Socket question

Socket question

[Rong.Zhou]

Hi,

Can anyone tell me if there is a way in OCaml to *reliably* force a TCP
socket to send out its buffered messages? I noticed that flushing the
corresponding output channel of the socket does not *necessarily* cause
the message to be sent. I know in C/C++ one can use the "TCP_NODELAY"
socket option to solve this problem, but I couldn't find anything in
OCaml that does this. I'd appreciate if someone can give me some
pointers.

Thanks,
Rong

Re: Socket question

[Vincenzo Ciancia]

Rong.Zhou@parc.com wrote:

> Can anyone tell me if there is a way in OCaml to *reliably* force a TCP
> socket to send out its buffered messages? I noticed that flushing the
> corresponding output channel of the socket does not *necessarily* cause
> the message to be sent. I know in C/C++ one can use the "TCP_NODELAY"
> socket option to solve this problem, but I couldn't find anything in
> OCaml that does this. I'd appreciate if someone can give me some
> pointers.

I don't have the time to deepen my knowledge of TCP sockets, but I think
that since they are file descriptors, you can (unsafely) cast a ocaml file
descriptor to an int in C land, and then set the option from C. 

Basically, you have to create an external function, written in C, similar to

value do_stuff_using_file_descr(value fd)
{
  int ifd=Int_val(fd);

  /* use ifd and set options as needed */

  return(Val_unit);
}

and then bind it in ocaml


external do_stuff_using_file_descr : Unix.file_descr -> unit =
"do_stuff_using_file_descr"

Find more information at

http://caml.inria.fr/pub/docs/manual-ocaml/manual032.html

Try that and see if it works. It should work under linux, don't know if on
windows or osx an ocaml file descriptor carries more information than just
the C file descriptor.

Vincenzo


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