Port forwarding allows external computers to connect with computers within a local area network.
Why Forward Your Ports?
Port forwarding can be very useful if you want to connect to your computer from a remote location. For instance, if you try to SSH into your computer from another using your external IP address, the connection will time out. Why? Because the SSH command is pointing to the router and not a particular computer. The router doesn’t know where to direct the SSH. With port forwarding, you can configure your router to forward any incoming connections to port 22 (the port SSH uses) to a specific computer. These same techniques can be used to host multi-player servers, or even allow you to remotely control computers over the internet with Apple Remote Desktop and SSH.
You do have to keep in mind some of the potential risks with forwarding your ports; your router usually provides some degree of protection from hackers trying to SSH into your computer, and you’re making a door by opening up that port. There’s nothing to stop the hackers from trying to guess or bruteforce your password. If they succeed, they could gain full access to your computer from anywhere. Keep security in mind when forwarding your ports, and as always, remember to create secure passwords.
How do I forward my ports?
The process for port forwarding is different for every router. Thankfully, someone has compiled all of that information (along with screenshots and default router passwords) together into one website.
Portforward.com has router specific guides with screenshots that should help you get started.
They don’t have everything, but their list is pretty extensive.
They also have a list of default router passwords, which will be very useful if you haven’t changed your router password — most people don’t, but you should!
How do I know which ports to forward?
Portforward.com has got that too, including everything from Minecraft Server (port 25565) to Age of Empires III (ports 80 and 2300) and Apple Remote Desktop (ports 3283, 5900, and 5988). Here’s the full list.