Merge pull request #3981 from IvanSavenko/asio_fix

Simple workaround to fix vcmiserver shutdown procedure

lib/network/NetworkConnection.cpp

@@ -127,6 +127,11 @@ void NetworkConnection::onPacketReceived(const boost::system::error_code & ec, u
 	startReceiving();
 }
 
+void NetworkConnection::setAsyncWritesEnabled(bool on)
+{
+	asyncWritesEnabled = on;
+}
+
 void NetworkConnection::sendPacket(const std::vector<std::byte> & message)
 {
 	std::lock_guard<std::mutex> lock(writeMutex);
@@ -134,14 +139,27 @@ void NetworkConnection::sendPacket(const std::vector<std::byte> & message)
 	uint32_t messageSize = message.size();
 	std::memcpy(headerVector.data(), &messageSize, sizeof(uint32_t));
 
-	bool messageQueueEmpty = dataToSend.empty();
-	dataToSend.push_back(headerVector);
-	if (message.size() > 0)
-		dataToSend.push_back(message);
+	// At the moment, vcmilobby *requires* async writes in order to handle multiple connections with different speeds and at optimal performance
+	// However server (and potentially - client) can not handle this mode and may shutdown either socket or entire asio service too early, before all writes are performed
+	if (asyncWritesEnabled)
+	{
 
-	if (messageQueueEmpty)
-		doSendData();
-	//else - data sending loop is still active and still sending previous messages
+		bool messageQueueEmpty = dataToSend.empty();
+		dataToSend.push_back(headerVector);
+		if (message.size() > 0)
+			dataToSend.push_back(message);
+
+		if (messageQueueEmpty)
+			doSendData();
+		//else - data sending loop is still active and still sending previous messages
+	}
+	else
+	{
+		boost::system::error_code ec;
+		boost::asio::write(*socket, boost::asio::buffer(headerVector), ec );
+		if (message.size() > 0)
+			boost::asio::write(*socket, boost::asio::buffer(message), ec );
+	}
 }
 
 void NetworkConnection::doSendData()

lib/network/NetworkConnection.h

@@ -13,7 +13,7 @@
 
 VCMI_LIB_NAMESPACE_BEGIN
 
-class NetworkConnection : public INetworkConnection, public std::enable_shared_from_this<NetworkConnection>
+class NetworkConnection final : public INetworkConnection, public std::enable_shared_from_this<NetworkConnection>
 {
 	static const int messageHeaderSize = sizeof(uint32_t);
 	static const int messageMaxSize = 64 * 1024 * 1024; // arbitrary size to prevent potential massive allocation if we receive garbage input
@@ -25,6 +25,7 @@ class NetworkConnection : public INetworkConnection, public std::enable_shared_f
 
 	NetworkBuffer readBuffer;
 	INetworkConnectionListener & listener;
+	bool asyncWritesEnabled = false;
 
 	void heartbeat();
 	void onError(const std::string & message);
@@ -42,6 +43,7 @@ public:
 	void start();
 	void close() override;
 	void sendPacket(const std::vector<std::byte> & message) override;
+	void setAsyncWritesEnabled(bool on) override;
 };
 
 VCMI_LIB_NAMESPACE_END

lib/network/NetworkInterface.h

@@ -17,6 +17,7 @@ class DLL_LINKAGE INetworkConnection : boost::noncopyable
 public:
 	virtual ~INetworkConnection() = default;
 	virtual void sendPacket(const std::vector<std::byte> & message) = 0;
+	virtual void setAsyncWritesEnabled(bool on) = 0;
 	virtual void close() = 0;
 };
 

lobby/LobbyServer.cpp

@@ -292,6 +292,7 @@ void LobbyServer::sendChatMessage(const NetworkConnectionPtr & target, const std
 
 void LobbyServer::onNewConnection(const NetworkConnectionPtr & connection)
 {
+	connection->setAsyncWritesEnabled(true);
 	// no-op - waiting for incoming data
 }