ace nonblock

使用reactor, ACE_Sock_Stream进行收发数据。 nonblock模式下： [timeout参数均为NULL]

recv时， 可能返回-1. errno可能是EWOULDBLOCK（要求下次继续读）， 或者其他系统错。

无需使用recv_n/send_n

ACE_Sock_Stream::recv  ---->ACE::recv():
ssize_t ACE::recv (ACE_HANDLE handle,   void *buf, size_t len, int flags, const ACE_Time_Value *timeout)
{
  if (timeout == 0)
    <span style="color:#FF0000;">return ACE_OS::recv (handle, (char *) buf, len, flags);</span>
  else
    {
      int val = 0;
      if (ACE::enter_recv_timedwait (handle, timeout, val) ==-1)
        return -1;
      else
        {
          ssize_t bytes_transferred =
            ACE_OS::recv (handle, (char *) buf, len, flags);
          ACE::restore_non_blocking_mode (handle, val);
          return bytes_transferred;
        }
    }
}

ACE::recv--->ACE_OS::recv():
ACE_INLINE ssize_t  ACE_OS::recv (ACE_HANDLE handle, char *buf, size_t len, int flags)
{
  ACE_OS_TRACE ("ACE_OS::recv");

  // On UNIX, a non-blocking socket with no data to receive, this
  // system call will return EWOULDBLOCK or EAGAIN, depending on the
  // platform.  UNIX 98 allows either errno, and they may be the same
  // numeric value.  So to make life easier for upper ACE layers as
  // well as application programmers, always change EAGAIN to
  // EWOULDBLOCK.  Rather than hack the ACE_OSCALL_RETURN macro, it's
  // handled explicitly here.  If the ACE_OSCALL macro ever changes,
  // this function needs to be reviewed.  On Win32, the regular macros
  // can be used, as this is not an issue.
#if defined (ACE_LACKS_RECV)
  ACE_UNUSED_ARG (handle);
  ACE_UNUSED_ARG (buf);
  ACE_UNUSED_ARG (len);
  ACE_UNUSED_ARG (flags);
  ACE_NOTSUP_RETURN (-1);
#elif defined (ACE_WIN32)
  ACE_SOCKCALL_RETURN (::recv ((ACE_SOCKET) handle, buf,
                               static_cast<int> (len), flags), ssize_t, -1);
#else
  <span style="color:#FF0000;">ssize_t ace_result_;
  ace_result_ = ::recv ((ACE_SOCKET) handle, buf, len, flags);

# if !(defined (EAGAIN) && defined (EWOULDBLOCK) && EAGAIN == EWOULDBLOCK)
  // Optimize this code out if we can detect that EAGAIN ==
  // EWOULDBLOCK at compile time.  If we cannot detect equality at
  // compile-time (e.g. if EAGAIN or EWOULDBLOCK are not preprocessor
  // macros) perform the check at run-time.  The goal is to avoid two
  // TSS accesses in the _REENTRANT case when EAGAIN == EWOULDBLOCK.
  if (ace_result_ == -1
#  if !defined (EAGAIN) || !defined (EWOULDBLOCK)
      && EAGAIN != EWOULDBLOCK
#  endif  /* !EAGAIN || !EWOULDBLOCK */
      && errno == EAGAIN)
    {
      errno = EWOULDBLOCK;
    }
# endif /* EAGAIN != EWOULDBLOCK*/

  return ace_result_;</span>
#endif /* ACE_LACKS_RECV */
}

同样， ACE_Sock_Stream::send--->ACE_OS::write---->::write