diff --git a/Core/GameEngine/Source/GameNetwork/GameSpy/MainMenuUtils.cpp b/Core/GameEngine/Source/GameNetwork/GameSpy/MainMenuUtils.cpp
index f35a947ae0e..922e7ed3f5b 100644
--- a/Core/GameEngine/Source/GameNetwork/GameSpy/MainMenuUtils.cpp
+++ b/Core/GameEngine/Source/GameNetwork/GameSpy/MainMenuUtils.cpp
@@ -44,6 +44,8 @@
 #include "GameClient/ShellHooks.h"
 
 #include "gamespy/ghttp/ghttp.h"
+// Must follow ghttp.h: gsavailable.h uses gsi_char without including gsplatform.h.
+#include "gamespy/gsavailable.h"
 
 #include "GameNetwork/DownloadManager.h"
 #include "GameNetwork/GameSpy/BuddyThread.h"
@@ -59,6 +61,23 @@
 
 static Bool checkingForPatchBeforeGameSpy = FALSE;
 static Int checksLeftBeforeOnline = 0;
+
+// Every GameSpy SDK entry point fails until this reaches GSIACAvailable.
+static GSIACResult availableCheckResult = GSIACWaiting;
+// Tracked separately from the result so a cancelled check cannot decrement
+// checksLeftBeforeOnline after CancelPatchCheckCallback() has reset it.
+static Bool availableCheckInProgress = FALSE;
+
+static const char *getGameSpyGameName()
+{
+#if RTS_GENERALS
+	return "ccgenerals";
+#elif RTS_ZEROHOUR
+	return "ccgenzh";
+#else
+#error "No GameSpy gamename defined for this build target"
+#endif
+}
 static Int timeThroughOnline = 0; // used to avoid having old callbacks cause problems
 static Bool mustDownloadPatch = FALSE;
 static Bool cantConnectBeforeOnline = FALSE;
@@ -140,6 +159,13 @@ static void noPatchBeforeOnlineCallback()
 	}
 }
 
+// noPatchBeforeOnlineCallback() cannot be reused here: it calls startOnline(), which
+// would fail the same check and reopen this box.
+static void backendUnavailableCallback()
+{
+	HandleCanceledDownload();
+}
+
 ///////////////////////////////////////////////////////////////////////////////////////
 
 static Bool hasWriteAccess()
@@ -216,6 +242,15 @@ static void startOnline()
 
 	TheScriptEngine->signalUIInteract(TheShellHookNames[SHELL_SCRIPT_HOOK_MAIN_MENU_ONLINE_SELECTED]);
 
+	if (availableCheckResult != GSIACAvailable)
+	{
+		// Backend reported the title disabled; the GameSpy threads would all fail to start.
+		MessageBoxOk(TheGameText->fetch("GUI:GSErrorTitle"),
+			TheGameText->fetch("GUI:GSDisconReason4"),
+			backendUnavailableCallback);
+		return;
+	}
+
 	DEBUG_ASSERTCRASH( !TheGameSpyBuddyMessageQueue, ("TheGameSpyBuddyMessageQueue exists!") );
 	DEBUG_ASSERTCRASH( !TheGameSpyPeerMessageQueue, ("TheGameSpyPeerMessageQueue exists!") );
 	DEBUG_ASSERTCRASH( !TheGameSpyInfo, ("TheGameSpyInfo exists!") );
@@ -555,6 +590,11 @@ void CancelPatchCheckCallbackAndReopenDropdown()
 void CancelPatchCheckCallback()
 {
 	s_asyncDNSLookupInProgress = FALSE;
+	if (availableCheckInProgress)
+	{
+		GSICancelAvailableCheck();
+		availableCheckInProgress = FALSE;
+	}
 	HandleCanceledDownload(FALSE); // don't dropdown
 	checkingForPatchBeforeGameSpy = FALSE;
 	checksLeftBeforeOnline = 0;
@@ -730,7 +770,7 @@ DWORD WINAPI asyncGethostbynameThreadFunc( void * szName )
 
 ///////////////////////////////////////////////////////////////////////////////////////
 
