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From: tmoran@acm.org
Newsgroups: comp.lang.ada
Subject: Re: [OT] Two sockets questions
References: <5d6fdb61.0305100606.1a36d426@posting.google.com>
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Date: 2003-05-10T18:01:59+00:00
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>in the Gnat list the article where Microsoft explains that Windows
>will return EWOULDBLOCK in an asynchronous connect. The connect is in
>effect being performed and Gnat is simply reporting the underlying
>Windows error.
  The Open code in the Claw-less sockets that will soon(?) appear on
www.adapower.com contains:

    if Connect(Socket.Handle, Sockaddr'unchecked_access) = Socket_Error then
      Error := WSAGetLastError;
      if Error = WSAE_Wouldblock then
        loop
          FD.Count := 1;
          FD.Set(FD.Set'first) := Socket.Handle;
          Result
            := Select_function(0,
                               Read_FD_Set       => Null_FD_Set'unchecked_access,
                               Write_FD_Set      => FD'unchecked_access,
                               Exceptions_FD_Set => Null_FD_Set'unchecked_access,
                               Timeout           => Zerowait'unchecked_access);
          exit when Result = 1;
          if Result = Socket_Error then
          ...
It's intended for blocking sockets, so it sits around and polls till the
select says its writable, or some other error is returned.  It actually
opens as non-blocking so it can get control back from the OS to do this
polling, and timeout checking, etc.