Re: [Caml-list] Error binding socket

[Maurizio Colucci <maurizio.colucci@gmail.com>]

Thank you, that's exactly the answer I was looking for!

2005/11/9, Gerd Stolpmann <info@gerd-stolpmann.de>:
> Am Mittwoch, den 09.11.2005, 13:33 +0100 schrieb Maurizio Colucci:
> > Hi there. For my free tennis game (http://freetennis.sf.net), I get an
> > error binding the socket to a port. (Unix_error 50, "bind"). The error
> > description is "address already in use".
> >
> > This error only happens the *second* time I start the program. It is
> > as if the port had not been freed and were still in use. The system is
> > GNU/Linux Ubuntu Breezy.
> >
> > However, if I wait about 1minute, or I start the program specifying a
> > different port, the problem does not happen. It is as if Linux were
> > freeing the port with a delay.
>
> This is the default behaviour: Linux (and all other OS, too) has this
> delay to ensure that pending connection attempts are properly reset.
> This is reasonable for anonymous ports, but not for well-known service
> ports. You can disable this with the socket option REUSEADDR.
>
> Gerd
>
> >
> > At first glance, I thought I was not using Unix.close or Unix.socket
> > correctly, but this does not seem to be the case.
> >
> > The code is freely available, however here is the relevant part of the code:
> >
> > (* Here is the socket initialization phase, for both client and server: *)
> >
> >             let serverData =
> >                 let rec tryToConnectNTimes n ~soc ~inet_a ~port=
> >                     try
> >                         Unix.connect  soc (Unix.ADDR_INET  (inet_a, port) )
> >                     with Unix.Unix_error _ ->
> >                         if n = 0 then
> >                             raise CouldNotConnectToServer
> >                         else
> >                             ( print_endline ( "The server is down. Retrying " ^
> > string_of_int (n-1) ^ " times.");
> >                               Unix.sleep 1;
> >                               tryToConnectNTimes (n-1) ~soc ~inet_a ~port )
> >                 in
> >                 if !server  then
> >                     let soc = Unix.socket Unix.PF_INET Unix.SOCK_STREAM 0 in
> >                     (
> >                         (try
> >                             Unix.bind soc (Unix.ADDR_INET (Unix.inet_addr_any, !port))
> >                         with Unix.Unix_error (err, _, _) ->
> >                             (print_endline ("Error: " ^(Unix.error_message err) ^ ". This
> > is a known bug. Please wait a few seconds or simply change the port
> > number with the -port option");
> >                              exit 0 ));
> >                         Unix.listen soc 5;
> >                         print_endline "waiting for client to connect...";
> >                         let clientSocket, _ = Unix.accept soc in
> >                         Server ( (soc, clientSocket), Unix.in_channel_of_descr
> > clientSocket, Unix.out_channel_of_descr clientSocket)
> >                     )
> >
> >                 else  if 0 != compare !client  ""  then
> >                     let soc = Unix.socket Unix.PF_INET Unix.SOCK_STREAM 0 in
> >                     let inet_a = Unix.inet_addr_of_string !client in
> >                     print_endline "Connecting to server...";
> >                     ( tryToConnectNTimes 60 ~soc ~inet_a ~port:!port;
> >                       print_endline "Connected to server";
> >                       Client (soc, Unix.in_channel_of_descr  soc, Unix.out_channel_of_descr soc) )
> >                 else
> >                     NeitherServerNorClient
> >             in
> >
> >
> > (*... and here is the socket cleanup code *)
> >
> >             (match serverData with
> >                      (* the rule is to shutdown before you close,
> >                         but this is often automatic. see sockets
> >                         howto.
> >
> >                      *)
> >                  | Server( (sock, clientSocket), inc, outc) ->
> >                        print_endline "Shutting down socket";
> >                        Unix.shutdown clientSocket Unix.SHUTDOWN_ALL ;
> >                        Unix.shutdown sock Unix.SHUTDOWN_ALL ;
> >                        Unix.close clientSocket;
> >                        Unix.close sock;
> >                  | Client ( sock, inc, outc) ->
> >                        print_endline "Shutting down socket";
> >                        Unix.shutdown sock Unix.SHUTDOWN_ALL  ;
> >                        Unix.close sock;
> >
> >                  | NeitherServerNorClient -> ());
> >
> >
> >
> > One doubt I have is the following: in the server code, must I call
> > close on sock or in clientSocket?
> >
> > If I am doing something wrong, could you please tell me. :-) Thank you
> >
> >
> >
> > Maurizio
> >
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> --
> ------------------------------------------------------------
> Gerd Stolpmann * Viktoriastr. 45 * 64293 Darmstadt * Germany
> gerd@gerd-stolpmann.de          http://www.gerd-stolpmann.de
> Telefon: 06151/153855                  Telefax: 06151/997714
> ------------------------------------------------------------
>
>