[zeromq-dev] XSUB/XPUB proper usage

[Pieter Hintjens]

Either XSUB or SUB can connect to XPUB. With XSUB you have to send the
subscribe / unsubscribe messages yourself. With SUB they're sent by
the socket. In either case the XPUB will detect a dead (X)SUB peer and
generate ubsub messages up to the API.

On Mon, Dec 29, 2014 at 5:08 PM, Kenneth Adam Miller
<kennethadammiller at gmail.com> wrote:
>
> On Mon, Dec 29, 2014 at 11:03 AM, Pieter Hintjens <ph at imatix.com> wrote:
>>
>> On Mon, Dec 29, 2014 at 4:51 PM, Kenneth Adam Miller
>> <kennethadammiller at gmail.com> wrote:
>>
>> > Now my questions: for xpub and xsub do you do the following:
>> >   pub->setsockopt(ZMQ_SUBSCRIBE, "", 0);
>>
>> No, this works only on SUB sockets.
>>
> I meant sub->setsockopt... but now that makes me think- don't I use ZMQ_SUB
> to connect to ZMQ_XPUB?
>
>>
>> > at all? Or does the following handle it completely:
>> >   char *s = "xsubscriptionprefix";
>> >   s[0]='\x01';
>> >   sub->send(s);
>>
>> Yes.
>>
>> > Also is there a need for unsubscription upon closure of sub?
>> > char *s="\x00";
>> > sub->send(s);
>>
>> Not needed at the SUB side at all; it's handled by the PUB socket. (I
>> think, from memory.)
>>
>> -Pieter
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>
>
>
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