Version 4.1

README.md

@@ -1,4 +1,4 @@
-# Moonlight Internet Streaming Helper
+# Moonlight Internet Hosting Tool
 * Enable Moonlight streaming from your PC over the Internet with no configuration required
 * Troubleshoot streaming issues with the included testing tool
 
@@ -8,5 +8,6 @@
 
 # Technical Features
 - Supports all major port forwarding protocols (UPnP, NAT-PMP, and PCP) for the best possible router compatibility
+- Supports streaming on IPv4-only, IPv6-only, and dual-stack Internet connections
 - Supports successful forwarding in double-NAT environments by configuring port mappings on all NATs found on the way to the Internet
 - Supports forwarding on Carrier-Grade NATs (CGNs) by directly using PCP when the ISP doesn't implement UPnP-PCP interoperability

mish-setup/Bundle.wxs

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Wix xmlns="http://schemas.microsoft.com/wix/2006/wi"
      xmlns:bal="http://schemas.microsoft.com/wix/BalExtension">
-	<Bundle Name="Moonlight Internet Streaming Helper" Manufacturer="Moonlight Game Streaming Project" Version="!(bind.packageVersion.mish)" UpgradeCode="a2ce5056-1114-44b9-b79b-952ef46d3d50">
+	<Bundle Name="Moonlight Internet Hosting Tool" Manufacturer="Moonlight Game Streaming Project" Version="!(bind.packageVersion.mish)" UpgradeCode="a2ce5056-1114-44b9-b79b-952ef46d3d50">
     <BootstrapperApplicationRef Id="WixStandardBootstrapperApplication.RtfLicense">
       <bal:WixStandardBootstrapperApplication
             LicenseFile="license.rtf"

mish-setup/mish-setup.wixproj

@@ -6,7 +6,7 @@
     <ProductVersion>3.10</ProductVersion>
     <ProjectGuid>a2ce5056-1114-44b9-b79b-952ef46d3d50</ProjectGuid>
     <SchemaVersion>2.0</SchemaVersion>
-    <OutputName>mish_setup</OutputName>
+    <OutputName>InternetHostingToolSetup</OutputName>
     <OutputType>Bundle</OutputType>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|x86' ">

mish/Product.wxs

@@ -2,7 +2,7 @@
 <Wix xmlns="http://schemas.microsoft.com/wix/2006/wi"
      xmlns:fire="http://schemas.microsoft.com/wix/FirewallExtension"
      xmlns:util="http://schemas.microsoft.com/wix/UtilExtension">
-  <Product Id="*" Name="Moonlight Internet Streaming Helper" Language="1033" Version="!(bind.fileVersion.MistExe)"
+  <Product Id="*" Name="Moonlight Internet Hosting Tool" Language="1033" Version="!(bind.fileVersion.MistExe)"
            Manufacturer="Moonlight Game Streaming Project" UpgradeCode="cfc2fb53-88e2-4867-851d-9ed9fe7ab2a3">
     <Package InstallerVersion="500" Compressed="yes" InstallScope="perMachine" />
 
@@ -17,10 +17,10 @@
   <Fragment>
     <Directory Id="TARGETDIR" Name="SourceDir">
       <Directory Id="ProgramFilesFolder">
-        <Directory Id="INSTALLFOLDER" Name="Moonlight Internet Streaming Helper" />
+        <Directory Id="INSTALLFOLDER" Name="Moonlight Internet Hosting Tool" />
       </Directory>
       <Directory Id="ProgramMenuFolder">
-        <Directory Id="ApplicationProgramsFolder" Name="Moonlight Internet Streaming Helper" />
+        <Directory Id="ApplicationProgramsFolder" Name="Moonlight Internet Hosting Tool" />
       </Directory>
       <Directory Id="CommonAppDataFolder">
         <Directory Name="MISS" Id="MISSLogFolder" />

miss/miss.cpp

@@ -97,7 +97,7 @@ bool UPnPMapPort(struct UPNPUrls* urls, struct IGDdatas* data, int proto, const
         printf("NOT FOUND" NL);
     }
     else if (err == UPNPCOMMAND_SUCCESS) {
-		// Some routers change the description, so we can't check that here
+        // Some routers change the description, so we can't check that here
         if (!strcmp(intClient, myAddr)) {
             if (atoi(leaseDuration) == 0) {
                 printf("OK (Permanent)" NL);
@@ -747,18 +747,18 @@ void ResetLogFile()
 {
     char oldLogFilePath[MAX_PATH + 1];
     char currentLogFilePath[MAX_PATH + 1];
-	char timeString[MAX_PATH + 1] = {};
+    char timeString[MAX_PATH + 1] = {};
-	SYSTEMTIME time;
+    SYSTEMTIME time;
 
     ExpandEnvironmentStringsA("%ProgramData%\\MISS\\miss-old.log", oldLogFilePath, sizeof(oldLogFilePath));
     ExpandEnvironmentStringsA("%ProgramData%\\MISS\\miss-current.log", currentLogFilePath, sizeof(currentLogFilePath));
 
-	// Close the existing stdout handle. This is important because otherwise
+    // Close the existing stdout handle. This is important because otherwise
-	// it may still be open as stdout when we try to MoveFileEx below.
+    // it may still be open as stdout when we try to MoveFileEx below.
-	fclose(stdout);
+    fclose(stdout);
 
-	// Rotate the current to the old log file
+    // Rotate the current to the old log file
-	MoveFileExA(currentLogFilePath, oldLogFilePath, MOVEFILE_REPLACE_EXISTING);
+    MoveFileExA(currentLogFilePath, oldLogFilePath, MOVEFILE_REPLACE_EXISTING);
 
     // Redirect stdout to this new file
     freopen(currentLogFilePath, "w", stdout);
@@ -766,10 +766,10 @@ void ResetLogFile()
     // Print a log header
     printf("Moonlight Internet Streaming Service v" VER_VERSION_STR NL);
 
-	// Print the current time
+    // Print the current time
-	GetSystemTime(&time);
+    GetSystemTime(&time);
-	GetTimeFormatA(LOCALE_SYSTEM_DEFAULT, 0, &time, "hh':'mm':'ss tt", timeString, ARRAYSIZE(timeString));
+    GetTimeFormatA(LOCALE_SYSTEM_DEFAULT, 0, &time, "hh':'mm':'ss tt", timeString, ARRAYSIZE(timeString));
-	printf("The current UTC time is: %s" NL, timeString);
+    printf("The current UTC time is: %s" NL, timeString);
 }
 
 DWORD WINAPI GameStreamStateChangeThread(PVOID Context)

mist/mist.cpp

@@ -1,11 +1,5 @@
-#define _CRT_RAND_S
+#include "mist.h"
-#define _CRT_SECURE_NO_WARNINGS
-#include <stdlib.h>
 
-#define WIN32_LEAN_AND_MEAN
-#define _WINSOCK_DEPRECATED_NO_WARNINGS
-#include <Windows.h>
-#include <WinSock2.h>
 #include <Ws2tcpip.h>
 #include <stdio.h>
 #include <assert.h>
@@ -13,8 +7,6 @@
 #include <objbase.h>
 #include <WinInet.h>
 
-#include "..\version.h"
-
 #pragma comment(lib, "miniupnpc.lib")
 #pragma comment(lib, "libnatpmp.lib")
 #pragma comment(lib, "ws2_32.lib")
@@ -29,8 +21,6 @@
 #define NATPMP_STATICLIB
 #include <natpmp.h>
 
-bool getExternalAddressPortIP4(int proto, unsigned short localPort, PSOCKADDR_IN wanAddr);
-
 static struct port_entry {
     int proto;
     int port;
@@ -44,8 +34,8 @@ static struct port_entry {
     {IPPROTO_UDP, 48000, true},
 
 #if 0
-	// These are not currently used, so let's
+    // These are not currently used, so let's
-	// avoid testing them for now.
+    // avoid testing them for now.
     {IPPROTO_UDP, 48002, true},
     {IPPROTO_UDP, 48010, true}
 #endif
@@ -74,13 +64,14 @@ VOID CALLBACK MsgBoxHelpCallback(LPHELPINFO lpHelpInfo)
 
 void DisplayMessage(const char* message, const char* helpUrl = nullptr, MessagePriority priority = MpError, bool terminal = true)
 {
-    printf("%s\n", message);
+    fprintf(CONSOLE_OUT, "%s\n", message);
+    fprintf(LOG_OUT, "%s\n", message);
 
     if (terminal) {
-		char logPath[MAX_PATH + 1];
+        char logPath[MAX_PATH + 1];
-		FILE* f;
+        FILE* f;
 
