How do I find out a public IP address on the Internet using the Win32 API?

Question

How do I find out a public IP address on the Internet using the Win32 API?

I am interested in the public ip address, not the IP address of the local network. Interested in IPv4 and IPv6.

Now I find out my ip address like this: I go to some site that determines the ip address, and the site tells me my ip address. I need to do this using the Win32 API.

I am interested in the Win32 API, and not any programming languages (C++, C#, etc.).

Answer 1

Yes, you need to use an external website.

For example with Wininet on my PC :

					HINTERNET hInternet = InternetOpen(NULL, INTERNET_OPEN_TYPE_PRECONFIG_WITH_NO_AUTOPROXY, NULL, NULL, 0);
					if (hInternet != NULL)
					{
						HINTERNET hFile = InternetOpenUrl(hInternet, _T("https://api.ipify.org"), NULL, 0, INTERNET_FLAG_RELOAD, 0);
						if (hFile != NULL)
						{
							CHAR sBuffer[MAX_PATH];
							TCHAR wsBuffer[MAX_PATH];
							DWORD nRead;
							BOOL bRet = InternetReadFile(hFile, sBuffer, sizeof(sBuffer), &nRead);
							if (bRet)
							{
								sBuffer[nRead] = '\0';
								MultiByteToWideChar(CP_ACP, 0, sBuffer, -1, wsBuffer, MAX_PATH);
								TCHAR wsMessage[MAX_PATH] = _T("");
								wsprintf(wsMessage, _T("External IP : %s"), wsBuffer);
								MessageBox(NULL, wsMessage, _T("Information"), MB_OK | MB_ICONINFORMATION);
							}
							InternetCloseHandle(hFile);							
						}
						InternetCloseHandle(hInternet);
					}

Answer 2

You just need to do a Http get operation. Here's an example:

static LPCWSTR AcceptTypes[]{ L"text/*", NULL };

static std::string GetIPAddressFromService()
{
	std::string sMyPublicAddress;
	unique_HINTERNET hOpen{ InternetOpen( L"", INTERNET_OPEN_TYPE_PRECONFIG, NULL, NULL, 0 ) };
	if ( hOpen != NULL )
	{
		unique_HINTERNET hConn{ InternetConnect( hOpen.get(), L"api.ipify.org", INTERNET_DEFAULT_HTTPS_PORT, NULL, NULL, INTERNET_SERVICE_HTTP, 0, 1 ) };
		if ( hConn != NULL )
		{
			// Try 3x before giving up so as not to wait excessively
			for ( int rcnt = 0; (rcnt < 3) && sMyPublicAddress.empty(); ++rcnt )
			{
				// GET is the default; use https
				unique_HINTERNET hReq{ HttpOpenRequest( hConn.get(), NULL, L"", NULL, NULL, AcceptTypes, INTERNET_FLAG_NO_UI | INTERNET_FLAG_SECURE, 1 ) };
				if ( hReq != NULL )
				{
					if ( HttpSendRequest( hReq.get(), NULL, 0, NULL, 0 ) )
					{
						// The expected response is the IP (v4) address as a string
						char ipAddrStr[sizeof( "255.255.255.255" )];
						DWORD BytesRead;
						if ( InternetReadFile( hReq.get(), ipAddrStr, sizeof( ipAddrStr ), &BytesRead ) )
						{
							sMyPublicAddress = std::string( ipAddrStr, BytesRead );
							// Check what we have is an ipv4 address by converting it
							IN_ADDR inaddr;
							int rv = inet_pton( AF_INET, sMyPublicAddress.c_str(), &inaddr );
							// 1 means OK!
							if ( rv != 1 )
							{
								// We got an invalid string for the address, clear it and retry
								sMyPublicAddress.clear();
							}
						}
					}
				}
			}
		}
	}
	return sMyPublicAddress;
}

Answer 3

Hello @Participant, A way is GetAdaptersAddresses(). Also see the question as a result of quick search.

Answer 4

XiaoYang - MSFT, the link you provided discusses the topic: How to get the local IP address of Windows system? Pay attention to "local". I use the term "public" in my first post. Be careful when you give advice.

Since you do not see the difference between "local" and "public", I assume that the "GetAdaptersAddresses" function you proposed will not give the desired result.

Answer 5

RLWA32, I'm accessing the Internet through a router.

David Lowndes, are you suggesting using the Win32 API or a website that will tell me my ip address?