine with two network interfaces. I'd like to specify which interface I want the code to use. Specifically, I want it to use the one other than the one it is using by default... but I can figure out which is which if I can just pick the interface.

What's the easiest/best/most pythonic way to do this?

Hebraist

I assume you can't change the system route values to force connection to your remote server use the other interface ? – Debera

@CédricJulien: That would work (if I could make all connections to a particular web-site go through the other interface), though I'm also interested to know how to do it in-code if possible. – Hebraist

Answer 1

Not yet a complete solution, but if you were using only simple socket objects, you could do what you need this way :

import socket
s = socket.socket()
s.bind(("127.0.0.1", 0))    # replace "127.0.0.1" by the local IP of the interface to use
s.connect(("remote_server.com", 80))

Thus, you will force the system to bind the socket to the wanted network interface.

Boatsman

If you're using linux, this recipe will be useful to map from interface name to IP address. – Thespian

Answer 2

If you use Twisted's twisted.web.client.Agent, then you can achieve this via:

from twisted.internet import reactor
from twisted.web.client import Agent

agent = Agent(reactor, bindAddress=("10.0.0.1", 0))

And then using agent in the usual way.

Handwork