[转贴] C++ 判断主机是否处于联网状态下

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！！！

[cpp]view plaincopyprint?

1. #include<iostream>
2. #include <WINSOCK2.H>
3. #pragma comment(lib,"ws2_32.lib")
4. #define LEN 1024 //接收数据的大小
5. using namespace std;
6. int main()
7. {
8. //加载套接字库
9. WORD wVersionRequested;
10. WSADATA wsaData;
11. int err;
12. wVersionRequested = MAKEWORD( 1, 1 ); //初始化Socket动态连接库,请求1.1版本的winsocket库
13. err = WSAStartup( wVersionRequested, &wsaData );
14. if ( err != 0 ) {
15. return 0;
16. }
17. if ( LOBYTE( wsaData.wVersion ) != 1 || //判断请求的winsocket是不是1.1的版本
18. HIBYTE( wsaData.wVersion ) != 1 ) {
19. WSACleanup( ); //清盘
20. return 0; //终止对winsocket使用
21. }
22. //WSADATA ws;
23. //WSAStartup(MAKEWORD(2,2),&ws);//
24. char http[60] = "www.google.com"; //访问谷歌网页
25. SOCKET sock = socket(AF_INET,SOCK_STREAM,0);//建立socket
26. if (sock == INVALID_SOCKET)
27. {
28. cout<<"建立访问socket套接字失败!"<<endl;
29. return 0;
30. }
31. sockaddr_in hostadd;
32. hostent* host = gethostbyname(http);//取得主机的IP地址
33. if(host==NULL)
34. {
35. cout<<"主机处于没有联网状态;"<<endl;
36. return 0;
37. }
38. cout<<"主机处于联网状态，现在可以进行通信!"<<endl;
39. memcpy(&hostadd,host->h_addr,sizeof(hostadd));//将返回的IP信息Copy到地址结构
40. hostadd.sin_family = AF_INET;
41. hostadd.sin_port = htons(80);
42. char buf[LEN]="GET / HTTP/1.1\r\nHost: ";//构造Http请求数据包
43. strcat(buf,inet_ntoa(hostadd.sin_addr));
44. strcat(buf," \r\nContent-Length: 10\r\n\r\n");
45. strcat(buf,"Connection:close");
46. int time = 1000; //超时时间
47. setsockopt(sock,SOL_SOCKET,SO_RCVTIMEO,(char*)&time,sizeof(time));
48. if (connect(sock,(sockaddr*)&hostadd,sizeof(hostadd)) == SOCKET_ERROR)//连接请求
49. {
50. cout<<"与网页建立连接失败!"<<endl;
51. return 0;
52. }
53. if (SOCKET_ERROR == send(sock,buf,strlen(buf)+1,0))//发送构造好的Http请求包
54. {
55. cout<<"发送数据包失败!"<<endl;
56. return 0;
57. }
58. memset(buf,0,LEN);
59. recv(sock,buf,LEN,0); //接收返回的数据
60. cout<<"从网页中获取的数据为:"<<buf;
61. closesocket(sock);
62. WSACleanup();
63. return 0;
64. }