pssl:port[:ip]
    Listen on the given SSL port for a connection. By default, connections are not bound to a particular local IP address, but specifying ip limits connections to those from the given ip. The --private-key, --certificate, and --ca-cert options are mandatory when this form is used.

ptcp:port[:ip]
    Listen on the given TCP port for a connection. By default, connections are not bound to a particular local IP address, but ip may be specified to listen only for connections to the given ip.

punix:file
    Listen on the Unix domain server socket named file for a connection.