diff --git a/src/common/engine/i_net.cpp b/src/common/engine/i_net.cpp
index 33b4c12671..27dbfe0a71 100644
--- a/src/common/engine/i_net.cpp
+++ b/src/common/engine/i_net.cpp
@@ -132,7 +132,8 @@ enum
 	PRE_CONACK,				// Sent from host to guest to acknowledge PRE_CONNECT receipt
 	PRE_ALLFULL,			// Sent from host to an unwanted guest
 	PRE_ALLHEREACK,			// Sent from guest to host to acknowledge PRE_ALLHEREACK receipt
-	PRE_GO					// Sent from host to guest to continue game startup
+	PRE_GO,					// Sent from host to guest to continue game startup
+	PRE_IN_PROGRESS,		// Sent from host to guest if the game has already started
 };
 
 // Set PreGamePacket.fake to this so that the game rejects any pregame packets
@@ -269,6 +270,8 @@ void PacketSend (void)
 	//			I_Error ("SendPacket error: %s",strerror(errno));
 }
 
+void PreSend(const void* buffer, int bufferlen, const sockaddr_in* to);
+void SendConAck(int num_connected, int num_needed);
 
 //
 // PacketGet
@@ -303,7 +306,7 @@ void PacketGet (void)
 					GetPlayerName(node).GetChars());
 			}
 
-			doomcom.data[0] = 0x80;	// NCMD_EXIT
+			doomcom.data[0] = NCMD_EXIT;
 			c = 1;
 		}
 		else if (err != WSAEWOULDBLOCK)
@@ -342,9 +345,13 @@ void PacketGet (void)
 	else if (c > 0)
 	{	//The packet is not from any in-game node, so we might as well discard it.
 		// Don't show the message for disconnect notifications.
-		if (c != 2 || TransmitBuffer[0] != PRE_FAKE || TransmitBuffer[1] != PRE_DISCONNECT)
+		if (TransmitBuffer[0] != NCMD_EXIT)
 		{
-			DPrintf(DMSG_WARNING, "Dropped packet: Unknown host (%s:%d)\n", inet_ntoa(fromaddress.sin_addr), fromaddress.sin_port);
+			if (TransmitBuffer[0] != PRE_FAKE)
+				DPrintf(DMSG_WARNING, "Dropped packet: Unknown host (%s:%d)\n", inet_ntoa(fromaddress.sin_addr), fromaddress.sin_port);
+			// If it's someone waiting in the lobby, let them know the game already started
+			uint8_t msg[] = { PRE_FAKE, PRE_IN_PROGRESS };
+			PreSend(msg, 2, &fromaddress);
 		}
 		doomcom.remotenode = -1;
 		return;
@@ -369,7 +376,22 @@ sockaddr_in *PreGet (void *buffer, int bufferlen, bool noabort)
 		int err = WSAGetLastError();
 		if (err == WSAEWOULDBLOCK || (noabort && err == WSAECONNRESET))
 			return NULL;	// no packet
-		I_Error ("PreGet: %s", neterror ());
+
+		if (doomcom.consoleplayer == 0)
+		{
+			int node = FindNode(&fromaddress);
+			I_NetMessage("Got unexpected disconnect.");
+			doomcom.numnodes--;
+			for (; node < doomcom.numnodes; ++node)
+				sendaddress[node] = sendaddress[node + 1];
+
+			// Let remaining guests know that somebody left.
+			SendConAck(doomcom.numnodes, doomcom.numplayers);
+		}
+		else
+		{
+			I_NetError("The host disbanded the game unexpectedly");
+		}
 	}
 	return &fromaddress;
 }
@@ -708,7 +730,7 @@ bool HostGame (int i)
 
 	doomcom.numnodes = 1;
 
-	I_NetInit ("Waiting for players", numplayers);
+	I_NetInit ("Hosting game", numplayers);
 
 	// Wait for numplayers-1 different connections
 	if (!I_NetLoop (Host_CheckForConnects, (void *)(intptr_t)numplayers))
@@ -783,13 +805,15 @@ bool Guest_ContactHost (void *userdata)
 			}
 			else if (packet.Message == PRE_DISCONNECT)
 			{
-				doomcom.numnodes = 0;
-				I_FatalError ("The host cancelled the game.");
+				I_NetError("The host cancelled the game.");
 			}
 			else if (packet.Message == PRE_ALLFULL)
 			{
-				doomcom.numnodes = 0;
-				I_FatalError ("The game is full.");
+				I_NetError("The game is full.");
+			}
+			else if (packet.Message == PRE_IN_PROGRESS)
+			{
+				I_NetError("The game was already started.");
 			}
 		}
 	}
@@ -850,7 +874,7 @@ bool Guest_WaitForOthers (void *userdata)
 			return true;
 
 		case PRE_DISCONNECT:
-			I_FatalError ("The host cancelled the game.");
+			I_NetError("The host cancelled the game.");
 			break;
 		}
 	}
@@ -875,6 +899,7 @@ bool JoinGame (int i)
 	BuildAddress (&sendaddress[1], Args->GetArg(i+1));
 	sendplayer[1] = 0;
 	doomcom.numnodes = 2;
+	doomcom.consoleplayer = -1;
 
