"Before you can use the following solutions, you must become familiar with the concept of port forwarding. Your computer transfers data through a wide assortment of virtual ports. Each port is numbered and is dedicated to a specific purpose. (email usually funnels through port 25 while web content goes through port 80, for instance) For security reasons, your router's firewall is configured to block incoming traffic on most ports by default. If this were not the case, any person or program (malicious or not) would have access to your computer from the internet.
"To use a remote access solution, you must configure your router to accept incoming connections on the port it uses. Most routers have a web-based interface to make this process easier. Typing http://192.168.1.1 or http://192.168.2.1 (the default gateway address, depending on your brand and model of router) into your web browser will probably allow you to access your router's settings. For specific instructions on how to enable port forwarding, check your router documentation.
"When you set up port forwarding for a specific protocol, you are essentially configuring your router to send all incoming data received on that port to a specific computer on your network. This computer is essentially a gateway (no connection to the Gateway brand name). Once you have access to the gateway system, reaching the rest of the network is trivial."
