1NN_PUBSUB(7)                     nanomsg 1.1.5                    NN_PUBSUB(7)
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NAME

6       nn_pubsub - publish/subscribe scalability protocol
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SYNOPSIS

9       #include <nanomsg/nn.h>
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11       #include <nanomsg/pubsub.h>
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DESCRIPTION

14       Broadcasts messages to multiple destinations.
15
16       Messages are sent from NN_PUB sockets and will only be received by
17       NN_SUB sockets that have subscribed to the matching topic. Topic is an
18       arbitrary sequence of bytes at the beginning of the message body. The
19       NN_SUB socket will determine whether a message should be delivered to
20       the user by comparing the subscribed topics (using NN_SUB_SUBSCRIBE on
21       a full SUB socket) to the bytes initial bytes in the incoming message,
22       up to the size of the topic.
23
24           nn_setsockopt (s, NN_SUB, NN_SUB_SUBSCRIBE, "Hello", 5);
25
26       Will match any message with intial 5 bytes being "Hello", for example,
27       message "Hello, World!" will match.
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29       Topic with zero length matches any message.
30
31       If the socket is subscribed to multiple topics, message matching any of
32       them will be delivered to the user.
33
34       Since the filtering is performed on the Subscriber side, all the
35       messages from Publisher will be sent over the transport layer.
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37       The entire message, including the topic, is delivered to the user.
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39   Socket Types
40       NN_PUB
41           This socket is used to distribute messages to multiple
42           destinations. Receive operation is not defined.
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44       NN_SUB
45           Receives messages from the publisher. Only messages that the socket
46           is subscribed to are received. When the socket is created there are
47           no subscriptions and thus no messages will be received. Send
48           operation is not defined on this socket.
49
50   Socket Options
51       NN_SUB_SUBSCRIBE
52           Defined on full SUB socket. Subscribes for a particular topic. Type
53           of the option is string. A single NN_SUB socket can handle multiple
54           subscriptions.
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56       NN_SUB_UNSUBSCRIBE
57           Defined on full SUB socket. Unsubscribes from a particular topic.
58           Type of the option is string.
59
60   EXAMPLE
61           int pub = nn_socket (AF_SP, NN_PUB);
62           int sub = nn_socket (AF_SP, NN_SUB);
63           int nbytes;
64           void *buf = NULL;
65           char *addr = "inproc://example";
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67           nn_setsockopt (sub, NN_SUB, NN_SUB_SUBSCRIBE, "foo", 3);
68           nn_setsockopt (sub, NN_SUB, NN_SUB_SUBSCRIBE, "bar", 3);
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70           nn_bind(pub, addr);
71           nn_connect(sub, addr);
72
73           nbytes = nn_send (pub, "foo|Hello!", 10);
74           assert(nbytes == 10);
75           nbytes = nn_recv (sub, &buf, NN_MSG, 0);
76           assert (nbytes == 10);
77           nn_freemsg (buf);
78
79           nbytes = nn_send (pub, "baz|World!", 10);
80
81           /* Message is not delivered because if matches no subscription. */
82           nbytes = nn_recv(sub, &buf, NN_MSG, 0);
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SEE ALSO

85       nn_bus(7) nn_reqrep(7) nn_pipeline(7) nn_survey(7) nn_pair(7)
86       nanomsg(7)
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AUTHORS

89       Martin Sustrik <sustrik@250bpm.com>
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93                                  2020-08-24                      NN_PUBSUB(7)
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