Re: [Caml-list] Unix.connect for non-blocking sockets on Windows

[Jerome Vouillon <Jerome.Vouillon@pps.jussieu.fr>]

Hi Jérémie,

On Fri, Sep 14, 2012 at 04:27:17PM +0200, Jérémie Dimino wrote:
> Le Fri, 14 Sep 2012 15:53:24 +0200,
> Romain Bardou <romain.bardou@inria.fr> a écrit :
> 
> >    open Unix
> >    let address = "xxx.xxx.xxx.xxx" in (* some IP for IPv4 *)
> >    let port = 9543 in
> >    let fd = socket PF_INET SOCK_STREAM 0 in
> >    set_nonblock fd;
> >    connect fd (ADDR_INET (Unix.inet_addr_of_string address, port))
> 
> If the socket is in non-blocking mode and connect blocks, then you get
> a Unix.EWOULDBLOCK error. According to the MSDN documentation, if
> connect fails with EWOULDBLOCK, you have to wait for the socket to
> become writeable then call connect again which will fail with EISCONN
> if the connection succeeded.

This is not quite what I can read in the MSDN documentation...

  "[...] it is not recommended that applications use multiple calls to
   connect to detect connection completion. If they do, they must be
   prepared to handle WSAEINVAL and WSAEWOULDBLOCK error values the
   same way that they handle WSAEALREADY, to assure robust operation"

You should use Unix.getsockopt_error (just like under Unix) to check
for errors when the socket becomes writable, rather than call connect
again.

-- Jérôme