 
 	// Let host know we are here
@@ -1046,6 +1071,13 @@ void I_NetMessage(const char* text, ...)
 #endif
 }
 
+void I_NetError(const char* error)
+{
+	doomcom.numnodes = 0;
+	StartWindow->NetClose();
+	I_FatalError(error);
+}
+
 // todo: later these must be dispatched by the main menu, not the start screen.
 void I_NetProgress(int val)
 {
diff --git a/src/common/engine/i_net.h b/src/common/engine/i_net.h
index c52072c863..15720374d0 100644
--- a/src/common/engine/i_net.h
+++ b/src/common/engine/i_net.h
@@ -7,6 +7,7 @@
 int I_InitNetwork (void);
 void I_NetCmd (void);
 void I_NetMessage(const char*, ...);
+void I_NetError(const char* error);
 void I_NetProgress(int val);
 void I_NetInit(const char* msg, int num);
 bool I_NetLoop(bool (*timer_callback)(void*), void* userdata);
diff --git a/src/common/engine/st_start.h b/src/common/engine/st_start.h
index a8b78aaa83..b09991d04f 100644
--- a/src/common/engine/st_start.h
+++ b/src/common/engine/st_start.h
@@ -55,6 +55,7 @@ public:
 	virtual void NetInit(const char *message, int num_players) {}
 	virtual void NetProgress(int count) {}
 	virtual void NetDone() {}
+	virtual void NetClose() {}
 	virtual bool NetLoop(bool (*timer_callback)(void *), void *userdata) { return false; }
 	virtual void AppendStatusLine(const char* status) {}
 	virtual void LoadingStatus(const char* message, int colors) {}
@@ -74,6 +75,7 @@ public:
 	void NetProgress(int count);
 	void NetMessage(const char* format, ...);	// cover for printf
 	void NetDone();
+	void NetClose();
 	bool NetLoop(bool (*timer_callback)(void*), void* userdata);
 protected:
 	int NetMaxPos, NetCurPos;
diff --git a/src/common/platform/win32/i_mainwindow.cpp b/src/common/platform/win32/i_mainwindow.cpp
index 95dda5031f..5bdd3569c2 100644
--- a/src/common/platform/win32/i_mainwindow.cpp
+++ b/src/common/platform/win32/i_mainwindow.cpp
@@ -128,6 +128,11 @@ void MainWindow::HideNetStartPane()
 	NetStartWindow::HideNetStartPane();
 }
 
+void MainWindow::CloseNetStartPane()
+{
+	NetStartWindow::NetClose();
+}
+
 void MainWindow::SetNetStartProgress(int pos)
 {
 	NetStartWindow::SetNetStartProgress(pos);
diff --git a/src/common/platform/win32/i_mainwindow.h b/src/common/platform/win32/i_mainwindow.h
index 3c0c7e55df..83567135cf 100644
--- a/src/common/platform/win32/i_mainwindow.h
+++ b/src/common/platform/win32/i_mainwindow.h
@@ -29,6 +29,7 @@ public:
 	void SetNetStartProgress(int pos);
 	bool RunMessageLoop(bool (*timer_callback)(void*), void* userdata);
 	void HideNetStartPane();
+	void CloseNetStartPane();
 
 	void SetWindowTitle(const char* caption);
 
diff --git a/src/common/platform/win32/st_start.cpp b/src/common/platform/win32/st_start.cpp
index 8bc48d26e5..fceeb3cede 100644
--- a/src/common/platform/win32/st_start.cpp
+++ b/src/common/platform/win32/st_start.cpp
@@ -201,3 +201,8 @@ bool FBasicStartupScreen::NetLoop(bool (*timer_callback)(void *), void *userdata
 {
 	return mainwindow.RunMessageLoop(timer_callback, userdata);
 }
+
+void FBasicStartupScreen::NetClose()
+{
+	mainwindow.CloseNetStartPane();
+}
diff --git a/src/common/widgets/netstartwindow.cpp b/src/common/widgets/netstartwindow.cpp
index 69c83e5654..887f9cc316 100644
--- a/src/common/widgets/netstartwindow.cpp
+++ b/src/common/widgets/netstartwindow.cpp
@@ -64,6 +64,12 @@ bool NetStartWindow::RunMessageLoop(bool (*newtimer_callback)(void*), void* newu
 	return Instance->exitreason;
 }
 
+void NetStartWindow::NetClose()
+{
+	if (Instance != nullptr)
+		Instance->OnClose();
+}
+
 NetStartWindow::NetStartWindow() : Widget(nullptr, WidgetType::Window)
 {
 	SetWindowBackground(Colorf::fromRgba8(51, 51, 51));
diff --git a/src/common/widgets/netstartwindow.h b/src/common/widgets/netstartwindow.h
index 5d27b8ebfc..dcc9d688ea 100644
--- a/src/common/widgets/netstartwindow.h
+++ b/src/common/widgets/netstartwindow.h
@@ -14,6 +14,7 @@ public:
 	static void HideNetStartPane();
 	static void SetNetStartProgress(int pos);
 	static bool RunMessageLoop(bool (*timer_callback)(void*), void* userdata);
+	static void NetClose();
 
 private:
 	NetStartWindow();