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/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,