-        printf("--------------- CURRENT MISS LOG -------------------\n");
+        fprintf(LOG_OUT, "--------------- CURRENT MISS LOG -------------------\n");
 
         ExpandEnvironmentStringsA("%ProgramData%\\MISS\\miss-current.log", logPath, sizeof(logPath));
         f = fopen(logPath, "r");
@@ -88,63 +79,63 @@ void DisplayMessage(const char* message, const char* helpUrl = nullptr, MessageP
             char buffer[1024];
             while (!feof(f)) {
                 int bytesRead = fread(buffer, 1, ARRAYSIZE(buffer), f);
-                fwrite(buffer, 1, bytesRead, stdout);
+                fwrite(buffer, 1, bytesRead, LOG_OUT);
             }
             fclose(f);
         }
         else {
-            printf("Failed to find current MISS log\n");
+            fprintf(LOG_OUT, "Failed to find current MISS log\n");
         }
 
-		printf("\n----------------- OLD MISS LOG ---------------------\n");
+        fprintf(LOG_OUT, "\n----------------- OLD MISS LOG ---------------------\n");
 
-		ExpandEnvironmentStringsA("%ProgramData%\\MISS\\miss-old.log", logPath, sizeof(logPath));
+        ExpandEnvironmentStringsA("%ProgramData%\\MISS\\miss-old.log", logPath, sizeof(logPath));
-		f = fopen(logPath, "r");
+        f = fopen(logPath, "r");
-		if (f != nullptr) {
+        if (f != nullptr) {
-			char buffer[1024];
+            char buffer[1024];
-			while (!feof(f)) {
+            while (!feof(f)) {
-				int bytesRead = fread(buffer, 1, ARRAYSIZE(buffer), f);
+                int bytesRead = fread(buffer, 1, ARRAYSIZE(buffer), f);
-				fwrite(buffer, 1, bytesRead, stdout);
+                fwrite(buffer, 1, bytesRead, LOG_OUT);
-			}
+            }
-			fclose(f);
+            fclose(f);
-		}
+        }
-		else {
+        else {
-			printf("Failed to find old MISS log\n");
+            fprintf(LOG_OUT, "Failed to find old MISS log\n");
-		}
+        }
 
-		printf("--------------- CURRENT GSV6FWD LOG -------------------\n");
+        fprintf(LOG_OUT, "--------------- CURRENT GSV6FWD LOG -------------------\n");
 
-		ExpandEnvironmentStringsA("%ProgramData%\\MISS\\GSv6Fwd-current.log", logPath, sizeof(logPath));
+        ExpandEnvironmentStringsA("%ProgramData%\\MISS\\GSv6Fwd-current.log", logPath, sizeof(logPath));
-		f = fopen(logPath, "r");
+        f = fopen(logPath, "r");
-		if (f != nullptr) {
+        if (f != nullptr) {
-			char buffer[1024];
+            char buffer[1024];
-			while (!feof(f)) {
+            while (!feof(f)) {
-				int bytesRead = fread(buffer, 1, ARRAYSIZE(buffer), f);
+                int bytesRead = fread(buffer, 1, ARRAYSIZE(buffer), f);
-				fwrite(buffer, 1, bytesRead, stdout);
+                fwrite(buffer, 1, bytesRead, LOG_OUT);
-			}
+            }
-			fclose(f);
+            fclose(f);
-		}
+        }
-		else {
+        else {
-			printf("Failed to find current GSv6Fwd log\n");
+            fprintf(LOG_OUT, "Failed to find current GSv6Fwd log\n");
-		}
+        }
 
-		printf("\n----------------- OLD GSV6FWD LOG ---------------------\n");
+        fprintf(LOG_OUT, "\n----------------- OLD GSV6FWD LOG ---------------------\n");
 
-		ExpandEnvironmentStringsA("%ProgramData%\\MISS\\GSv6Fwd-old.log", logPath, sizeof(logPath));
+        ExpandEnvironmentStringsA("%ProgramData%\\MISS\\GSv6Fwd-old.log", logPath, sizeof(logPath));
-		f = fopen(logPath, "r");
+        f = fopen(logPath, "r");
-		if (f != nullptr) {
+        if (f != nullptr) {
-			char buffer[1024];
+            char buffer[1024];
-			while (!feof(f)) {
+            while (!feof(f)) {
-				int bytesRead = fread(buffer, 1, ARRAYSIZE(buffer), f);
+                int bytesRead = fread(buffer, 1, ARRAYSIZE(buffer), f);
-				fwrite(buffer, 1, bytesRead, stdout);
+                fwrite(buffer, 1, bytesRead, LOG_OUT);
-			}
+            }
-			fclose(f);
+            fclose(f);
-		}
+        }
-		else {
+        else {
-			printf("Failed to find old GSv6Fwd log\n");
+            fprintf(LOG_OUT, "Failed to find old GSv6Fwd log\n");
-		}
+        }
 
-        fflush(stdout);
+        fflush(LOG_OUT);
     }
 
     MSGBOXPARAMSA msgParams;
@@ -175,7 +166,7 @@ void DisplayMessage(const char* message, const char* helpUrl = nullptr, MessageP
 
     if (priority != MpInfo && terminal) {
         UINT flags = MB_YESNO | MB_TOPMOST | MB_SETFOREGROUND | MB_ICONINFORMATION;
-        switch (MessageBoxA(nullptr, "Would you like to view the troubleshooting log?",
+        switch (MessageBoxA(nullptr, "Would you like to view the troubleshooting log?\n\nYou will need to provide this log if you ask for help on the Moonlight Discord server.",
             "Moonlight Internet Streaming Tester", flags))
         {
         case IDYES:
@@ -196,7 +187,7 @@ bool IsGameStreamEnabled()
 
     error = RegOpenKeyExA(HKEY_LOCAL_MACHINE, "Software\\NVIDIA Corporation\\NvStream", 0, KEY_READ | KEY_WOW64_64KEY, &key);
     if (error != ERROR_SUCCESS) {
-        printf("RegOpenKeyEx() failed: %d\n", error);
+        fprintf(LOG_OUT, "RegOpenKeyEx() failed: %d\n", error);
         DisplayMessage("GeForce Experience was not detected on this PC. Make sure you're installing this utility on your GeForce GameStream-compatible PC, not the device running Moonlight.",
             "https://github.com/moonlight-stream/moonlight-docs/wiki/Setup-Guide");
         return false;
@@ -208,14 +199,14 @@ bool IsGameStreamEnabled()
     if (error != ERROR_SUCCESS || !enabled) {
         // GFE may not even write EnableStreaming until the user enables GameStream for the first time
         if (error != ERROR_SUCCESS) {
-            printf("RegQueryValueExA() failed: %d\n", error);
+            fprintf(LOG_OUT, "RegQueryValueExA() failed: %d\n", error);
         }
         DisplayMessage("GameStream is not enabled in GeForce Experience. Please open GeForce Experience settings, navigate to the Shield tab, and turn GameStream on.",
             "https://github.com/moonlight-stream/moonlight-docs/wiki/Setup-Guide");
         return false;
     }
     else {
-        printf("GeForce Experience installed and GameStream is enabled\n");
+        fprintf(LOG_OUT, "GeForce Experience installed and GameStream is enabled\n");
         return true;
     }
 }
@@ -225,21 +216,23 @@ enum PortTestStatus {
     PortTestError,
     PortTestUnknown
 };
-PortTestStatus TestPort(PSOCKADDR_STORAGE addr, int proto, int port, bool withServer)
+PortTestStatus TestPort(PSOCKADDR_STORAGE addr, int proto, int port, bool withServer, bool isLoopbackRelay)
 {
     SOCKET clientSock = INVALID_SOCKET, serverSock = INVALID_SOCKET;
     int err;
 
     clientSock = socket(addr->ss_family, proto == IPPROTO_TCP ? SOCK_STREAM : SOCK_DGRAM, proto);
     if (clientSock == INVALID_SOCKET) {
-        printf("socket() failed: %d\n", WSAGetLastError());
+        fprintf(LOG_OUT, "socket() failed: %d\n", WSAGetLastError());
         return PortTestError;
     }
 
