simulator: fix TCP on Cygwin-Windows

It turns out that `sendto` does not work for TCP on Cygwin-Windows,
instead we need to use `send`. This required some refactoring since we
need to have the internet protocol and the port stored as a member
variable.

This should fix that lockstep SITL simulation was not working on
Windows.

src/modules/simulator/simulator.h

@@ -212,6 +212,11 @@ public:
 		sample(float a, float b, float c) : x(a), y(b), z(c) {}
 	};
 
+	enum class InternetProtocol {
+		TCP,
+		UDP
+	};
+
 	static int start(int argc, char *argv[]);
 
 	bool getRawAccelReport(uint8_t *buf, int len);
@@ -230,6 +235,9 @@ public:
 
 	bool isInitialized() { return _initialized; }
 
+	void set_ip(InternetProtocol ip);
+	void set_port(unsigned port);
+
 private:
 	Simulator() : ModuleParams(nullptr),
 		_accel(1),
@@ -336,6 +344,9 @@ private:
 
 	int				_param_sub;
 
+	unsigned _port = 14560;
+	InternetProtocol _ip = InternetProtocol::UDP;
+
 	bool _initialized;
 	double _realtime_factor;		///< How fast the simulation runs in comparison to real system time
 	hrt_abstime _last_sim_timestamp;
@@ -385,17 +396,12 @@ private:
 
 	)
 
-	enum class InternetProtocol {
-		TCP,
-		UDP
-	};
-
 	void poll_topics();
 	void handle_message(mavlink_message_t *msg, bool publish);
 	void send_controls();
 	void send_heartbeat();
 	void request_hil_state_quaternion();
-	void pollForMAVLinkMessages(bool publish, InternetProtocol ip, int port);
+	void pollForMAVLinkMessages(bool publish);
 
 	void pack_actuator_message(mavlink_hil_actuator_controls_t &actuator_msg, unsigned index);
 	void send_mavlink_message(const mavlink_message_t &aMsg);