I find it useful to easily open a port, to test access controls. Configuring a webserver or iptables to redirect to a known running port is cumbersome. The following has proved useful many times.
$ echo "open port" |nc -l 8080
Verification can be done with telnet or netcat.
$ telnet example.com 8080
Trying example.com...
Connected to example.com.
Escape character is '^]'.
open port
Connection closed by foreign host.
$ nc example.com 8080
open port