     if (withServer) {
-        serverSock = socket(addr->ss_family, proto == IPPROTO_TCP ? SOCK_STREAM : SOCK_DGRAM, proto);
+        // Even if we are testing IPv6, our server socket should still be on IPv4 to allow the
+        // IPv6 relay to do its job (since it's already bound to all GFE ports on v6)
+        serverSock = socket(AF_INET, proto == IPPROTO_TCP ? SOCK_STREAM : SOCK_DGRAM, proto);
         if (serverSock == INVALID_SOCKET) {
-            printf("socket() failed: %d\n", WSAGetLastError());
+            fprintf(LOG_OUT, "socket() failed: %d\n", WSAGetLastError());
             closesocket(clientSock);
             return PortTestError;
         }
@@ -251,21 +244,22 @@ PortTestStatus TestPort(PSOCKADDR_STORAGE addr, int proto, int port, bool withSe
         if (err == SOCKET_ERROR) {
             if (WSAGetLastError() == WSAEADDRINUSE) {
                 // If someone is already listening (perhaps GFE is currently streaming),
-                // we can proceed if it's a TCP connection.
+                // we can proceed if it's a TCP connection unless it's a loopback relay
-                if (proto == IPPROTO_TCP) {
+                // which would give us a false positive result.
+                if (proto == IPPROTO_TCP && !isLoopbackRelay) {
                     closesocket(serverSock);
                     serverSock = INVALID_SOCKET;
                 }
                 else {
                     // We can't continue to test for UDP ports.
-                    printf("Unknown (in use)\n");
+                    fprintf(LOG_OUT, "Unknown (in use)\n");
                     closesocket(clientSock);
                     closesocket(serverSock);
                     return PortTestUnknown;
                 }
             }
             else {
-                printf("bind() failed: %d\n", WSAGetLastError());
+                fprintf(LOG_OUT, "bind() failed: %d\n", WSAGetLastError());
                 closesocket(clientSock);
                 closesocket(serverSock);
                 return PortTestError;
@@ -275,7 +269,7 @@ PortTestStatus TestPort(PSOCKADDR_STORAGE addr, int proto, int port, bool withSe
         if (proto == IPPROTO_TCP && serverSock != INVALID_SOCKET) {
             err = listen(serverSock, 1);
             if (err == SOCKET_ERROR) {
-                printf("listen() failed: %d\n", WSAGetLastError());
+                fprintf(LOG_OUT, "listen() failed: %d\n", WSAGetLastError());
                 closesocket(clientSock);
                 closesocket(serverSock);
                 return PortTestError;
@@ -286,7 +280,7 @@ PortTestStatus TestPort(PSOCKADDR_STORAGE addr, int proto, int port, bool withSe
     ULONG nbIo = 1;
     err = ioctlsocket(clientSock, FIONBIO, &nbIo);
     if (err == SOCKET_ERROR) {
-        printf("ioctlsocket() failed: %d\n", WSAGetLastError());
+        fprintf(LOG_OUT, "ioctlsocket() failed: %d\n", WSAGetLastError());
         closesocket(clientSock);
         if (serverSock != INVALID_SOCKET) {
             closesocket(serverSock);
@@ -304,7 +298,7 @@ PortTestStatus TestPort(PSOCKADDR_STORAGE addr, int proto, int port, bool withSe
     if (proto == IPPROTO_TCP) {
         err = connect(clientSock, (struct sockaddr*)&sin6, addrLen);
         if (err == SOCKET_ERROR && WSAGetLastError() != WSAEWOULDBLOCK) {
-            printf("connect() failed: %d\n", WSAGetLastError());
+            fprintf(LOG_OUT, "connect() failed: %d\n", WSAGetLastError());
         }
         else {
             struct timeval timeout = {};
@@ -312,30 +306,30 @@ PortTestStatus TestPort(PSOCKADDR_STORAGE addr, int proto, int port, bool withSe
 
             FD_ZERO(&fds);
 
-			if (serverSock != INVALID_SOCKET) {
+            if (serverSock != INVALID_SOCKET) {
-				FD_SET(serverSock, &fds);
+                FD_SET(serverSock, &fds);
-			}
+            }
-			else {
+            else {
-				FD_SET(clientSock, &fds);
+                FD_SET(clientSock, &fds);
-			}
+            }
 
-			// If we have a server socket, listen for the accept() instead of the
+            // If we have a server socket, listen for the accept() instead of the
-			// connect() so we can be compatible with the loopback relay.
+            // connect() so we can be compatible with the loopback relay.
             timeout.tv_sec = 3;
             err = select(0,
-				serverSock != INVALID_SOCKET ? &fds : nullptr,
+                serverSock != INVALID_SOCKET ? &fds : nullptr,
-				serverSock == INVALID_SOCKET ? &fds : nullptr,
+                serverSock == INVALID_SOCKET ? &fds : nullptr,
-				nullptr, &timeout);
+                nullptr, &timeout);
             if (err == 1) {
                 // Our FD was signalled for connect() or accept() completion
-                printf("Success\n");
+                fprintf(LOG_OUT, "Success\n");
             }
             else if (err == 0) {
                 // Timed out
-                printf("Timeout\n");
+                fprintf(LOG_OUT, "Timeout\n");
             }
             else {
-                printf("select() failed: %d\n", WSAGetLastError());
+                fprintf(LOG_OUT, "select() failed: %d\n", WSAGetLastError());
             }
         }
 
@@ -348,12 +342,18 @@ PortTestStatus TestPort(PSOCKADDR_STORAGE addr, int proto, int port, bool withSe
     }
     else {
         const char testMsg[] = "moonlight-test";
-        err = sendto(clientSock, testMsg, sizeof(testMsg), 0, (struct sockaddr*)&sin6, addrLen);
+
-        if (err == SOCKET_ERROR) {
+        // Send several test packets to ensure a random lost packet doesn't make the test fail
-            printf("sendto() failed: %d\n", WSAGetLastError());
+        for (int i = 0; i < 5; i++) {
-            closesocket(clientSock);
+            err = sendto(clientSock, testMsg, sizeof(testMsg), 0, (struct sockaddr*)&sin6, addrLen);
-            closesocket(serverSock);
+            if (err == SOCKET_ERROR) {
-            return PortTestError;
+                fprintf(LOG_OUT, "sendto() failed: %d\n", WSAGetLastError());
+                closesocket(clientSock);
+                closesocket(serverSock);
+                return PortTestError;
+            }
+
+            Sleep(200);
         }
 
         struct timeval timeout = {};
@@ -362,18 +362,18 @@ PortTestStatus TestPort(PSOCKADDR_STORAGE addr, int proto, int port, bool withSe
         FD_ZERO(&fds);
         FD_SET(serverSock, &fds);
 
-        timeout.tv_sec = 3;
+        timeout.tv_sec = 2;
         err = select(0, &fds, nullptr, nullptr, &timeout);
         if (err == 1) {
             // Our FD was signalled for data available
-            printf("Success\n");
+            fprintf(LOG_OUT, "Success\n");
         }
         else if (err == 0) {
             // Timed out
-            printf("Timeout\n");
+            fprintf(LOG_OUT, "Timeout\n");
         }
         else {
-            printf("select() failed: %d\n", WSAGetLastError());
+            fprintf(LOG_OUT, "select() failed: %d\n", WSAGetLastError());
         }
 
         closesocket(clientSock);
@@ -385,138 +385,171 @@ PortTestStatus TestPort(PSOCKADDR_STORAGE addr, int proto, int port, bool withSe
 
 PortTestStatus TestHttpPort(PSOCKADDR_STORAGE addr, int port)
 {
-	HINTERNET hInternet;
+    HINTERNET hInternet;
-	HINTERNET hRequest;
+    HINTERNET hRequest;
-	char url[1024];
+    char url[1024];
 
-	hInternet = InternetOpenA("MIST", 0, nullptr, nullptr, 0);
+    hInternet = InternetOpenA("MIST", 0, nullptr, nullptr, 0);
-	if (hInternet == nullptr) {
+    if (hInternet == nullptr) {
-		printf("InternetOpen() failed: %d\n", GetLastError());
+        fprintf(LOG_OUT, "InternetOpen() failed: %d\n", GetLastError());
-		return PortTestError;
+        return PortTestError;
-	}
+    }
 
