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Message-ID: <470C2B72.3090704@gmail.com>
Date: Tue, 09 Oct 2007 18:31:30 -0700
From: Reed Wilson <cedilla@gmail.com>
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To: caml-list@yquem.inria.fr
Subject: UDP broadcast from Windows
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X-Spam: no; 0.00; setsockopt:01 printf:01 printf:01 ocaml:01 unix:01 unix:01 defined:02 string:02 string:02 seems:03 let:03 let:03 middle:94 broadcast:92 broadcast:92 

Hi guys!

I'm in the middle of writing a program which does a UDP broadcast, but I 
noticed it doesn't work on Windows. Here's the source:

try (
   let sock = Unix.socket Unix.PF_INET Unix.SOCK_DGRAM 0 in
   Unix.setsockopt sock Unix.SO_BROADCAST true;
   let sent = Unix.sendto sock "ping" 0 4 [] (Unix.ADDR_INET 
((Unix.inet_addr_of_string "255.255.255.255"), 12345)) in
   Printf.printf "Sent %d\n" sent;
) with
   | Unix.Unix_error (x,y,z) -> Printf.printf "%S - %s,%s\n" 
(Unix.error_message x) y z
;;


I noticed that when I force the address by replacing:
Unix.inet_addr_of_string "255.255.255.255"

with:
Obj.magic "\255\255\255\255"

it _seems_ to work fine. I looked around in the OCaml source, and it 
looks like the broadcast address is specifically disallowed unless 
HAS_INET_ATON is defined? Why is this? And am I breaking anything by 
using magic?

Thanks
Reed