Reverse tunneling in Windows.

Try it out: http://eirikb.github.io/Netro/1.0.1/Netro.exe
Warning: Executable, use at your own risk!
Netro works perfectly with mono for Linux / OSX.

I usually fire up ssh -R when I need some reverse tunneling, on any platform. But sometimes I have to tunnel from Windows to Windows, and this is a bit more difficult, as I usually don't have sshd running on Windows servers.
Netro, a bad play on "Metro" is here to help me and others that must do some quick, dirty and simple tunneling on Windows.

Here is an example: The right side in the following figure is behind a firewall, the left side is publicly accessible.

1. Netro A listens for incoming connections, and listens for reverse tunneling.
2. Netro B connects to A for tunneling.
3. When a client connects to A the data will be transferred through the link between A and B.
4. Connection is made on B to desired host:port.
5. Data can now flow both ways.

Figure:

                    ┊
    u               ┆               O
    │               ┆               │ 
┌───┴───┐           ┆           ┌───┴───┐
│       │           ┆           │       │
│   A   ├───ᑕO──────┆───────────┤   B   │
│       │           ┆           │       │
└───────┘           ┆           └───────┘
                    ┆

Netro.exe 5000 localhost:80
Listen on port 5000, send connections/data to localhost on port 80. No reverse tunneling involved (Proxy).

    ┌─────┐
ᑐ───┤     ├───O
    └─────┘

Netro.exe 5000 5001
Listen on port 5000 for normal connections. Listen on port 5001 for reverse tunneling connection.

       u
       │
    ┌──┴──┐
ᑐ───┤     │
    └─────┘

Netro.exe example.com:5001 localhost:80
Open reverse tunneling cunnection against example.com on port 5001. On reverse connections, open connection against localhost on port 80.

   O
   │
┌──┴──┐
│     ├───O
└─────┘

MIT © Eirik Brandtzæg