public String getId() {
            return id;
        }
Returns an arbitrary, opaque, unique ID for this connection. If
defined, this ID may be used via the "join" (primaryConnection)
property of another connection to join (share) this connection while
it is in progress.

@return
   An arbitrary, opaque, unique ID for this connection.
extensions/guacamole-auth-json/src/main/java/org/apache/guacamole/auth/json/user/UserData.java