-	char addrStr[64];
+    char addrStr[INET6_ADDRSTRLEN + 2];
-	inet_ntop(AF_INET, &((struct sockaddr_in*)addr)->sin_addr, addrStr, sizeof(addrStr));
+    if (addr->ss_family == AF_INET) {
+        inet_ntop(AF_INET, &((struct sockaddr_in*)addr)->sin_addr, addrStr, sizeof(addrStr));
+    }
+    else {
+        // The address string must be escaped for usage in URLs
+        addrStr[0] = '[';
+        inet_ntop(AF_INET6, &((struct sockaddr_in6*)addr)->sin6_addr, &addrStr[1], INET6_ADDRSTRLEN);
+        strcat_s(addrStr, "]");
+    }
 
-	sprintf(url, "%s://%s:%d/",
+    sprintf(url, "%s://%s:%d/",
-		port == 47989 ? "http" : "https",
+        port == 47989 ? "http" : "https",
-		addrStr,
+        addrStr,
-		port);
+        port);
 
-	hRequest = InternetOpenUrlA(hInternet, url, nullptr, 0,
+    hRequest = InternetOpenUrlA(hInternet, url, nullptr, 0,
-		INTERNET_FLAG_IGNORE_CERT_DATE_INVALID | INTERNET_FLAG_NO_UI | INTERNET_FLAG_NO_AUTH | INTERNET_FLAG_NO_COOKIES | INTERNET_FLAG_RELOAD,
+        INTERNET_FLAG_IGNORE_CERT_DATE_INVALID | INTERNET_FLAG_NO_UI | INTERNET_FLAG_NO_AUTH | INTERNET_FLAG_NO_COOKIES | INTERNET_FLAG_RELOAD,
-		NULL);
+        NULL);
-	if (hRequest == nullptr) {
+    if (hRequest == nullptr) {
-		if (GetLastError() == ERROR_INTERNET_CLIENT_AUTH_CERT_NEEDED) {
+        if (GetLastError() == ERROR_INTERNET_CLIENT_AUTH_CERT_NEEDED) {
-			// This is expected for our HTTPS connection
+            // This is expected for our HTTPS connection
-			printf("Success\n");
+            fprintf(LOG_OUT, "Success\n");
-		}
+        }
-		else {
+        else {
-			// CANNOT_CONNECT is the "expected" error
+            // CANNOT_CONNECT is the "expected" error
-			if (GetLastError() == ERROR_INTERNET_CANNOT_CONNECT) {
+            if (GetLastError() == ERROR_INTERNET_CANNOT_CONNECT) {
-				printf("Failed\n");
+                fprintf(LOG_OUT, "Failed\n");
-			}
+            }
-			else {
+            else {
-				printf("Failed: %d\n", GetLastError());
+                fprintf(LOG_OUT, "Failed: %d\n", GetLastError());
-			}
+            }
 
-			InternetCloseHandle(hInternet);
+            InternetCloseHandle(hInternet);
-			return PortTestError;
+            return PortTestError;
-		}
+        }
-	}
+    }
-	else {
+    else {
-		printf("Success\n");
+        fprintf(LOG_OUT, "Success\n");
-		InternetCloseHandle(hRequest);
+        InternetCloseHandle(hRequest);
-	}
+    }
 
 
-	InternetCloseHandle(hInternet);
+    InternetCloseHandle(hInternet);
 
-	return PortTestOk;
+    return PortTestOk;
 }
 
-bool TestAllPorts(PSOCKADDR_STORAGE addr, char* portMsg, int portMsgLen)
+bool TestAllPorts(PSOCKADDR_STORAGE addr, char* portMsg, int portMsgLen, bool isLoopbackRelay, bool consolePrint, bool* allPortsFailed = nullptr)
 {
     bool ret = true;
 
+    if (allPortsFailed) {
+        *allPortsFailed = true;
+    }
+
     for (int i = 0; i < ARRAYSIZE(k_Ports); i++) {
-        printf("Testing %s %d...",
+        fprintf(LOG_OUT, "Testing %s %d...",
             k_Ports[i].proto == IPPROTO_TCP ? "TCP" : "UDP",
             k_Ports[i].port);
-		PortTestStatus status;
-		
-		status = TestPort(addr, k_Ports[i].proto, k_Ports[i].port, k_Ports[i].withServer);
 
-		if (status != PortTestError && !k_Ports[i].withServer) {
+        if (consolePrint) {
-			// Test using a real HTTP client if the port wasn't totally dead.
+            fprintf(CONSOLE_OUT, "\tTesting %s %d...\n",
-			// This is required to confirm functionality with the loopback relay.
+                k_Ports[i].proto == IPPROTO_TCP ? "TCP" : "UDP",
-			// TestHttpPort() can take significantly longer to timeout than TestPort(),
+                k_Ports[i].port);
-			// so we only do this test if we believe we're likely to get a response.
+        }
-			printf("Testing TCP %d with HTTP traffic...", k_Ports[i].port);
+
-			status = TestHttpPort(addr, k_Ports[i].port);
+        PortTestStatus status = TestPort(addr, k_Ports[i].proto, k_Ports[i].port, k_Ports[i].withServer, isLoopbackRelay);
-		}
+
+        if (status != PortTestError && !k_Ports[i].withServer) {
+            // Test using a real HTTP client if the port wasn't totally dead.
+            // This is required to confirm functionality with the loopback relay.
+            // TestHttpPort() can take significantly longer to timeout than TestPort(),
+            // so we only do this test if we believe we're likely to get a response.
+            fprintf(LOG_OUT, "Testing TCP %d with HTTP traffic...", k_Ports[i].port);
+            status = TestHttpPort(addr, k_Ports[i].port);
+        }
 
         if (status != PortTestOk) {
             // If we got an unknown result, assume it matches with whatever
             // we've gotten so far.
             if (status == PortTestError || !ret) {
-                int msgLen = snprintf(portMsg, portMsgLen, "%s %d\n",
+                if (portMsg != NULL && portMsgLen > 0) {
-                    k_Ports[i].proto == IPPROTO_TCP ? "TCP" : "UDP",
+                    int msgLen = snprintf(portMsg, portMsgLen, "%s %d\n",
-                    k_Ports[i].port);
+                        k_Ports[i].proto == IPPROTO_TCP ? "TCP" : "UDP",
-                portMsg += msgLen;
+                        k_Ports[i].port);
-                portMsgLen -= msgLen;
+                    portMsg += msgLen;
+                    portMsgLen -= msgLen;
+                }
 
                 // Keep going to check all ports and report the failing ones
                 ret = false;
             }
         }
+        else if (allPortsFailed) {
+            *allPortsFailed = false;
+        }
     }
 
     return ret;
 }
 
-bool FindLocalInterfaceIP4Address(PSOCKADDR_IN addr)
+bool FindLocalInterfaceIPAddress(int family, PSOCKADDR_STORAGE addr)
 {
     SOCKET s;
-    struct hostent* host;
+    struct addrinfo hint = {};
+    struct addrinfo* result;
+    int err;
 
-    printf("Finding local IP address...");
+    fprintf(LOG_OUT, "Finding local %s address...", family == AF_INET ? "IPv4" : "IPv6");
 
-    host = gethostbyname("moonlight-stream.org");
+    hint.ai_family = family;
-    if (host == nullptr) {
+    hint.ai_socktype = SOCK_STREAM;
-        printf("gethostbyname() failed: %d\n", WSAGetLastError());
+    hint.ai_protocol = IPPROTO_TCP;
+    hint.ai_flags = AI_ADDRCONFIG;
+    err = getaddrinfo("moonlight-stream.org", "https", &hint, &result);
+    if (err != 0 || result == NULL) {
+        fprintf(LOG_OUT, "getaddrinfo() failed: %d\n", err);
         return false;
     }
 
-    s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
+    s = socket(result->ai_family, result->ai_socktype, result->ai_protocol);
     if (s == INVALID_SOCKET) {
-        printf("socket() failed: %d\n", WSAGetLastError());
+        fprintf(LOG_OUT, "socket() failed: %d\n", WSAGetLastError());
+        freeaddrinfo(result);
         return false;
     }
 
