Possible to "ping" url:port? (OS X-GeekTool)

To check a specific port, you can use telnet:

telnet 127.0.0.1 8080

(The port follows the IP / hostname with a space, not a colon.)

If you get an immediate error, then the port is not available. If telnet hangs, then you have successfully connected to the port. Ctrl + C to kill telnet, then.

This may or may not help with the port forwarding issue, though. It just gets you to that IP and port.

Theres is hping utility that allows you to ping TCP ports. This is also available via homebrew (brew install hping).

backdrift.org gives a simple instructions on how to use hping for this purpose

$ hping -S -p 80 google.com
HPING google.com (eth0 66.249.92.104): S set, 40 headers + 0 data bytes
len=44 ip=66.249.92.104 ttl=47 id=10442 sport=80 flags=SA seq=0 win=5720 rtt=97.7 ms
len=44 ip=66.249.92.104 ttl=47 id=40838 sport=80 flags=SA seq=1 win=5720 rtt=97.7 ms
len=44 ip=66.249.92.104 ttl=47 id=64607 sport=80 flags=SA seq=2 win=5720 rtt=97.7 ms
len=44 ip=66.249.92.104 ttl=47 id=10443 sport=80 flags=SA seq=3 win=5720 rtt=97.7 ms
^C
--- google.com hping statistic ---
4 packets transmitted, 4 packets received, 0% packet loss
round-trip min/avg/max = 97.7/97.7/97.7 ms