QGC Message id parameter (_message.msgid ) check for arming

Hi all,
I’m trying to make arming control on my external ulog streaming so i looked at qgroundcontrol source code how to did this.
in MavlinkProtocol.cc file i found arming check;

// Check for the vehicle arming going by. This is used to trigger log save.
                if (!_vehicleWasArmed && _message.msgid == MAVLINK_MSG_ID_HEARTBEAT) {
                    mavlink_heartbeat_t state;
                    mavlink_msg_heartbeat_decode(&_message, &state);
                    if (state.base_mode & MAV_MODE_FLAG_DECODE_POSITION_SAFETY) {
                        _vehicleWasArmed = true;

How can i get the message id? I research comman mavlink messages and i didnt find any field name about id.

Thanks for help!