Sidedoor maintains an SSH connection or tunnel with a shell script daemon.

The primary use case is maintaining a remote port forward to the local SSH server (or another port). Thus, the local device can be accessed without using incoming connections that may be blocked by a NAT or firewall or otherwise impractical with mobile devices.

SSH clients can connect to the device via the reverse SSH proxy that sidedoor tunnels to. This proxy server can be untrusted and run by a third party or cloud service.

sidedoor enables SSH keepalives and retries SSH with exponential backoff. In order to reconnect as soon as possible, it resets the backoff when a network interface is brought up (or changed).

Refer to the sidedoor man page to configure and set SSH keys.