simulator: added TCP, general cleanup, lockstep

This adds the option to connect over UDP or TCP for mavlink to the
SITL simulator.

Also, this includes a bunch of general cleanup and refactoring of the
simulator interface code. For instance sending of mavlink messages was
put into separate functions and unneccessary comments were removed.

Also, this now sets the timestamp sent by the SITL simulator in the
HIL_SENSOR message in order to enable lockstep.

src/modules/simulator/simulator.h

@@ -1,7 +1,7 @@
 /****************************************************************************
  *
  *   Copyright (c) 2015 Mark Charlebois. All rights reserved.
- *   Copyright (c) 2018 PX4 Pro Dev Team. All rights reserved.
+ *   Copyright (c) 2018 PX4 Development Team. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -32,9 +32,12 @@
  *
  ****************************************************************************/
 
+
 /**
  * @file simulator.h
- * A device simulator
+ *
+ * This module interfaces via MAVLink to a software in the loop simulator (SITL)
+ * such as jMAVSim or Gazebo.
  */
 
 #pragma once
@@ -65,10 +68,10 @@
 #include <v2.0/mavlink_types.h>
 #include <v2.0/common/mavlink.h>
 #include <lib/ecl/geo/geo.h>
+
 namespace simulator
 {
 
-// FIXME - what is the endianness of these on actual device?
 #pragma pack(push, 1)
 struct RawAccelData {
 	float temperature;
@@ -187,7 +190,8 @@ protected:
 	RType _buf[2];
 };
 
-};
+} // namespace simulator
+
 
 class Simulator : public ModuleParams
 {
@@ -381,10 +385,17 @@ private:
 
 	)
 
+	enum class InternetProtocol {
+		TCP,
+		UDP
+	};
+
 	void poll_topics();
 	void handle_message(mavlink_message_t *msg, bool publish);
 	void send_controls();
-	void pollForMAVLinkMessages(bool publish, int udp_port);
+	void send_heartbeat();
+	void request_hil_state_quaternion();
+	void pollForMAVLinkMessages(bool publish, InternetProtocol ip, int port);
 
 	void pack_actuator_message(mavlink_hil_actuator_controls_t &actuator_msg, unsigned index);
 	void send_mavlink_message(const mavlink_message_t &aMsg);