sockets - 在非阻塞套接字上检查WSACONREFUSED

Question

我终于设法按照前面thread中提供的建议编写了一个用于主机发现的非阻塞套接字代码。我发现代码的逻辑是在80,139等端口上与主机建立套接字连接。如果成功，则主机存在；如果主机通过发送RST数据包终止 session ，则该主机存在。通过使用阻塞套接字，我能够检查来自主机的WSACONREFUSED数据包的RST，但是即使从主机发送了RST数据包以终止 session ，非阻塞套接字也始终返回0。有没有办法在非阻塞模式下检查RST数据包？ 。相同的代码如下

 #ifndef UNICODE
 #define UNICODE
 #endif

 #define WIN32_LEAN_AND_MEAN

 #include <winsock2.h>
 #include <ws2tcpip.h>
 #include <stdio.h>

 // Need to link with Ws2_32.lib
 #pragma comment(lib, "ws2_32.lib")

 int port[]={80,139}; //port number for scanning 

 int wmain()
 {

    // Initialize Winsock
    WSADATA wsaData;
    int i=0,flag=0;
    char ip[20];
    int iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
    if (iResult != NO_ERROR) {
    wprintf(L"WSAStartup function failed with error: %d\n", iResult);
    return 1;
    }

    SOCKET socketarray[2];

    sockaddr_in clientService;

    // Create a SOCKET for connecting to server

    for(i=0;i<2;i++){
    socketarray[i]=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);
    }

    printf("\n Enter the Ip Address : ");
    scanf("%s",ip);

    clientService.sin_family = AF_INET;
    clientService.sin_addr.S_un.S_addr = inet_addr(ip);

    u_long iMode=1;

 for(i=0;i<2;i++)
 {
    ioctlsocket(socketarray[i],FIONBIO,&iMode);
 }

     fd_set WriteFDs;
     FD_ZERO(&WriteFDs);
     timeval timer;
     timer.tv_sec=5;
     timer.tv_usec=5000000;

 for(i=0;i<2;i++)
 {        
              FD_SET(socketarray[i],&WriteFDs);
              clientService.sin_port = htons((unsigned short)port[i]);
              connect(socketarray[i], (SOCKADDR *) & clientService, sizeof(clientService));
              iResult=select(0, NULL, &WriteFDs,NULL,&timer);

      if(iResult==SOCKET_ERROR||iResult==0)
      {
         printf("The return value of the function = %d",iResult);
            wprintf(L"\n Select failed for the port number %d with error %d ",port[i], WSAGetLastError());

      }
      else
      {
          printf("\n The return value of the function = %d",iResult);
          wprintf(L"\n Select was success  for the port number %d ",port[i]);
      }
}

 for(i=0;i<2;i++)
 {
    closesocket(socketarray[i]);
 }


 WSACleanup();
 return 0;
}

Answer 1

完成非阻塞连接后，必须在套接字上选择()直到可写。然后通过setsockopt()获取最后一个套接字错误。如果没有，则表明您已连接;如果存在，请查看其状态。