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Question

中使用輪詢函數的下列代碼存在困惑，下面的代碼是TCP服務器。

bool Run() 
{ 
    bool result = false; 
    m_Socket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP); 

    if (INVALIDE_SOCKET == m_Socket) 
    { 
     printf("Invalide socket..."); 
     return result; 
    } 

    sockaddr_in servAddr; 
    unsigned int sockAddrSize = sizeof(sockaddr_in); 
    bzero(&servAddr, sockAddrSize); 
    servAddr.sin_family = AF_INET; 
    servAddr.sin_addr.s_addr = htonl(INADDR_ANY); 
    servAddr.sin_port = htons(m_Port); 

    if (0 != bind(m_Socket, (sockaddr *)&servAddr, sockAddrSize)) 
    { 
     printf("Can not bind socket addres to socket file...\n"); 
     return result; 
    } 

    if (0 != listen(m_Socket, MAX_CONNECTION)) 
    { 
     printf("Can not listen socket...\n"); 
     return result; 
    } 


    printf("Server is stared. Please enter any key to continue...\n"); 
    getchar(); 
    system("clear"); 

    m_Listener.Start(); 
    m_DataReader.Start(); 

    sockaddr_in temp; 
    while (true) 
    { 
     bzero(&temp, sockAddrSize); 
     int tempSocket = accept(m_Socket, (sockaddr *)&temp, &sockAddrSize); 

     if (-1 == tempSocket) 
     { 
      printf("accept is fialed...\n"); 
     } 
     else 
     { 
      printf("A connection is established!\n"); 
     } 

     //This is my intention:blocking after the client is connected and before the client to be send any data. 
     //When the client sends data, the program will print '---------------'. 
     pollfd tempTest; 
     tempTest.events = POLLRDNORM; 
     tempTest.revents = 0; 
     tempTest.fd = tempSocket; 

     int pollRes = poll(&tempTest, 1, -1); 
     if (pollRes == 1 && POLLRDNORM == tempTest.revents) 
     { 
      printf("-------------------\n"); 
     } 

    } 
    return result; 
} 

事實上，當將客戶端連接到服務器，並且不發送任何數據，下列代碼不符合我的意圖，因爲它沒有被阻塞並且印刷「--------- -----'也：

//This is my intention:blocking after the client is connected and before the client to be send any data. 
    //When the client sends data, the program will print '---------------'. 
    pollfd tempTest; 
    tempTest.events = POLLRDNORM; 
    tempTest.revents = 0; 
    tempTest.fd = tempSocket; 

    int pollRes = poll(&tempTest, 1, -1); 
    if (pollRes == 1 && POLLRDNORM == tempTest.revents) 
    { 
     printf("-------------------\n"); 
    } 

Answer 1

你看過poll(2)手冊頁嗎？

您應該測試的poll這樣的結果代碼：

fflush(NULL); 
int res = poll(&test, 1, -1); 
if (res < 0) { 
    perror("poll"); 
    exit(EXIT_FAILURE); /// or some other error handling 
}; 
printf("poll gave %d\n", res); 

BTW，我會打電話fflush(3)投票之前，我將打印的poll結果至少進行調試。

您當然想在成功poll後處理follfd.revents;如果是POLLNVAL或POLLERR，您應該特別小心。

你也應該測試socket(2)同樣（你應該bind(2)或connect(2)之前poll ING，見socket(7)也許tcp(7)或unix(7)，我想這就是爲什麼poll失敗或者說POLLNVAL或POLLERR！）

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