The host behind the NAT that runs `rathole` in the client mode. It has some services that need to be forwarded.
### Visitor
Who visists a *service*, via the *server*
### Control Channel
A control channel is a TCP connection between the *server* and the *client* that only carries `rathole` control commands for one *service*.
### Data Channel
A data channel is a TCP connection between the *server* and the *client* that only carries the encapsulated data that needs forwarding for one *service*.
## The Process
*TODO: Add more details about the protocol*
When `rathole` starts in the client mode, it creates connections to `server.common.bind_addr` for each service. These connection acts as control channels.
When a control channel starts, the server challenge the client by a nonce, the client is required to authenticate as the service it wants to represent. Then the forwarding of that service is set up.
When the server accepts a connection on a service's `bind_port`, it sends a control command to the client via the corresponding control channel. Then the client connects to the server to create a data channel. In this way, a forwarding is set up. The server also creates a few data channels in advance to improve the latency.
