Reverse port forwarding can be referred to as reverse tunnel. Reverse tunnel is a very useful way to access some application on the computer that behind a restricted or tight Firewall/Gateway/Router. For security concern, a lots of administrators will configure Firewall/Gateway/Router to refuse the connection from outside. So you just can not directly access those computers without reverse tunnel technology. Normally, reverse tunnel include two components. One you can call client component and the other is server component. You should deploy the client component on the side of the computer that behind Firewall/Gateway/Rourter and the server component on the side of your computer. The client and server component will automatically create a session connection to control reverse tunnel. The server component will listen on a port that you can connect. So when you access the port of server component. The server component will control the client component to create a reverse tunnel connection to the server component. The Firewall/Gateway/Router will not restrict this. Then client component can receive data from server component and port forwarding to the application on the computer that behind Firewall/Gateway/Router. This is the basic idea of reverse tunnel that can let you access some application that you can not directly access.