Multiple socket.io client connections - force new connection

I want to connect from client side to two different node servers that are actually running on the same local ip address but on different ports. The problem is that the first io.connect() succeeds but the second one fails. I've read that in order to get it working, the second io.connect call should include the force new connection property set to true. I tried it but without much success... Here you are a pretty simplified version of my code:

dataSocket = io.connect('https://' + window.document.location.host);
...
socketOut = io.connect(data.url, {'force new connection': true});

Basically, the first connect opens a socket on https://192.168.1.129 (port 443) and the second one on https://192.168.1.129:3000 and it is this last one which fails. Both servers are running and accepting connections during these calls (obviously). The curious thing is that if I replace the private local address with localhost, it works. I'm definetely missing something...

Any suggestions?