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NN_PUBSUB(7)                    nanomsg manual                    NN_PUBSUB(7)

NAME
       nn_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 ALSO
       nn_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)