-    SOCKADDR_IN sin = {};
+    err = connect(s, (struct sockaddr*)result->ai_addr, result->ai_addrlen);
-    sin.sin_family = AF_INET;
-    sin.sin_port = htons(443);
-    sin.sin_addr = *(struct in_addr*)host->h_addr;
-    int err = connect(s, (struct sockaddr*)&sin, sizeof(sin));
     if (err == SOCKET_ERROR) {
-        printf("connect() failed: %d\n", WSAGetLastError());
+        fprintf(LOG_OUT, "connect() failed: %d\n", WSAGetLastError());
         closesocket(s);
+        freeaddrinfo(result);
         return false;
     }
 
+    freeaddrinfo(result);
+
     // Determine which local interface we bound to
     int nameLen = sizeof(*addr);
     err = getsockname(s, (struct sockaddr*)addr, &nameLen);
     if (err == SOCKET_ERROR) {
-        printf("getsockname() failed: %d\n", WSAGetLastError());
+        fprintf(LOG_OUT, "getsockname() failed: %d\n", WSAGetLastError());
         closesocket(s);
         return false;
     }
 
-    char addrStr[64];
+    char addrStr[INET6_ADDRSTRLEN];
-    inet_ntop(AF_INET, &addr->sin_addr, addrStr, sizeof(addrStr));
+    if (addr->ss_family == AF_INET) {
-    printf("%s\n", addrStr);
+        inet_ntop(AF_INET, &((struct sockaddr_in*)addr)->sin_addr, addrStr, sizeof(addrStr));
+    }
+    else {
+        inet_ntop(AF_INET6, &((struct sockaddr_in6*)addr)->sin6_addr, addrStr, sizeof(addrStr));
+    }
+    fprintf(LOG_OUT, "%s\n", addrStr);
 
     return true;
 }
@@ -551,28 +584,28 @@ UPnPPortStatus UPnPCheckPort(struct UPNPUrls* urls, struct IGDdatas* data, int p
         return ERRORED;
     }
 
-    printf("Checking for UPnP port mapping for %s %s -> %s...", protoStr, portStr, myAddr);
+    fprintf(LOG_OUT, "Checking for UPnP port mapping for %s %s -> %s...", protoStr, portStr, myAddr);
     int err = UPNP_GetSpecificPortMappingEntry(
         urls->controlURL, data->first.servicetype, portStr, protoStr, nullptr,
         intClient, intPort, desc, enabled, leaseDuration);
     if (err == 714) {
         // NoSuchEntryInArray
-        printf("NOT FOUND\n");
+        fprintf(LOG_OUT, "NOT FOUND\n");
         return NOT_FOUND;
     }
     else if (err == UPNPCOMMAND_SUCCESS) {
         if (!strcmp(myAddr, intClient)) {
-            printf("OK\n");
+            fprintf(LOG_OUT, "OK\n");
             return OK;
         }
         else {
-            printf("CONFLICT - %s %s\n", desc, intClient);
+            fprintf(LOG_OUT, "CONFLICT - %s %s\n", desc, intClient);
             snprintf(conflictMessage, 128, "%s (%s)", desc, intClient);
             return CONFLICTED;
         }
     }
     else {
-        printf("ERROR %d\n", err);
+        fprintf(LOG_OUT, "ERROR %d\n", err);
         return ERRORED;
     }
 }
@@ -582,23 +615,27 @@ bool CheckWANAccess(PSOCKADDR_IN wanAddr, PSOCKADDR_IN reportedWanAddr, bool* fo
     natpmp_t natpmp;
     bool foundUpnpIgd = false;
 
+    wanAddr->sin_family = AF_INET;
+    reportedWanAddr->sin_family = AF_INET;
     *foundPortForwardingRules = false;
     *igdDisconnected = false;
 
     bool gotReportedWanAddress = false;
     int natPmpErr = initnatpmp(&natpmp, 0, 0);
     if (natPmpErr != 0) {
-        printf("initnatpmp() failed: %d\n", natPmpErr);
+        fprintf(LOG_OUT, "initnatpmp() failed: %d\n", natPmpErr);
     }
     else {
         natPmpErr = sendpublicaddressrequest(&natpmp);
         if (natPmpErr < 0) {
-            printf("sendpublicaddressrequest() failed: %d\n", natPmpErr);
+            fprintf(LOG_OUT, "sendpublicaddressrequest() failed: %d\n", natPmpErr);
             closenatpmp(&natpmp);
         }
     }
 
     {
+        fprintf(CONSOLE_OUT, "\tTesting UPnP...\n");
+
         int upnpErr;
         struct UPNPDev* ipv4Devs = upnpDiscoverAll(5000, nullptr, nullptr, UPNP_LOCAL_PORT_ANY, 0, 2, &upnpErr);
 
@@ -614,19 +651,19 @@ bool CheckWANAccess(PSOCKADDR_IN wanAddr, PSOCKADDR_IN reportedWanAddr, bool* fo
                 if (ret == 2) {
                     *igdDisconnected = true;
                 }
-                printf("Discovered UPnP IGD at: %s\n", urls.controlURL);
+                fprintf(LOG_OUT, "Discovered UPnP IGD at: %s\n", urls.controlURL);
-                printf("Detecting WAN IP address via UPnP...");
+                fprintf(LOG_OUT, "Detecting WAN IP address via UPnP...");
                 ret = UPNP_GetExternalIPAddress(urls.controlURL, data.first.servicetype, wanAddrStr);
                 if (ret == UPNPCOMMAND_SUCCESS && strlen(wanAddrStr) > 0) {
                     reportedWanAddr->sin_addr.S_un.S_addr = inet_addr(wanAddrStr);
-                    printf("%s\n", wanAddrStr);
+                    fprintf(LOG_OUT, "%s\n", wanAddrStr);
 
                     if (reportedWanAddr->sin_addr.S_un.S_addr != 0) {
                         gotReportedWanAddress = true;
                     }
                 }
                 else {
-                    printf("FAILED %d\n", ret);
+                    fprintf(LOG_OUT, "FAILED %d\n", ret);
                 }
 
                 char conflictMessage[512];
@@ -652,19 +689,21 @@ bool CheckWANAccess(PSOCKADDR_IN wanAddr, PSOCKADDR_IN reportedWanAddr, bool* fo
                 }
             }
             else {
-                printf("No UPnP IGD detected\n");
+                fprintf(LOG_OUT, "No UPnP IGD detected\n");
             }
 
             FreeUPNPUrls(&urls);
         }
         else {
-            printf("No UPnP devices detected\n");
+            fprintf(LOG_OUT, "No UPnP devices detected\n");
         }
     }
 
     // Use the delay of upnpDiscoverAll() to also allow the NAT-PMP endpoint time to respond
     if (natPmpErr >= 0) {
-        printf("Detecting WAN IP address via NAT-PMP...");
+        fprintf(CONSOLE_OUT, "\tTesting NAT-PMP...\n");
+
+        fprintf(LOG_OUT, "Detecting WAN IP address via NAT-PMP...");
 
         natpmpresp_t response;
         natPmpErr = readnatpmpresponseorretry(&natpmp, &response);
@@ -674,7 +713,7 @@ bool CheckWANAccess(PSOCKADDR_IN wanAddr, PSOCKADDR_IN reportedWanAddr, bool* fo
             char addrStr[64];
             reportedWanAddr->sin_addr = response.pnu.publicaddress.addr;
             inet_ntop(AF_INET, &response.pnu.publicaddress.addr, addrStr, sizeof(addrStr));
-            printf("%s\n", addrStr);
+            fprintf(LOG_OUT, "%s\n", addrStr);
             if (reportedWanAddr->sin_addr.S_un.S_addr != 0) {
                 gotReportedWanAddress = true;
                 
@@ -686,11 +725,13 @@ bool CheckWANAccess(PSOCKADDR_IN wanAddr, PSOCKADDR_IN reportedWanAddr, bool* fo
             }
         }
         else {
-            printf("FAILED %d\n", natPmpErr);
+            fprintf(LOG_OUT, "FAILED %d\n", natPmpErr);
         }
     }
 
