Send echo request to update latency statistics every 5 seconds

Source/dvlnet/base.cpp

@@ -226,6 +226,12 @@ tl::expected<void, PacketError> base::RecvLocal(packet &pkt)
 
 bool base::SNetReceiveMessage(uint8_t *sender, void **data, size_t *size)
 {
+	uint32_t now = SDL_GetTicks();
+	if (now == 0) now++;
+	if (lastEchoTime == 0 || now - lastEchoTime > 5000) {
+		for (plr_t i = 0; i < Players.size(); i++)
+			SendEchoRequest(i);
+	}
 	poll();
 	if (message_queue.empty())
 		return false;

Source/dvlnet/base.h

@@ -90,6 +90,7 @@ protected:
 private:
 	std::array<PlayerState, MAX_PLRS> playerStateTable_;
 	bool awaitingSequenceNumber_ = true;
+	uint32_t lastEchoTime = 0;
 
 	plr_t GetOwner();
 	bool AllTurnsArrived();