Caveats:
* requiretty must be disabled in the sudoers config
* asking for a password doesn't work yet, so any sudoers users must
be configured with NOPASSWD
* if not starting the daemon as root, the user running the daemon
must have sudoers entries to allow them to run the command as the
target sudo_user
Still needs:
* chunked file transfer/receive
* should probably move all send/recv operations to separate
functions to reduce code duplication
* initial connection setup over ssh? or do we handle that in runner?
