[erlang-questions] inet_db:lookup_socket/1 failing for gen_tcp:controlling_process with mochiweb socket server

[Paul Oliver]

Hi all,

I have a curious bug that I've tracked down to a call to gen_tcp:controlling_process.  From the stack trace (simple example reproduced below) it seems that the port in question definitely exists, but the call to inet_db:lookup fails.  Has anyone seen this before or got any advice?

Thanks!
Paul.

Erlang (BEAM) emulator version 5.6.5 [source] [async-threads:0] [kernel-poll:false]

Eshell V5.6.5  (abort with ^G)
1> mochiweb_socket_server:start( [{ip, "127.0.0.1"}, {loop, {connection, start}}, {name, badger}, {port, 8888}]).
{ok,<0.32.0>}
2> Sock = gen_tcp:connect('127.0.0.1', 8888,  [binary, {packet, line}, {nodelay, true}], 3000000).
{ok,#Port<0.496>}
3> gen_tcp:controlling_process(Sock, self()).

=ERROR REPORT==== 24-Nov-2008::20:59:12 ===
** Generic server badger terminating
** Last message in was {'EXIT',<0.30.0>,
                           {function_clause,
                               [{inet_db,lookup_socket,[{ok,#Port<0.496>}]},
                                {gen_tcp,controlling_process,2},
                                {erl_eval,do_apply,5},
                                {shell,exprs,6},
                                {shell,eval_exprs,6},
                                {shell,eval_loop,3}]}}
** When Server state == {mochiweb_socket_server,8888,
                            {connection,start},
                            {local,badger},
                            2047,
                            {127,0,0,1},
                            #Port<0.488>,<0.37.0>,30}
** Reason for termination ==
** {function_clause,[{inet_db,lookup_socket,[{ok,#Port<0.496>}]},
                     {gen_tcp,controlling_process,2},
                     {erl_eval,do_apply,5},
                     {shell,exprs,6},
                     {shell,eval_exprs,6},
                     {shell,eval_loop,3}]}
** exception exit: function_clause
     in function  inet_db:lookup_socket/1
        called as inet_db:lookup_socket({ok,#Port<0.496>})
     in call from gen_tcp:controlling_process/2
4>

[Paul Oliver]

On Mon, Nov 24, 2008 at 10:18 PM, Matthias Lang <matt...@corelatus.se> wrote:

On Monday, November 24, Paul Oliver wrote:
> Hi all,
>
> I have a curious bug that I've tracked down to a call to
> gen_tcp:controlling_process.  From the stack trace (simple example
> reproduced below) it seems that the port in question definitely exists, but
> the call to inet_db:lookup fails.  Has anyone seen this before or got any
> advice?

This seems too obvious to be your real problem, but just in case,
the second command isn't handling the return correctly. You probably
meant:

{ok, Sock} = gen_tcp:connect(...

Matt

Hi Matt,

Ah yes.  Thanks for pointing that out!  Yes, seems fine now:

1> mochiweb_socket_server:start( [{ip, "127.0.0.1"}, {loop, {connection, start}}, {name, badger}, {port, 8888}]).
{ok,<0.32.0>}

2> {ok, Sock} = gen_tcp:connect('127.0.0.1', 8888,  [binary, {packet, line}, {nodelay, true}], 3000000).
{ok,#Port<0.496>}
3> Sock.
#Port<0.496>
4> gen_tcp:controlling_process(Sock, self()).
ok
5>

Back to the drawing board!

Cheers,
Paul.

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[Matthias Lang]

On Monday, November 24, Paul Oliver wrote:

> Hi all,
>
> I have a curious bug that I've tracked down to a call to
> gen_tcp:controlling_process. From the stack trace (simple example
> reproduced below) it seems that the port in question definitely exists, but
> the call to inet_db:lookup fails. Has anyone seen this before or got any
> advice?

This seems too obvious to be your real problem, but just in case,

the second command isn't handling the return correctly. You probably
meant:

{ok, Sock} = gen_tcp:connect(...

Matt

>

> _______________________________________________