Find out what port is pointing to a cert

I have tried to ask this in “PC Troubleshooting” with not help, but I didn’t give enough information, so here it goes. What I mean by find out what port is pointing to a certain program, is that like if you have a web server running on port 80, or a trojen on port 2358. You can find out that your port 80 or port 2358 is open and waiting for a connection w/ commands, but you dont know what program the commands goto. That is the reason for my question. If anyone has anymore trouble with my question please email me and I will give you EVEN more detail.