直接让本机访问一个网站，如果成功的话，就说明成功联网，没有访问成功，则说明没有联网！！！
- #include<iostream>
- #include <WINSOCK2.H>
- #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!"<<endl;
- return 0;
- }
- sockaddr_in hostadd;
- hostent* host = gethostbyname(http);//取得主机的IP地址
- if(host==NULL)
- {
- cout<<"主机处于没有联网状态;"<<endl;
- return 0;
- }
- cout<<"主机处于联网状态，现在可以进行通信!"<<endl;
- memcpy(&hostadd,host->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!"<<endl;
- return 0;
- }
- if (SOCKET_ERROR == send(sock,buf,strlen(buf)+1,0))//发送构造好的Http请求包
- {
- cout<<"发送数据包失败!"<<endl;
- return 0;
- }
- memset(buf,0,LEN);
- recv(sock,buf,LEN,0); //接收返回的数据
- cout<<"从网页中获取的数据为:"<<buf;
- closesocket(sock);
- WSACleanup();
- return 0;
- }