[zeromq-dev] subscription format changed in 0MQ/2.0 trunk

Martin Sustrik sustrik at 250bpm.com
Mon Dec 28 21:43:00 CET 2009

Hi all,

Those using 0MQ/2.0 from trunk should note that the subscription format 
have changed as previously announced here:


Now the subscription (ZMQ_SUBSCRIBE socket option) is simply a prefix 
that message has to have not to be filtered out. There's no need for * 
symbol anymore.


Subscribe for all messages (empty prefix):

zmq_setsockopt (s, ZMQ_SUBSCRIBE, "", 0);

Subscribe for all messages starting with "ABC":

zmq_setsockopt (s, ZMQ_SUBSCRIBE, "ABC", 3);

Subscribe for all messages starting with "ABC" followed by binary zero 
as a delimiter:

zmq_setsockopt (s, ZMQ_SUBSCRIBE, "ABC\x00", 4);


1. Message doesn't have to follow any predefined format (before this 
change message was required to start with size-prefixed topic string).

2. The size of the topic/subscription string is unbound (before it was 
bound to at most 255 bytes).

3. Asterisk is considered a normal character (before it was reserved as 
a wildcard).


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