nng_sub(7)

SYNOPSIS

#include <nng/protocol/pubsub/pubsub.h>
+
+#define NNG_PROTO_SUB_V0 33
+#define NNG_PROTO_SUB NNG_PROTO_SUB_V0
+
+int nng_sub_open(nng_socket *s);
+int nng_sub0_open (nng_socket *s);

DESCRIPTION

The nng_sub protocol is one half of a publisher/subscriber pattern. +In this pattern, a publisher sends data, which is broadcast to all +subscribers. The subscribing applications only see the data to which +they have subscribed.

The nng_sub protocol is the subscriber side, and the +nng_pub(7) protocol is the publisher side.

+ + + + + +

+ +	+In this implementation, the publisher delivers all messages to all +subscribers. The subscribers maintain their own subscriptions, and filter +them locally. Thus, this pattern should not be used in an attempt to +reduce bandwidth consumption. +

The topics that subscribers subscribe to is just the first part of +the message body. Applications should construct their messages +accordingly.

Socket Operations

The nng_sub_open() call creates a subscriber socket. This socket +may be used to receive messages, but is unable to send them. Attempts +to send messages will result in NNG_ENOTSUP.

Protocol Versions

Only version 0 of this protocol is supported. (At the time of writing, +no other versions of this protocol have been defined.)

Protocol Options

The following protocol-specific options are available.

NNG_OPT_SUB_SUBSCRIBE

This option registers a topic that the subscriber is interested in. +The option is write-only, and takes an array of bytes, of arbitrary size. +Each incoming message is checked against the list of subscribed topics. +If the body begins with the entire set of bytes in the topic, then the +message is accepted. If no topic matches, then the message is +discarded.

+ + + + + +

+ +	+To receive all messages, an empty topic (zero length) can be used. +

NNG_OPT_SUB_UNSUBSCRIBE

This option, also read-only, removes a topic from the subscription list. +Note that if the topic was not previously subscribed to with +NNG_OPT_SUB_SUBSCRIBE then an NNG_ENOENT error will result.

Protocol Headers

The nng_sub protocol has no protocol-specific headers.

AUTHORS

Garrett D’Amore

COPYRIGHT

This document is supplied under the terms of the +MIT License.

nng_sub(7) Manual Page

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