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I have a embedded Linux device (in it's own private LAN connected to other sensoric devices) that's connected to the Internet. I can already make a secure, direct TCP connection using a proprietary protocol between my computer and the device. That by itself is already a tunnel and I can, for example, connect to SSH daemon on the device (via the tunnel).

Now I'd like to run another tunnel over that TCP connection that gives me more possibilities. Specifically:

  • has a Linux tunnel endpoint, that gets installed on the device
  • has a userfriendly (read: really easy to use) Windows program acting as the local tunnel entry point and and allows the user to configure the desired tunnel parameters (destination point and IP addresses)
  • allows multiple tunnels over one single TCP connection (important, as establishing that connection is relatively slow)
  • preferably supports FTP connections (which won't work if not specifically supported)
  • does not require any kind of authentification (so ssh-tunnels unfortunately can't be used)

Of course I tried to find such a software by googling around, but could not find anything usable...

Pratically, something like this:

  (USER PC) 

+---------+   +-----------+
|   FTP   |-->|           |
| client  |-->| Windows   |   +----------+
+---------+   |  tunnel   |   | existing |
              | server    |-->| tunnel   | ------------->>  INTERNET 
+---------+   |           |   | server   |
| browser |-->| (wanted)  |   +----------+
+---------+   +-----------+    localhost

     . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

                             +----------+   | Linux     |--> l27.0.0.1:80
                             | existing |   |  tunnel   |
     INTERNET  >>------------| tunnel   |-->| client    |-->
                             | client   |   |           |
                             +----------+   | (wanted)  |--> 

                                                   (EMBEDDED DEVICE)

Does such a tool exist or do I really need to write it on my own?

share|improve this question
A Virtual Private Network (VPN) is commonly used in such situations. – Brian Feb 1 '12 at 15:37
Yeah, but to allow access to other devices in the distant LAN I need to do bridging and AFAIK that involves lots of configuration (note that even if I have full software access (root) to the device at the moment, it is already installed a few hundred km from here). – Udo G Feb 1 '12 at 15:53
Regarding authentication, is it impossible to just bundle the authentication password or private-key? – grawity Feb 1 '12 at 16:08
What do you mean with "bundle"? Anyway, yes, I could create an additional dummy Linux user account and use it's password (but it would be much better if no password or private key would be necessary). – Udo G Feb 1 '12 at 16:23
What leads you to believe that a VPN cannot bridge? It is pretty easy to bridge a connection with OpenVPN – Zoredache Feb 1 '12 at 17:43

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