How do we open a specific port?

I haven't checked this for syntax. From a terminal window, type man ipfw for the man page,
You want something like:

ipfw add allow tcp from any 8888 to any

In the terminal:

sudo ipfw add allow tcp from x to y

x = starting port
y = ending port

If only opening one port, make both x and y the single port number. Your admin password will be requested, and does not echo on the screen.

To close the port(s) again, replace the word "allow" with the word "deny"

Is there a terminal command to reset all the ports to default? I have been experimenting with ports and would like to reset it back to default so no ports are left open.

Thanks very much, look forward to hearing back from you.

I've been having the same problem trying to figure out how to open up port 24800 so I can use synergy to share my keyboard and mouse. So after much searching I found an app with a somewhat lacking user interface that allows you to open and close ports amongst other things. It's free so I guess I shouldn't complain. It's called Waterroof and is a gui wrapper for terminal methods that have been discussed as solutions on this and other threads.

http://www.hanynet.com/waterroof/index.html

Thanks for your help.