C++判断主机是否处于联网状态

#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;
}