NAT Tunnel v0.01

If you have access to a server with public IP and unfiltered ports you can run NAT Tunnel (NT) server on the server, and NT client on your box behind NAT. the server requires 2 open ports: one for communication with the NT client (--admin), the other for regular clients to connect to (--public: this is the port you want your users to use).

The NT client opens a connection to the server's admin ip/port. As soon as the server receives a new connection, it signals the NT client, which then creates a new tunnel connection to the server, which is then connected to the desired service on the NT client's side (--local)

The connection between NT Client and NT Server on the admin interface is protected by a shared secret against unauthorized use. An adversary who can intercept packets could crack the secret if it's of insufficient complexity. At least 10 random characters and numbers are recommended.

Example: You have a HTTP server listening on your local machine on port 80. You want to make it available on your cloud server/VPS/etc's public IP on port 7000. We use port 8000 on the cloud server for the control channel.

Server:

natsrv.py --mode server --secret s3cretP4ss --public 0.0.0.0:7000 --admin 0.0.0.0:8000

Client:

natsrv.py --mode client --secret s3cretP4ss --local localhost:80 --admin example.com:8000