Use alternate dns name if name resolution fails for internet server (6dns.org seems to be unreliable, but is still the only one to provide both ipv4 and ipv6 name resolution for free).

src/net/clientcontext.h

@@ -47,6 +47,10 @@ public:
 	{return m_serverAddr;}
 	void SetServerAddr(const std::string &serverAddr)
 	{m_serverAddr = serverAddr;}
+	const std::string &GetAlternateServerAddr() const
+	{return m_alternateServerAddr;}
+	void SetAlternateServerAddr(const std::string &serverAddr)
+	{m_alternateServerAddr = serverAddr;}
 	unsigned GetServerPort() const
 	{return m_serverPort;}
 	void SetServerPort(unsigned serverPort)
@@ -79,6 +83,7 @@ private:
 	int					m_protocol;
 	int					m_addrFamily;
 	std::string			m_serverAddr;
+	std::string			m_alternateServerAddr;
 	unsigned			m_serverPort;
 	std::string			m_password;
 	sockaddr_storage	m_clientSockaddr;

src/net/clientthread.h

@@ -48,6 +48,7 @@ public:
 	// (i.e. after starting the thread).
 	void Init(
 		const std::string &serverAddress,
+		const std::string &alternateServerAddress,
 		unsigned serverPort,
 		bool ipv6,
 		bool sctp,

src/net/common/clientthread.cpp

@@ -70,7 +70,8 @@ ClientThread::~ClientThread()
 
 void
 ClientThread::Init(
-	const string &serverAddress, unsigned serverPort, bool ipv6, bool sctp,
+	const string &serverAddress, const string &alternateServerAddress,
+	unsigned serverPort, bool ipv6, bool sctp,
 	const string &pwd, const string &playerName, const string &avatarFile)
 {
 	if (IsRunning())
@@ -84,6 +85,7 @@ ClientThread::Init(
 	context.SetProtocol(sctp ? SOCKET_IPPROTO_SCTP : 0);
 	context.SetAddrFamily(ipv6 ? AF_INET6 : AF_INET);
 	context.SetServerAddr(serverAddress);
+	context.SetAlternateServerAddr(alternateServerAddress);
 	context.SetServerPort(serverPort);
 	context.SetPassword(pwd);
 	context.SetPlayerName(playerName);

src/net/common/resolverthread.cpp

@@ -45,6 +45,7 @@ ResolverThread::Init(const ClientContext &context)
 
 	GetContext().SetAddrFamily(context.GetAddrFamily());
 	GetContext().SetServerAddr(context.GetServerAddr());
+	GetContext().SetAlternateServerAddr(context.GetAlternateServerAddr());
 	GetContext().SetServerPort(context.GetServerPort());
 }
 
@@ -78,6 +79,19 @@ ResolverThread::Main()
 		context.GetProtocol(),
 		(struct sockaddr *)context.GetClientSockaddr(),
 		context.GetClientSockaddrSize());
+
+	if (!m_retVal && !context.GetAlternateServerAddr().empty())
+	{
+		// Try alternate name.
+		m_retVal = socket_resolve(
+			context.GetAlternateServerAddr().c_str(),
+			tmpStr.str().c_str(),
+			context.GetAddrFamily(),
+			SOCK_STREAM,
+			context.GetProtocol(),
+			(struct sockaddr *)context.GetClientSockaddr(),
+			context.GetClientSockaddrSize());
+	}
 }
 
 const ClientContext &

src/session.cpp

@@ -162,8 +162,13 @@ void Session::startInternetClient()
 	}
 
 	myNetClient = new ClientThread(*myGui, *myAvatarManager);
+	string internetServerAddr(myConfig->readConfigString("InternetServerAddress"));
+	string alternateServerAddr;
+	if (internetServerAddr == "pokerth.6dns.org")
+		alternateServerAddr = "pokerth.dyndns.org";
 	myNetClient->Init(
-		myConfig->readConfigString("InternetServerAddress"),
+		internetServerAddr,
+		alternateServerAddr,
 		myConfig->readConfigInt("InternetServerPort"),
 		myConfig->readConfigInt("InternetServerUseIpv6") == 1,
 		myConfig->readConfigInt("InternetServerUseSctp") == 1,
@@ -185,6 +190,7 @@ void Session::startNetworkClient(const string &serverAddress, unsigned serverPor
 	myNetClient = new ClientThread(*myGui, *myAvatarManager);
 	myNetClient->Init(
 		serverAddress,
+		"",
 		serverPort,
 		ipv6,
 		sctp,
@@ -209,6 +215,7 @@ void Session::startNetworkClientForLocalServer(const GameData &gameData)
 	const char *loopbackAddr = useIpv6 ? "::1" : "127.0.0.1";
 	myNetClient->Init(
 		loopbackAddr,
+		"",
 		myConfig->readConfigInt("ServerPort"),
 		useIpv6,
 		myConfig->readConfigInt("ServerUseSctp") == 1,