-    printf("Detecting WAN IP address via STUN...");
+    fprintf(LOG_OUT, "Detecting WAN IP address via STUN...");
+    fprintf(CONSOLE_OUT, "\tTesting STUN...\n");
+
     if (!getExternalAddressPortIP4(IPPROTO_UDP, 0, wanAddr) && !getExternalAddressPortIP4(IPPROTO_TCP, 0, wanAddr)) {
         DisplayMessage("Unable to determine your public IP address. Please check your Internet connection or try again in a few minutes.");
         return false;
@@ -698,7 +739,7 @@ bool CheckWANAccess(PSOCKADDR_IN wanAddr, PSOCKADDR_IN reportedWanAddr, bool* fo
     else {
         char addrStr[64];
         inet_ntop(AF_INET, &wanAddr->sin_addr, addrStr, sizeof(addrStr));
-        printf("%s\n", addrStr);
+        fprintf(LOG_OUT, "%s\n", addrStr);
 
         if (!gotReportedWanAddress) {
             // If we didn't get anything from UPnP or NAT-PMP, just populate the reported
@@ -749,25 +790,25 @@ bool IsDoubleNAT(PSOCKADDR_IN wanAddr)
 int main(int argc, char* argv[])
 {
     WSADATA wsaData;
-	SYSTEMTIME time;
+    SYSTEMTIME time;
-	char timeString[MAX_PATH + 1] = {};
+    char timeString[MAX_PATH + 1] = {};
 
     char tempPath[MAX_PATH + 1];
     GetTempPathA(sizeof(tempPath), tempPath);
 
     snprintf(logFilePath, sizeof(logFilePath), "%s\\%s", tempPath, "mis-test.log");
-    freopen(logFilePath, "w", stdout);
+    freopen(logFilePath, "w", LOG_OUT);
 
     // Print a log header
-    printf("Moonlight Internet Streaming Tester v" VER_VERSION_STR "\n");
+    fprintf(LOG_OUT, "Moonlight Internet Streaming Tester v" VER_VERSION_STR "\n");
 
-	// Print the current time
+    // Print the current time
-	GetSystemTime(&time);
+    GetSystemTime(&time);
-	GetTimeFormatA(LOCALE_SYSTEM_DEFAULT, 0, &time, "hh':'mm':'ss tt", timeString, ARRAYSIZE(timeString));
+    GetTimeFormatA(LOCALE_SYSTEM_DEFAULT, 0, &time, "hh':'mm':'ss tt", timeString, ARRAYSIZE(timeString));
-	printf("The current UTC time is: %s\n", timeString);
+    fprintf(LOG_OUT, "The current UTC time is: %s\n", timeString);
 
     // Print a console header
-    fprintf(stderr, "Moonlight Internet Streaming Tester v" VER_VERSION_STR "\n\n");
+    fprintf(CONSOLE_OUT, "Moonlight Internet Streaming Tester v" VER_VERSION_STR "\n\n");
 
     int err = WSAStartup(MAKEWORD(2, 2), &wsaData);
     if (err != NO_ERROR) {
@@ -775,7 +816,7 @@ int main(int argc, char* argv[])
         return err;
     }
 
-    fprintf(stderr, "Checking if GameStream is enabled...\n");
+    fprintf(CONSOLE_OUT, "Checking if GameStream is enabled...\n");
 
     // First check if GameStream is enabled
     if (!IsGameStreamEnabled()) {
@@ -790,63 +831,138 @@ int main(int argc, char* argv[])
     char msgBuf[2048];
     char portMsgBuf[512];
 
-    fprintf(stderr, "Testing GameStream connectivity on this PC...\n");
+    fprintf(CONSOLE_OUT, "Testing GameStream connectivity on this PC...\n");
 
     // Try to connect via IPv4 loopback
     ss = {};
     sin.sin_family = AF_INET;
     sin.sin_addr = in4addr_loopback;
-    printf("Testing GameStream ports via loopback\n");
+    fprintf(LOG_OUT, "Testing GameStream ports via loopback\n");
-    if (!TestAllPorts(&ss, portMsgBuf, sizeof(portMsgBuf))) {
+    if (!TestAllPorts(&ss, portMsgBuf, sizeof(portMsgBuf), false, true)) {
         snprintf(msgBuf, sizeof(msgBuf),
             "Local GameStream connectivity check failed.\n\nFirst, try reinstalling GeForce Experience. If that doesn't resolve the problem, try temporarily disabling your antivirus and firewall.");
         DisplayMessage(msgBuf, "https://github.com/moonlight-stream/moonlight-docs/wiki/Troubleshooting");
         return -1;
     }
 
-    if (!FindLocalInterfaceIP4Address(&sin)) {
+    if (!FindLocalInterfaceIPAddress(AF_INET, &ss) && !FindLocalInterfaceIPAddress(AF_INET6, &ss)) {
         DisplayMessage("Unable to perform GameStream connectivity check. Please check your Internet connection and try again.");
         return -1;
     }
 
-    fprintf(stderr, "Testing GameStream connectivity on your local network...\n");
+    fprintf(CONSOLE_OUT, "Testing GameStream connectivity on your local network...\n");
 
-    // Try to connect via LAN IPv4 address
+    // Try to connect via LAN address
-    printf("Testing GameStream ports via local network\n");
+    fprintf(LOG_OUT, "Testing GameStream ports via local network\n");
-    if (!TestAllPorts(&ss, portMsgBuf, sizeof(portMsgBuf))) {
+    if (!TestAllPorts(&ss, portMsgBuf, sizeof(portMsgBuf), false, true)) {
         snprintf(msgBuf, sizeof(msgBuf),
             "Local network GameStream connectivity check failed. This is almost always caused by a firewall on your computer blocking the connection.\n\nTry temporarily disabling your antivirus and firewall.");
         DisplayMessage(msgBuf, "https://github.com/moonlight-stream/moonlight-docs/wiki/Troubleshooting");
         return -1;
     }
 
-    fprintf(stderr, "Detecting public IP address...\n");
 
-    bool rulesFound, igdDisconnected;
+    bool igdDisconnected;
     SOCKADDR_IN locallyReportedWanAddr;
-    if (!CheckWANAccess(&sin, &locallyReportedWanAddr, &rulesFound, &igdDisconnected)) {
+    char wanAddrStr[INET_ADDRSTRLEN];
-        return -1;
+
+    if (ss.ss_family == AF_INET) {
+        bool rulesFound;
+
+        fprintf(CONSOLE_OUT, "Detecting public IP address...\n");
+
+        if (!CheckWANAccess(&sin, &locallyReportedWanAddr, &rulesFound, &igdDisconnected)) {
+            return -1;
+        }
+
+        fprintf(CONSOLE_OUT, "Testing GameStream connectivity over the Internet...\n");
+
+        // Detect a double NAT by detecting STUN and and UPnP mismatches
+        if (sin.sin_addr.S_un.S_addr != locallyReportedWanAddr.sin_addr.S_un.S_addr) {
+            fprintf(LOG_OUT, "Testing GameStream ports via UPnP/NAT-PMP reported WAN address\n");
+
+            // We don't actually care about the outcome here but it's nice to have in logs
+            // to determine whether solving the double NAT will actually make Moonlight work.
+            TestAllPorts((PSOCKADDR_STORAGE)&locallyReportedWanAddr, portMsgBuf, sizeof(portMsgBuf), false, false);
+
+            fprintf(LOG_OUT, "Detected inconsistency between UPnP/NAT-PMP and STUN reported WAN addresses!\n");
+        }
+
+        inet_ntop(AF_INET, &sin.sin_addr, wanAddrStr, sizeof(wanAddrStr));
     }
-
+    else {
-    // Detect a double NAT by detecting STUN and and UPnP mismatches
+        // Go directly to the relay check if we have only IPv6 connectivity
-    if (sin.sin_addr.S_un.S_addr != locallyReportedWanAddr.sin_addr.S_un.S_addr) {
+        igdDisconnected = false;
-        printf("Testing GameStream ports via UPnP/NAT-PMP reported WAN address\n");
+        locallyReportedWanAddr = {};
-
+        goto RelayCheck;
-        // We don't actually care about the outcome here but it's nice to have in logs
-        // to determine whether solving the double NAT will actually make Moonlight work.
-        TestAllPorts((PSOCKADDR_STORAGE)&locallyReportedWanAddr, portMsgBuf, sizeof(portMsgBuf));
-
-        printf("Detected inconsistency between UPnP/NAT-PMP and STUN reported WAN addresses!\n");
     }
 
