使用C或C++检查互联网连接的最快方法是什么

我只能根据微软的一个例子向您展示一个简短的方法。事实上，确保你可以连接到互联网的唯一方法是尝试连接到互联网上的服务器。大多数应用程序使用谷歌作为目标服务器或自己的服务器(如果有)。我修改了这个例子，在端口80上连接到谷歌。如果程序返回0，则表示成功，否则返回1。这应该给你一个自己的解决方案的起点：

// 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 to link with Ws2_32.lib, Mswsock.lib, and 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 is a 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 with error: %dn", iResult);
return 1;
}
ZeroMemory(&hints, sizeof(hints));
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;
// Resolve the server address and port
iResult = getaddrinfo("www.google.com", DEFAULT_PORT, &hints, &result);
if (iResult != 0) {
printf("getaddrinfo failed with error: %dn", iResult);
WSACleanup();
return 1;
}
// Attempt to connect to an address until one succeeds
for (ptr = result; ptr != NULL; ptr = ptr->ai_next) {
// Create a SOCKET for connecting to server
ConnectSocket = socket(ptr->ai_family, ptr->ai_socktype,
ptr->ai_protocol);
if (ConnectSocket == INVALID_SOCKET) {
printf("socket failed with error: %ldn", WSAGetLastError());
WSACleanup();
return 1;
}
// Connect to 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 to connect to server!n");
WSACleanup();
return 1;
}
// Send an initial buffer
iResult = send( ConnectSocket, sendbuf, (int)strlen(sendbuf), 0 );
if (iResult == SOCKET_ERROR) {
printf("send failed with error: %dn", WSAGetLastError());
closesocket(ConnectSocket);
WSACleanup();
return 1;
}
printf("Bytes Sent: %ldn", iResult);
// shutdown the connection since no more data will be sent
iResult = shutdown(ConnectSocket, SD_SEND);
if (iResult == SOCKET_ERROR) {
printf("shutdown failed with error: %dn", WSAGetLastError());
closesocket(ConnectSocket);
WSACleanup();
return 1;
}
// Receive until the peer closes the connection
/*  do {
iResult = recv(ConnectSocket, recvbuf, recvbuflen, 0);
if ( iResult > 0 )
printf("Bytes received: %dn", iResult);
else if ( iResult == 0 )
printf("Connection closedn");
else
printf("recv failed with error: %dn", WSAGetLastError());
} while( iResult > 0 );
*/
// cleanup
closesocket(ConnectSocket);
WSACleanup();
return 0;
}

如果您将缓冲区从"这是一个测试"更改为一个有效的http请求，您甚至可以得到一个可以阅读的响应(我对此部分进行了注释)。这是不必要的，因为与TCP/IP的连接已经表明连接是可能的。当然有UDP ping方式，但(在我看来)它们没有优势。可以删除名称解析，并且可以直接使用ip。名称解析并不是互联网正常工作的迹象，因为大多数提供商都有内部DNS服务器，即使无法连接到互联网，该服务器也可以启动。

我见过人们使用InternetCheckConnection函数，这里有文档。