Manually opening TCP ports

[Siraj Shaikh]

Hello

I am just wondering if there is a utility (or any feature in FreeBSD)
that allows me to manually open a TCP port on a machine. I am looking
for a way that could either allow me to open ALL or many TCP ports on
a machine.

Also, is there any way of running a service on more than a single
port, or on all or many ports?

Thanks