c++ - select 不等待 C++ 套接字中的超时值

Question

我编写了一个服务器代码，它接受新客户端和来自客户端的数据。但问题是，尽管没有来自客户端的数据，但 select 并没有等到超时。我想等待 5 秒并向可用的客户端发送心跳。但它在第一次迭代中等待 5 秒，然后在下一次迭代中快速发送心跳。如何解决这个问题呢。提前致谢。

void * Communicate(void * id)
{
int *iSockID = (int *) id;
int listener =  *iSockID;

fd_set master;    // master file descriptor list
fd_set read_fds;  // temp file descriptor list for select() read
fd_set write_fds; // temp file descriptor list for select() read
int fdmax;        // maximum file descriptor number

int i, j, rv;

FD_ZERO(&master);    // clear the master and temp sets
FD_ZERO(&read_fds);
FD_ZERO(&write_fds);
// add the listener to the master set
FD_SET(listener, &master);
printf("Listener is %d \n" , listener);

// keep track of the biggest file descriptor
fdmax = listener; // so far, it's this one
//accept 3 clients


// main loop
for(;;) {
    read_fds = master; // copy it
    write_fds = master;
    struct timeval tv;
    tv.tv_sec = 5;
    tv.tv_usec = 0;
    int iResult = select(fdmax+1, &read_fds, &write_fds, NULL, &tv) ;
    if (iResult == -1) 
    {
        perror("select");
        exit(4);
    }

    for(i = 0; i <= fdmax; i++) 
    {           
        //send work for clients
        SendHeartBeats(write_fds , fdmax , listener , i );

    }

    // run through the existing connections looking for data to read
    // ADD NEW CONNECTIONS READ FROM CONNECTIONS    
    for(i = 0; i <= fdmax; i++)
    {   


        if (FD_ISSET(i, &read_fds)) 
        { // we got one!!
            // handle new connections               
            if (i == listener) 
            {                                    
                AcceptNewClients(master , fdmax , listener );   
            } else 
            {
                AccepeDataFromClients(i , master);
            } // END handle data from client
        } // END got new incoming connection
    } // END looping through file descriptors
    sleep(3);
} // END for(;;)
return 0;
}

Answer 1

您不能通过 equals 来 fd_set 变量。您需要使用FD_COPY。如果不这样做，您只需复制实际数据的句柄，该数据已标记为已完成。