C++判断主机是否处于联网状态

 #include #include  #pragma comment(lib,"ws2_32.lib") #define LEN 1024 //接收数据的大小 using namespace std; int main() { //加载套接字库 WORD wVersionRequested; WSADATA wsaData; int err; wVersionRequested = MAKEWORD( 1, 1 );  //初始化Socket动态连接库,请求1.1版本的winsocket库 err = WSAStartup( wVersionRequested, &wsaData ); if ( err != 0 ) { return 0; } if ( LOBYTE( wsaData.wVersion ) != 1 ||  //判断请求的winsocket是不是1.1的版本 HIBYTE( wsaData.wVersion ) != 1 ) { WSACleanup( );  //清盘 return 0;   //终止对winsocket使用 } //WSADATA ws; //WSAStartup(MAKEWORD(2,2),&ws);// char http[60] = "www.google.com";  //访问谷歌网页 SOCKET sock = socket(AF_INET,SOCK_STREAM,0);//建立socket if (sock == INVALID_SOCKET) { cout<<"建立访问socket套接字失败!"<h_addr,sizeof(hostadd));//将返回的IP信息Copy到地址结构 hostadd.sin_family = AF_INET; hostadd.sin_port = htons(80); char buf[LEN]="GET / HTTP/1.1\r\nHost: ";//构造Http请求数据包 strcat(buf,inet_ntoa(hostadd.sin_addr)); strcat(buf," \r\nContent-Length: 10\r\n\r\n"); strcat(buf,"Connection:close"); int time = 1000; //超时时间 setsockopt(sock,SOL_SOCKET,SO_RCVTIMEO,(char*)&time,sizeof(time)); if (connect(sock,(sockaddr*)&hostadd,sizeof(hostadd)) == SOCKET_ERROR)//连接请求 { cout<<"与网页建立连接失败!"<