问题
I am using pub/Sub Socket and currently the server subscribe byte[0] (all topics) while client subscribe byte[16] - a specific header as topic
However, I cannot stop client to subscribe byte[0] which can receive all other messages.
My application is a like a app game which has one single server using ZMQ as connection and many clients have a ZMQ sockets to talk with server.
What pattern or socket I should use in this case?
Thanks
回答1:
" ... cannot stop client to subscribe byte[0] which can receive all other messages."
Stopping a "subscribe to all" mode of the SUB client
For the ZMQ PUB
/SUB
Formal Communication Pattern archetype, the SUB
client has to submit it's subscription request ( via zmq_setsockopt()
).
PUB
-side ( a Game Server ) has got no option to do that from it's side.
There is no-subscription state right on a creation of a new SUB
socket, thus an absolutely restrictive filter, thas no message pass through. ( For furhter details on methods for SUBSCRIBE
/ UNSUBSCRIBE
ref. below )
ZeroMQ specification details setting for this:
int zmq_setsockopt ( void *socket,
int option_name,
const void *option_value,
size_t option_len
);
Caution: only ZMQ_SUBSCRIBE
ZMQ_UNSUBSCRIBE
ZMQ_LINGER
take effect immediately,
other options are active only for subsequent socket bind/connects.
ZMQ_SUBSCRIBE
: Establish message filter
The ZMQ_SUBSCRIBE
option shall establish a new message filter on a ZMQ_SUB
socket. Newly created ZMQ_SUB
sockets shall filter out all incoming messages, therefore you should call this option to establish an initial message filter.
An empty option_value
of length zero shall subscribe to all incoming messages.
A non-empty option_value
shall subscribe to all messages beginning with the specified prefix.
Multiple filters may be attached to a single ZMQ_SUB
socket, in which case a message shall be accepted if it matches at least one filter.
ZMQ_UNSUBSCRIBE
: Remove message filter
The ZMQ_UNSUBSCRIBE
option shall remove an existing message filter on a ZMQ_SUB
socket. The filter specified must match an existing filter previously established with the ZMQ_SUBSCRIBE
option. If the socket has several instances of the same filter attached the ZMQ_UNSUBSCRIBE
option shall remove only one instance, leaving the rest in place and functional.
How to enforce an ad-hoc, server-dictated, ZMQ_SUBSCRIBE restrictions?
This is possible via extending the messaging layer and adding a control-mode socket, that will carry server-initiated settings for the client ZMQ_SUB
messages filtering.
Upon receiving a new, the server-dictated, ZMQ_SUBSCRIBE
/ZMQ_UNSUBSCRIBE
setting, the ZMQ_SUB
client side code will simply handle that request and add zmq_setsockopt()
accordingly.
FSA-driven grammars for this approach are rich of further possibilites, so will allow any Game Server / Game Community to smoothly go this way.
What pattern or socket I should use?
ZeroMQ is rather a library of LEGO-style elements to get assembled into a bigger picture.
Expecting such a smart library to have a one-size-fits-all ninja-element is on a closer look an oxymoron.
So, to avoid a "Never-ending-story" of adding "although this ... and also that ..."
Review all requirements and & list features for the end-to-end scaleable solution,
Design a messaging concept & validate it to meet all the listed requirements & cover all features in [1]
Implement [2]
Test [3] & correct it for meeting 1:1 the end-to-end specification [1]
Enjoy it. You have done it end-to-end right.
来源:https://stackoverflow.com/questions/25696501/can-zmq-publish-message-to-specific-client-by-pub-sub-socket