how to open a port on a Cisco 1800 series router

I need to open port 5000 on a cisco 1800 series router and i am looking for the commands that will do this. I am trying to go through the manual for this but can not seem to find the right section for what i am looking for

what are the proper commands to open this or any other port on a Cisco

any input on this process is greatly appreciated

Thank you