recv（）失败：错误的文件描述符c ++ Linux

Question

I have a problem. My program includes 10 TCP Server at the sam etime. As soon as a request from a client is noticed, the appropriate tcp server socket will accept the connection and handle it in a seperate thread. I know this is not the most efficient way of solving my actual problem but okay..

In main I have a for loop that will call a function in an object called Peer which is StartThread()

for (it= ListOfPeers.begin();it!= ListOfPeers.end();it++)
{
    (*it).second->StartThread();
}

Of cause there are some conditions that this loop will be used but i wanted to narrow the code as much down as possible.

The function StartThread will be called in each peer object:

    void StartThread()
{
    pthread_t threadDoEvent;
    pthread_create( &threadDoEvent, NULL, &DoEvent_helper,this);
    pthread_detach(threadDoEvent);
}

void *DoEvent_helper( void *ptr ) // Helper to implement thread
{
    return ((Peer *)ptr)->DoEvent();
}

DoEvent is the function which will handle the request and connection:

void* DoEvent()
{
    unsigned char  buffer[1024];
    int rc;
    int    close_conn= FALSE;
    int new_sd;

    new_sd = accept(Socket, NULL, NULL);
    if (new_sd < 0)
    {
        if (errno != EWOULDBLOCK)
        {
            perror("  accept() failed");
            close_conn = TRUE;
        }
    }


    do
    {
        rc = recv(new_sd, buffer, sizeof(buffer), 0);
        if (rc < 0)
        {
            if (errno != EWOULDBLOCK)
            {
                perror("  recv() failed");
                close_conn = TRUE;
            }
            break;
        }

        if (rc == 0)
        {
            printf("  Connection closed\n");
            close_conn = TRUE;
            break;
        }

[DO SOMETHING WITH THE BUFFER]

        rc = send(new_sd, buffer, len, 0);
        if (rc <= 0)
        {
            perror("  send() failed");
            close_conn = TRUE;
            break;
        }
    }while (close_conn==FALSE);
     close(new_sd);
}

My Question is why am I receiving an error : recv() failed: Bad file descriptor???? When I am adding a sleep(1) in between pthread_create and pthread_detach, everything is working! Can somebody explain this circumstances to me? or maybe help me solving my problem?

Thanks!

Answer 1

Well you do try to receive even if accept fails. This leads me to believe that you haven't properly set up the passive Socket file descriptor properly before trying to accept from it.

If you set up the Socket descriptor in the main thread, then it could be that the new thread starts and runs before you do that.

Answer 2

Make sure new_sd is in persistent memory. eg if it is allocated by a function that launches the thread and exits, then new_sd will be pointing to junk. (at least that was the case for me)