How to specify a network interface when making net requests from Node.js? - node.js

Question

In either http.request or net.connect, is there an option that I can specify a network interface to initiate a connection?
EDIT: AFAIK in OS level I can specify address level, or load balancing into routing tables. But the way of interface choosing in my software is more than that, I wanna know if I can do that in codes.

Answer 1

Node has this built in:
http://nodejs.org/api/net.html#net_net_connect_options_connectionlistener
http://nodejs.org/api/http.html#http_http_request_options_callback
See localAddress, just set that to the IP of the interface you'd like to use.

Answer 2

EDIT: As mak pointed out, it is indeed possible to specify a network interface from a user process. I stand corrected. However, I haven't yet found a module that allows it with node.
By default, the network interface is determined by the OS routing table.
You can list this table with netstat -r on Unix systems (OSX included). Just open a terminal and type the command. You will get a listing like:
laurent ~ $ netstat -r
Routing tables
Internet:
Destination Gateway Flags Refs Use Netif Expire
default 192.168.1.1 UGSc 153 0 en0
127 localhost UCS 0 0 lo0
localhost localhost UH 2 42 lo0
...
The Netif field gives you the network interface used for the route. You can also get the interface used to reach a hostname with route:
laurent ~ $ route get google.fr
route to: par03s02-in-f23.1e100.net
destination: default
mask: default
gateway: 192.168.1.1
interface: en0
flags: <UP,GATEWAY,DONE,STATIC,PRCLONING>
recvpipe sendpipe ssthresh rtt,msec rttvar hopcount mtu expire
0 0 0 0 0 0 1500 0
This is more a serverfault thing, but you can change routes with the route command. For example, this will route traffic to X.Y.Z.[0-254] to X.Y.Z.254 on eth0:
route add -net X.Y.Z.0/24 gw X.Y.Z.254 dev eth0
If you want routes to persist a reboot, you can add them to /etc/network/interfaces. If you want to load balance between several different routes, you should also check MPLS.

Answer 3

You can use node cURL wrapper
curl = require('node-curl')
curl('www.google.com', { INTERFACE: 'eth1', RAW: 1 }, function(err) {
console.info(this);
});