[zeromq-dev] zmq_proxy_steerable

Brian Knox briank at talksum.com
Mon Dec 2 15:27:03 CET 2013


I now have terminate, pause and resume working in my fork of czmq.  The last piece I need to do is wrap some portions in #if (ZMQ_VERSION >= foo) calls to make sure I don't break backwards compatibility with previous libzmq versions.

I'm a little fuzzy on the ZMQ_VERSION / MAKE_ZMQ_VERSION macros ... would the proper ZMQ_VERSION for ZMQ_VERSION_MAJOR 4, ZMQ_VERSION_MINOR 1, ZMQ_VERSION_PATCH 0 be "40100"?  eg...

#if (ZMQ_VERSION >= 40100)
...
#else
...

Thanks,
Brian
________________________________________
From: zeromq-dev-bounces at lists.zeromq.org <zeromq-dev-bounces at lists.zeromq.org> on behalf of Pieter Hintjens <ph at imatix.com>
Sent: Sunday, December 01, 2013 2:47 PM
To: ZeroMQ development list
Subject: Re: [zeromq-dev] zmq_proxy_steerable

The usual convention (it's described in the Guide pretty early on) is
to not send or assume trailing null characters.  zstr_send/recv remove
and add the null characters explicitly. Expecting a null in the raw
message data is wrong... and your fix is correct.

On Sun, Dec 1, 2013 at 7:11 PM, Brian Knox <taotetek at gmail.com> wrote:
> So - for fun I patched my local libzmq and changed the length check to not
> take the null terminator into account...
>
> if (msg.size () == 5 && memcmp (msg.data (), "PAUSE", 5) == 0)
>
> ...and now I can send the PAUSE command using zstr_send - so this confirms
> my thought.
>
> Since the least disruptive change now that I understand what's going on is
> just to change my zproxy code to send the full char with terminator using
> zmsg rather than zstr, I'll do that - just following up to my question in
> case this information is useful to others.
>
> Brian
>
>
>
>
> On Sun, Dec 1, 2013 at 10:39 AM, Brian Knox <taotetek at gmail.com> wrote:
>>
>> Hello!
>>
>> I'm working on adding support for zmq_proxy_steerable commands to zproxy
>> in czmq.  I noticed I was getting an invalid proxy command error when trying
>> to send a "PAUSE" command using zstr_send.
>>
>> Taking a look at the libzmq proxy.cpp code ~ line 117 on libzmq head
>> (https://github.com/zeromq/libzmq/blob/master/src/proxy.cpp#L117) , I see:
>>
>> --------------------------------------------------
>> if (msg.size () == 6 && memcmp (msg.data (), "PAUSE", 6) == 0)
>>                 state = paused;
>> ----------------------------------------------------
>>
>> My understanding is that zstr_send (from czmq) does not send the NULL at
>> the end of the string, and zstr_recv adds one (
>> https://github.com/zeromq/czmq/blob/master/src/zstr.c#L68 )
>>
>> While I know libzmq is not czmq - I just want to make sure I understand
>> the libzmq code.  Should I be sending "PAUSE" with a null terminator, and is
>> that why the command check in proxy.cpp is looking for a message size of 6
>> rather than 5?
>>
>> Thanks!
>> Brian
>
>
>
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