-    fprintf(stderr, "Testing GameStream connectivity over the Internet...\n");
-
-    char wanAddrStr[64];
-    inet_ntop(AF_INET, &sin.sin_addr, wanAddrStr, sizeof(wanAddrStr));
-
     // Try to connect via WAN IPv4 address
-    printf("Testing GameStream ports via STUN-reported WAN address\n");
+    fprintf(LOG_OUT, "Testing GameStream ports via STUN-reported WAN address\n");
-    if (!TestAllPorts(&ss, portMsgBuf, sizeof(portMsgBuf))) {
+    if (!TestAllPorts(&ss, portMsgBuf, sizeof(portMsgBuf), false, true)) {
+    RelayCheck:
+        struct addrinfo hint = {};
+        struct addrinfo* result;
+
+        // We can get here if the router doesn't support NAT reflection.
+        // We'll need to call out to our loopback server to get a second opinion.
+
+        hint.ai_family = AF_UNSPEC;
+        hint.ai_flags = AI_ADDRCONFIG;
+        err = getaddrinfo("loopback.moonlight-stream.org", NULL, &hint, &result);
+        if (err != 0 || result == NULL) {
+            fprintf(LOG_OUT, "getaddrinfo() failed: %d\n", err);
+        }
+        else {
+            bool allPortsFailedOnV4 = true;
+
+            // First try the relay server over IPv4. If this passes, it's considered a full success
+            fprintf(LOG_OUT, "Testing GameStream ports via IPv4 loopback server\n");
+            for (struct addrinfo* current = result; current != NULL; current = current->ai_next) {
+                if (current->ai_family == AF_INET) {
+                    fprintf(CONSOLE_OUT, "Testing GameStream connectivity over the Internet using a relay server...\n");
+                    if (TestAllPorts((PSOCKADDR_STORAGE)current->ai_addr, portMsgBuf, sizeof(portMsgBuf), true, true, &allPortsFailedOnV4)) {
+                        freeaddrinfo(result);
+                        goto AllTestsPassed;
+                    }
+                }
+            }
+
+            // If that fails, try the relay server over IPv6. If this passes, it will be a partial success
+            fprintf(LOG_OUT, "Testing GameStream ports via IPv6 loopback server\n");
+            for (struct addrinfo* current = result; current != NULL; current = current->ai_next) {
+                if (current->ai_family == AF_INET6) {
+                    fprintf(CONSOLE_OUT, "Testing GameStream connectivity over the Internet using an IPv6 relay server...\n");
+                    // Pass the portMsgBuf only if we've detected an IPv6-only setup. Otherwise, we want to preserve
+                    // the failing ports from the IPv4 to display in the error dialog.
+                    if (TestAllPorts((PSOCKADDR_STORAGE)current->ai_addr,
+                                     ss.ss_family == AF_INET6 ? portMsgBuf : NULL,
+                                     ss.ss_family == AF_INET6 ? sizeof(portMsgBuf) : 0, true, true)) {
+                        // We will terminate the test at the IPv6 limited connectivity warning in the following cases:
+                        // 1) Double-NAT/CGN - indicates the connection is fundamentally limited to IPv6 for end-to-end connectivity
+                        // 2) IPv6-only - indicates the connection is fundamentally limited to IPv6 for all connectivity
+                        // 3) All ports failed the test with our IPv4 relay - This is one final heuristic to weed out IPv4 misconfigurations. If we have some ports open,
+                        //                                                    it clearly indicates IPv4 support is possible, just currently misconfigured.
+                        //
+                        // Our last (implicit) heuristic is that we actually managed to establish an IPv6 connection. This means that there was either
+                        // no IPv6 firewall (hopefully not) or that we were able to talk to a PCP/IGDv6 gateway to allow us through. Hopefully if we have
+                        // a gateway that is unresponsive to UPnP/NAT-PMP, we wouldn't even be able to establish this connection so we would inherently fall
+                        // to the checks below for IPv4 issues.
+                        if (IsDoubleNAT(&locallyReportedWanAddr) || igdDisconnected || IsPossibleCGN(&locallyReportedWanAddr) || ss.ss_family == AF_INET6 || allPortsFailedOnV4) {
+                            snprintf(msgBuf, sizeof(msgBuf), "This PC has limited connectivity for Internet hosting. It will work only for clients on certain networks.\n\n"
+                                "If you want to try streaming with this configuration, you must pair Moonlight to your gaming PC from your home network before trying to stream over the Internet.\n\n"
+                                "To get full connectivity, please contact your ISP and ask for a \"public IP address\" which they may offer for free upon request. For more information and workarounds, click the Help button.");
+                            DisplayMessage(msgBuf, "https://github.com/moonlight-stream/moonlight-docs/wiki/Internet-Streaming-Errors#limited-connectivity-for-hosting-error", MpWarn);
+                            freeaddrinfo(result);
+                            return 0;
+                        }
+                    }
+                }
+            }
+
+            freeaddrinfo(result);
+        }
+
         // Many UPnP devices report IGD disconnected when double-NATed. If it was really offline,
         // we probably would not have even gotten past STUN.
         if (IsDoubleNAT(&locallyReportedWanAddr) || igdDisconnected) {
@@ -854,38 +970,24 @@ int main(int argc, char* argv[])
             DisplayMessage(msgBuf, "https://github.com/moonlight-stream/moonlight-docs/wiki/Internet-Streaming-Errors#connected-through-another-router-error");
         }
         else if (IsPossibleCGN(&locallyReportedWanAddr)) {
-            snprintf(msgBuf, sizeof(msgBuf), "Your ISP is running a Carrier-Grade NAT that is preventing you from hosting services like Moonlight on the Internet. Click the Help button for guidance on fixing this issue.");
+            snprintf(msgBuf, sizeof(msgBuf), "Your ISP is running a Carrier-Grade NAT that is preventing you from hosting services like Moonlight on the Internet.\n\n"
+                "Ask your ISP for a \"public IP address\" which they may offer for free upon request. For more information and workarounds, click the Help button.");
             DisplayMessage(msgBuf, "https://github.com/moonlight-stream/moonlight-docs/wiki/Internet-Streaming-Errors#carrier-grade-nat-error");
         }
-		else {
+        else {
-			struct hostent* host;
+            snprintf(msgBuf, sizeof(msgBuf), "Internet GameStream connectivity check failed.\n\n"
+                "Check that UPnP is enabled in your router settings. For more information and workarounds, click the Help button.\n\n"
+                "The following ports were not forwarded properly:\n%s", portMsgBuf);
+            DisplayMessage(msgBuf, "https://github.com/moonlight-stream/moonlight-docs/wiki/Internet-Streaming-Errors#internet-gamestream-connectivity-check-error");
+        }
 
-			// We can get here if the router doesn't support NAT reflection.
-			// We'll need to call out to our loopback server to get a second opinion.
-
-			printf("Testing GameStream ports via loopback server\n");
-
-			host = gethostbyname("loopback.moonlight-stream.org");
-			if (host != nullptr) {
-				sin.sin_addr = *(struct in_addr*)host->h_addr;
-				if (TestAllPorts((PSOCKADDR_STORAGE)&sin, portMsgBuf, sizeof(portMsgBuf))) {
-					goto AllTestsPassed;
-				}
-			}
-			else {
-				printf("gethostbyname() failed: %d\n", WSAGetLastError());
-			}
-		}
-
-        snprintf(msgBuf, sizeof(msgBuf), "Internet GameStream connectivity check failed. Click the Help button for guidance on fixing this issue.\n\nThe following ports were not forwarded properly:\n%s", portMsgBuf);
-        DisplayMessage(msgBuf, "https://github.com/moonlight-stream/moonlight-docs/wiki/Internet-Streaming-Errors#internet-gamestream-connectivity-check-error");
         return -1;
     }
 
