What is the fastest way to check an internet connection using C or C++? -

i'm trying write program in c/c++ check internet connection on windows machine. appreciated. thank you.

i can show short way, based on microsoft example. in fact, way make sure can connect internet try connect server in internet. applications use google target-server or own server (if have one). modified example connect google on port 80. if program return 0, success, otherwise returns 1. should give startpoint own solution:

// example from: // https://msdn.microsoft.com/en-us/library/windows/desktop/ms737591(v=vs.85).aspx #define win32_lean_and_mean  #include <windows.h> #include <winsock2.h> #include <ws2tcpip.h> #include <stdlib.h> #include <stdio.h>   // need link ws2_32.lib, mswsock.lib, , advapi32.lib #pragma comment (lib, "ws2_32.lib") #pragma comment (lib, "mswsock.lib") #pragma comment (lib, "advapi32.lib")   #define default_buflen 512 #define default_port "80"  int __cdecl main(int argc, char **) {     wsadata wsadata;     socket connectsocket = invalid_socket;     struct addrinfo *result = null,         *ptr = null,         hints;     char *sendbuf = "this test";     char recvbuf[default_buflen];     int iresult;     int recvbuflen = default_buflen;       // initialize winsock     iresult = wsastartup(makeword(2, 2), &wsadata);     if (iresult != 0) {         printf("wsastartup failed error: %d\n", iresult);         return 1;     }      zeromemory(&hints, sizeof(hints));     hints.ai_family = af_unspec;     hints.ai_socktype = sock_stream;     hints.ai_protocol = ipproto_tcp;      // resolve server address , port     iresult = getaddrinfo("www.google.com", default_port, &hints, &result);     if (iresult != 0) {         printf("getaddrinfo failed error: %d\n", iresult);         wsacleanup();         return 1;     }      // attempt connect address until 1 succeeds     (ptr = result; ptr != null; ptr = ptr->ai_next) {          // create socket connecting server         connectsocket = socket(ptr->ai_family, ptr->ai_socktype,             ptr->ai_protocol);         if (connectsocket == invalid_socket) {             printf("socket failed error: %ld\n", wsagetlasterror());             wsacleanup();             return 1;         }          // connect server.         iresult = connect(connectsocket, ptr->ai_addr, (int)ptr->ai_addrlen);         if (iresult == socket_error) {             closesocket(connectsocket);             connectsocket = invalid_socket;             continue;         }         break;     }      freeaddrinfo(result);      if (connectsocket == invalid_socket) {         printf("unable connect server!\n");         wsacleanup();         return 1;     }      // send initial buffer     iresult = send( connectsocket, sendbuf, (int)strlen(sendbuf), 0 );     if (iresult == socket_error) {         printf("send failed error: %d\n", wsagetlasterror());         closesocket(connectsocket);         wsacleanup();         return 1;     }      printf("bytes sent: %ld\n", iresult);      // shutdown connection since no more data sent     iresult = shutdown(connectsocket, sd_send);     if (iresult == socket_error) {         printf("shutdown failed error: %d\n", wsagetlasterror());         closesocket(connectsocket);         wsacleanup();         return 1;     }      // receive until peer closes connection /*  {          iresult = recv(connectsocket, recvbuf, recvbuflen, 0);         if ( iresult > 0 )             printf("bytes received: %d\n", iresult);         else if ( iresult == 0 )             printf("connection closed\n");         else             printf("recv failed error: %d\n", wsagetlasterror());      } while( iresult > 0 ); */     // cleanup     closesocket(connectsocket);     wsacleanup();      return 0; } 

if change buffer "this test" valid http request, can response can read (i comment part away). not necessary connect tcp/ip says connection possible. there of course udp ping ways, have (in opinion) no advantage. name resolving can dropped , can use ip directly. name resolving no sign of working internet provider have internal dns server can if connection internet not possible.