public default String getProtocol() {
        return null;
    }
Returns the name of the protocol to be used. If the protocol is not
known or the implementation refuses to reveal the underlying protocol,
null is returned.

<p>Implementations <strong>should</strong> aim to expose the name of the
underlying protocol, such that protocol-specific responses like the
"required" and "argv" instructions can be handled correctly by code
consuming the GuacamoleSocket.

@return
    The name of the protocol to be used, or null if this information is
    not available.
guacamole-common/src/main/java/org/apache/guacamole/net/GuacamoleSocket.java