I have 3 machines:
- Machine A - local network
- Machine B - local network
- Machine C - external network
Local network has a dynamic IP and Dyndns is set up to forward it.
I have ssh on Machine B listening on port 22. Router is set to forward port 22 to Machine B. All works fine:
- Machine A can ssh to Machine B
- Machine C can ssh to Machine B
Next I set up ssh on Machine B listening to port 6234. Router is set to forward 6234 to Machine B.
- Machine A can ssh to Machine B -p 6234
- Machine C gets "Connection timed out"
WhatsMyIp.org port scanner reports port 6234 is open.
Note: the same thing happens using httpd - port 80 works fine, but other ports do not.
So, how can I find out what is blocking the port?