Question

I have a Python script that is running on a Linux server that has a dozen IP addresses associated with it. I implemented a TCPSServer from Python’s socketserver library and had it listen on all network interfaces.

Several devices will be connecting to this server, and we need to be able to somehow capture the ip address of the destination (not the IP address of the client, but the IP address of the server that the client thinks it is connecting to). Right now, I can receive client connections, I can see the client IP, but I cannot figure out a method for obtaining the destination IP.

Does anyone know a method for capturing the destination IP on the socketserver class? It would seem if I can listen to multiple interfaces, there would be a way to tell which interface was hit.

This will be installed on several servers eventually, each with an unknown number of network interfaces. However, we do know that this will only exist on Linux bases systems. So if there was an OS specific way to do this, I would be fine with that as well.

Answer 1

If you have a socket object, you can use socket.getsockname() to obtain the IP address it’s bound to. So something along the lines of:

# IPv4
client = listening_socket.accept()
(ipv4,port) = client.getsockname()

# IPv6
client = listening_socket.accept()
(address, port, flow_info, scope_id) = client.getsockname()

Never tested it on a multihomed server with a socket bound to all interfaces though – might return IPv4 0.0.0.0 or the IPv6 equivalent, for all I know, which wouldn’t be all that useful.