NN_PUBSUB(7) nanomsg manual NN_PUBSUB(7)NAMEnn_pubsub - publish/subscribe scalability protocol
SYNOPSIS
#include <nanomsg/nn.h>
#include <nanomsg/pubsub.h>
DESCRIPTION
Broadcasts messages to multiple destinations.
Messages are sent from NN_PUB sockets and will only be received by
NN_SUB sockets that have subscribed to the matching topic. Topic is an
arbitrary sequence of bytes at the beginning of the message body. The
NN_SUB socket will determine whether a message should be delivered to
the user by comparing the subscribed topics (using NN_SUB_SUBSCRIBE on
a full SUB socket) to the bytes initial bytes in the incomming message,
up to the size of the topic.
nn_setsockopt (s, NN_SUB, NN_SUB_SUBSCRIBE, "Hello", 5);
Will match any message with intial 5 bytes being "Hello", for example,
message "Hello, World!" will match.
Topic with zero length matches any message.
If the socket is subscribed to multiple topics, message matching any of
them will be delivered to the user.
Since the filtering is performed on the Subscriber side, all the
messages from Publisher will be sent over the transport layer.
The entire message, including the topic, is delivered to the user.
Socket Types
NN_PUB
This socket is used to distribute messages to multiple
destinations. Receive operation is not defined.
NN_SUB
Receives messages from the publisher. Only messages that the socket
is subscribed to are received. When the socket is created there are
no subscriptions and thus no messages will be received. Send
operation is not defined on this socket.
Socket Options
NN_SUB_SUBSCRIBE
Defined on full SUB socket. Subscribes for a particular topic. Type
of the option is string. A single NN_SUB socket can handle multiple
subscriptions.
NN_SUB_UNSUBSCRIBE
Defined on full SUB socket. Unsubscribes from a particular topic.
Type of the option is string.
EXAMPLE
int pub = nn_socket (AF_SP, NN_PUB);
int sub = nn_socket (AF_SP, NN_SUB);
int nbytes;
void *buf = NULL;
nn_setsockopt (sub, NN_SUB, NN_SUB_SUBSCRIBE, "foo", 3);
nn_setsockopt (sub, NN_SUB, NN_SUB_SUBSCRIBE, "bar", 3);
nbytes = nn_send (pub, "foo|Hello!", 10);
assert(nbytes == 10);
nbytes = nn_recv (sub, &buf, NN_MSG, 0);
assert (nbytes == 10);
nn_freemsg (buf);
nbytes = nn_send (pub, "baz|World!", 10);
/* Message is not delivered because if matches no subscription. */
nbytes = nn_recv(sub, &buf, NN_MSG, 0);
SEE ALSOnn_bus(7)nn_reqrep(7)nn_pipeline(7)nn_survey(7)nn_pair(7)nanomsg(7)AUTHORS
Martin Sustrik <sustrik@250bpm.com[1]>
NOTES
1. sustrik@250bpm.com
mailto:sustrik@250bpm.com
nanomsg Unknown 12/23/2015 NN_PUBSUB(7)