 AllTestsPassed:
-    snprintf(msgBuf, sizeof(msgBuf), "This PC is ready to stream over the Internet!\n\n"
+    snprintf(msgBuf, sizeof(msgBuf), "This PC is ready to host over the Internet!\n\n"
-		"For the easiest setup, you should pair Moonlight to your PC from your home network before trying to stream over the Internet.\n\n"
+        "For the easiest setup, you should pair Moonlight to your gaming PC from your home network before trying to stream over the Internet.\n\n"
-		"If you can't, you can type the following address into Moonlight's Add PC dialog: %s", wanAddrStr);
+        "If you can't, you can type the following address into Moonlight's Add PC dialog: %s", wanAddrStr);
     DisplayMessage(msgBuf, nullptr, MpInfo);
 
     return 0;

mist/mist.h

@@ -0,0 +1,17 @@
+#pragma once
+
+#define _CRT_RAND_S
+#define _CRT_SECURE_NO_WARNINGS
+#include <stdlib.h>
+
+#define WIN32_LEAN_AND_MEAN
+#define _WINSOCK_DEPRECATED_NO_WARNINGS
+#include <Windows.h>
+#include <WinSock2.h>
+
+#include "..\version.h"
+
+#define CONSOLE_OUT stdout
+#define LOG_OUT stderr
+
+bool getExternalAddressPortIP4(int proto, unsigned short localPort, PSOCKADDR_IN wanAddr);

mist/mist.vcxproj

@@ -167,6 +167,7 @@
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="..\version.h" />
+    <ClInclude Include="mist.h" />
   </ItemGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">

mist/mist.vcxproj.filters

@@ -26,6 +26,9 @@
     <ClInclude Include="..\version.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="mist.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <ResourceCompile Include="mist.rc">

mist/stun.cpp

@@ -1,11 +1,4 @@
-#define _CRT_RAND_S
+#include "mist.h"
-#define _CRT_SECURE_NO_WARNINGS
-#include <stdlib.h>
-
-#define WIN32_LEAN_AND_MEAN
-#define _WINSOCK_DEPRECATED_NO_WARNINGS
-#include <Windows.h>
-#include <WinSock2.h>
 
 #include <stdio.h>
 
@@ -63,13 +56,13 @@ bool getExternalAddressPortIP4(int proto, unsigned short localPort, PSOCKADDR_IN
 
     host = gethostbyname("stun.moonlight-stream.org");
     if (host == nullptr) {
-        printf("gethostbyname() failed: %d\n", WSAGetLastError());
+        fprintf(LOG_OUT, "gethostbyname() failed: %d\n", WSAGetLastError());
         return false;
     }
 
     sock = socket(AF_INET, proto == IPPROTO_TCP ? SOCK_STREAM : SOCK_DGRAM, proto);
     if (sock == INVALID_SOCKET) {
-        printf("socket() failed: %d\n", WSAGetLastError());
+        fprintf(LOG_OUT, "socket() failed: %d\n", WSAGetLastError());
         return false;
     }
 
@@ -77,7 +70,7 @@ bool getExternalAddressPortIP4(int proto, unsigned short localPort, PSOCKADDR_IN
     bindAddr.sin_family = AF_INET;
     bindAddr.sin_port = htons(localPort);
     if (bind(sock, (struct sockaddr*)&bindAddr, sizeof(bindAddr)) == SOCKET_ERROR) {
-        printf("bind() failed: %d\n", WSAGetLastError());
+        fprintf(LOG_OUT, "bind() failed: %d\n", WSAGetLastError());
         closesocket(sock);
         return false;
     }
@@ -96,7 +89,7 @@ bool getExternalAddressPortIP4(int proto, unsigned short localPort, PSOCKADDR_IN
 
     // We'll connect() even for UDP so we can use send()/recv() and share more code
     if (connect(sock, (struct sockaddr*)&stunAddr, sizeof(stunAddr)) == SOCKET_ERROR) {
-        printf("connect() failed: %d\n", WSAGetLastError());
+        fprintf(LOG_OUT, "connect() failed: %d\n", WSAGetLastError());
         closesocket(sock);
         return false;
     }
@@ -116,7 +109,7 @@ bool getExternalAddressPortIP4(int proto, unsigned short localPort, PSOCKADDR_IN
     for (i = 0; i < tries; i++) {
         // Retransmit the request every second until the timeout elapses
         if (send(sock, (char *)&reqMsg, sizeof(reqMsg), 0) == SOCKET_ERROR) {
-            printf("send() failed: %d\n", WSAGetLastError());
+            fprintf(LOG_OUT, "send() failed: %d\n", WSAGetLastError());
             closesocket(sock);
             return false;
         }
@@ -135,7 +128,7 @@ bool getExternalAddressPortIP4(int proto, unsigned short localPort, PSOCKADDR_IN
             continue;
         }
         else if (selectRes == SOCKET_ERROR) {
-            printf("select() failed: %d\n", WSAGetLastError());
+            fprintf(LOG_OUT, "select() failed: %d\n", WSAGetLastError());
             closesocket(sock);
             return false;
         }
@@ -148,27 +141,27 @@ bool getExternalAddressPortIP4(int proto, unsigned short localPort, PSOCKADDR_IN
     closesocket(sock);
 
     if (bytesRead == 0) {
-        printf("No response from STUN server\n");
+        fprintf(LOG_OUT, "No response from STUN server\n");
         return false;
     }
     else if (bytesRead == SOCKET_ERROR) {
-        printf("Failed to read STUN binding response: %d\n", WSAGetLastError());
+        fprintf(LOG_OUT, "Failed to read STUN binding response: %d\n", WSAGetLastError());
         return false;
     }
     else if (bytesRead < sizeof(resp.hdr)) {
-        printf("STUN message truncated: %d\n", bytesRead);
+        fprintf(LOG_OUT, "STUN message truncated: %d\n", bytesRead);
         return false;
     }
     else if (htonl(resp.hdr.magicCookie) != STUN_MESSAGE_COOKIE) {
-        printf("Bad STUN cookie value: %x\n", htonl(resp.hdr.magicCookie));
+        fprintf(LOG_OUT, "Bad STUN cookie value: %x\n", htonl(resp.hdr.magicCookie));
         return false;
     }
     else if (memcmp(reqMsg.transactionId, resp.hdr.transactionId, sizeof(reqMsg.transactionId))) {
-        printf("STUN transaction ID mismatch\n");
+        fprintf(LOG_OUT, "STUN transaction ID mismatch\n");
         return false;
     }
     else if (htons(resp.hdr.messageType) != STUN_MESSAGE_BINDING_SUCCESS) {
-        printf("STUN message type mismatch: %x\n", htons(resp.hdr.messageType));
+        fprintf(LOG_OUT, "STUN message type mismatch: %x\n", htons(resp.hdr.messageType));
         return false;
     }
 
@@ -176,7 +169,7 @@ bool getExternalAddressPortIP4(int proto, unsigned short localPort, PSOCKADDR_IN
     bytesRead -= sizeof(resp.hdr);
     while (bytesRead > sizeof(*attribute)) {
         if (bytesRead < sizeof(*attribute) + htons(attribute->length)) {
-            printf("STUN attribute out of bounds: %d\n", htons(attribute->length));
+            fprintf(LOG_OUT, "STUN attribute out of bounds: %d\n", htons(attribute->length));
             return false;
         }
         // Mask off the comprehension bit
@@ -189,11 +182,11 @@ bool getExternalAddressPortIP4(int proto, unsigned short localPort, PSOCKADDR_IN
 
         ipv4Attrib = (PSTUN_MAPPED_IPV4_ADDRESS_ATTRIBUTE)attribute;
         if (htons(ipv4Attrib->hdr.length) != 8) {
-            printf("STUN address length mismatch: %d\n", htons(ipv4Attrib->hdr.length));
+            fprintf(LOG_OUT, "STUN address length mismatch: %d\n", htons(ipv4Attrib->hdr.length));
             return false;
         }
         else if (ipv4Attrib->addressFamily != 1) {
-            printf("STUN address family mismatch: %x\n", ipv4Attrib->addressFamily);
+            fprintf(LOG_OUT, "STUN address family mismatch: %x\n", ipv4Attrib->addressFamily);
             return false;
         }
 
@@ -207,6 +200,6 @@ bool getExternalAddressPortIP4(int proto, unsigned short localPort, PSOCKADDR_IN
         return true;
     }
 
-    printf("No XOR mapped address found in STUN response!\n");
+    fprintf(LOG_OUT, "No XOR mapped address found in STUN response!\n");
     return false;
 }

version.h

@@ -1,7 +1,7 @@
 #pragma once
 
-#define VER_VERSION                 4,0,0,0
+#define VER_VERSION                 4,1,0,0
-#define VER_VERSION_STR             "4.0.0.0"
+#define VER_VERSION_STR             "4.1.0.0"
 
 #define VER_COMPANYNAME_STR         "Moonlight Game Streaming Project"
-#define VER_PRODUCTNAME_STR         "Moonlight Internet Streaming Helper"
+#define VER_PRODUCTNAME_STR         "Moonlight Internet Hosting Tool"