-int asyncGethostbyname(char * szName)
+int asyncGethostbyname(const char * szName)
 {
 	static int            stat = 0;
 	static unsigned long  threadid;
@@ -739,7 +779,8 @@ int asyncGethostbyname(char * szName)
 	{
 		/* Kick off gethostname thread */
 		s_asyncDNSThreadDone = FALSE;
-		s_asyncDNSThreadHandle = CreateThread( nullptr, 0, asyncGethostbynameThreadFunc, szName, 0, &threadid );
+		s_asyncDNSThreadHandle = CreateThread( nullptr, 0, asyncGethostbynameThreadFunc,
+			const_cast<char *>(szName), 0, &threadid );
 
 		if( s_asyncDNSThreadHandle == nullptr )
 		{
@@ -773,8 +814,7 @@ void HTTPThinkWrapper()
 {
 	if (s_asyncDNSLookupInProgress)
 	{
-		Char hostname[] = "servserv.generals.ea.com";
-		Int ret = asyncGethostbyname(hostname);
+		Int ret = asyncGethostbyname("servserv.generals.ea.com");
 		switch(ret)
 		{
 		case LOOKUP_FAILED:
@@ -787,6 +827,30 @@ void HTTPThinkWrapper()
 		}
 	}
 
+	// GSIAvailableCheckThink() is what advances the check; it has to be called until it
+	// stops returning GSIACWaiting. Completing counts as one of checksLeftBeforeOnline so
+	// startOnline() waits for it, the same way it waits for the HTTP fetches.
+	if (availableCheckInProgress)
+	{
+		availableCheckResult = GSIAvailableCheckThink();
+		if (availableCheckResult != GSIACWaiting)
+		{
+			availableCheckInProgress = FALSE;
+			--checksLeftBeforeOnline;
+			DEBUG_ASSERTCRASH(checksLeftBeforeOnline>=0, ("Too many callbacks"));
+			if (onlineCancelWindow && checksLeftBeforeOnline == 0)
+			{
+				TheWindowManager->winDestroy(onlineCancelWindow);
+				onlineCancelWindow = nullptr;
+			}
+
+			DEBUG_LOG(("Availability check returned %d", availableCheckResult));
+
+			if (checksLeftBeforeOnline == 0)
+				startOnline();
+		}
+	}
+
 	if (isHttpOk)
 	{
 		try
@@ -829,8 +893,7 @@ void StartPatchCheck()
 		TheGameText->fetch("GUI:CheckingForPatches"), CancelPatchCheckCallbackAndReopenDropdown);
 
 	s_asyncDNSLookupInProgress = TRUE;
-	Char hostname[] = "servserv.generals.ea.com";
-	Int ret = asyncGethostbyname(hostname);
+	Int ret = asyncGethostbyname("servserv.generals.ea.com");
 	switch(ret)
 	{
 	case LOOKUP_FAILED:
@@ -847,7 +910,12 @@ void StartPatchCheck()
 
 static void reallyStartPatchCheck()
 {
-	checksLeftBeforeOnline = 4;
+	checksLeftBeforeOnline = 5;  // the four ghttp calls below, plus the availability check
+
+	GSICancelAvailableCheck();  // going online is retryable; do not leak the old socket
+	availableCheckResult = GSIACWaiting;
+	availableCheckInProgress = TRUE;
+	GSIStartAvailableCheck(getGameSpyGameName());
 
 	std::string gameURL, mapURL;
 	std::string configURL, motdURL;
diff --git a/Core/GameEngine/Source/GameNetwork/GameSpy/Thread/PeerThread.cpp b/Core/GameEngine/Source/GameNetwork/GameSpy/Thread/PeerThread.cpp
index 178a1b1ad3c..def21481106 100644
--- a/Core/GameEngine/Source/GameNetwork/GameSpy/Thread/PeerThread.cpp
+++ b/Core/GameEngine/Source/GameNetwork/GameSpy/Thread/PeerThread.cpp
@@ -1192,6 +1192,18 @@ void PeerThreadClass::Thread_Function()
 
 	peer = peerInitialize( &callbacks );
 	DEBUG_ASSERTCRASH( peer != nullptr, ("null peer!") );
+	if (peer == nullptr)
+	{
+		// The assert above is a no-op in release, where the null goes on to fault in
+		// peerSetRoomWatchKeys(). startThread() reuses this object, so the flags have
+		// to be cleared or they leak into the next attempt.
+		markAsDisconnected();
+		PeerResponse resp;
+		resp.peerResponseType = PeerResponse::PEERRESPONSE_DISCONNECT;
+		resp.discon.reason = DISCONNECT_COULDNOTCONNECT;
+		TheGameSpyPeerMessageQueue->addResponse(resp);
+		return;
+	}
 	m_isConnected = m_isConnecting = false;
 
 	qr2_register_key(EXECRC_KEY, EXECRC_STR);