How to open Ports through C#?

I'm kind of a beginner at programming, so I don't know what I'm about to ask is even possible. I want to make a TCP/IP connection to a server over WAN.

Both Client and Server programs were made by me they work just fine in a LAN. I'm now trying over a WAN. I know the server IP Address and the Port he's listening from, but as a client I can't make the connection. I supposed it's because the Port is not actually open/available.

How can I make this to happen in the server side? Is there a way for me to start the server (maybe as administrator) and for it to open the Port by itself? Is this a router or Firewall issue?

If I wasn't clear enough, feel free to ask.

Cheers.

PS: Let me put it this way: If I make the connection in a LAN, it works. I set it to the local IP Address (192.168....) and choose whatever port I want and it works just fine. Once I put my public IP provided my ISP, it doesn't. I set the firewall router to accept everything and put a new rule in windows firewall to open port 100. What changed?

Solution

Please check the following list,

Server Firewall rules to exclude the desired port
Router Firewall to exclude the desired port
Check any installed security software blocking your desired port
Last and crucial! Open router interface and configure your NAT settings so the packets running via the desired port are served to your local server IP
If everyhting is fine and your ISP is not blocking the desired port then you will have no problem.
You can also visit canyouseeme.org in order to check that server listening alright!

Kind Regards,
KB