I'm using netcat as a backend to shovel data back and forth for a program I'm making. I tested my program on the local network, and once it worked I thought it would be a matter of simply forwarding a port from my router to have my program work over the internet. Alas! This seems not to be the case.
If I start netcat listening on port 6666 with:
nc -vv -l -p 6666,
then go to 127.0.0.1:6666 in a browser, as expected I see a HTTP GET request come through netcat (and my browser sits waiting in vain). If I go to my.external.ip.address:6666, however, nothing comes through at all and the browser displays 'could not connect to my.external.ip.address:6666'.
I know that the port is correctly forwarded, as www.canyouseeme.org says port 6666 is open (and when netcat is not listening, that its closed).
If I run netcat with -g my.adslmodem's.local.address to set the gateway address, I get the same behavior. Am I using this command line option correctly? Any insight as to what I'm doing wrong?
Best Answer
So, if you scan your system from a system outside your network while netcat is listening to 6666, the outside system sees it's got something running. But when you try from inside your network to connect to your external IP address to route it back in, it's giving an error and netcat shows nothing connecting? I'd almost suspect you're having a routing issue trying to go from your local machine to the router and back in, perhaps a NAT issue with your hardware. What device are you using? You might want to check to see if this is the case by trying to connect to that port (or have a friend try it) from outside your network and see if the result is the same.