sockets - 从套接字部分读取数据，但只读取一次

Question

我想从 uClinux 上的串口获取数据。工作原理：我有想要进入引导加载程序模式的外围设备。为此，我必须发送数据 i2500$，这意味着它处于引导加载程序模式。不幸的是，我只能读取 >i2，如果我使用我的方法，它不再返回数据，或者如果我重置设备并重复开始跳转到引导加载程序

int TEnforaUpdate::ReadFromComport (unsigned long timeouta, unsigned long size)
{
  FD_SET(fdCom, &read_fds);
  int retValue = 0;
  // Set timeout to x microseconds
  struct timeval timeout;
  timeout.tv_sec = 0;
  timeout.tv_usec = 1000 * timeouta;
  // Wait for input to become ready or until the time out; the first parameter is
  // 1 more than the largest file descriptor in any of the sets
  if ((select (fdCom + 1, &read_fds, &write_fds, &except_fds, &timeout) == 1)
      && (FD_ISSET(fdCom,&read_fds)))
  {
    //read max
    retValue = read (fdCom, RxBuffer, RX_BUFFER_SIZE);
    printf ("Read %d bytes: ", retValue);
    int i;
    for (i = 0; i < retValue; i++)
      printf ("[%02x]", RxBuffer[i]);
    printf ("\n");   
  }
  else
    return 1;
  if (retValue > 2)
  {
    strcpy (answer, (char*) RxBuffer);
    //remove trashes from buffer
    memset (RxBuffer, 0x00, RX_BUFFER_SIZE);
    printf ("Comport answers: %s \n", answer);
  }
  FD_CLR(fdCom, &read_fds);
  tcflush (fdCom, TCIFLUSH);
  return retValue;
}