1ZMQ_RECV(3) 0MQ Manual ZMQ_RECV(3)
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6 zmq_recv - receive a message from a socket
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9 int zmq_recv (void *socket, zmq_msg_t *msg, int flags);
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12 The zmq_recv() function shall receive a message from the socket
13 referenced by the socket argument and store it in the message
14 referenced by the msg argument. Any content previously stored in msg
15 shall be properly deallocated. If there are no messages available on
16 the specified socket the zmq_recv() function shall block until the
17 request can be satisfied. The flags argument is a combination of the
18 flags defined below:
19 ZMQ_NOBLOCK
21 Specifies that the operation should be performed in non-blocking
22 mode. If there are no messages available on the specified socket,
23 the zmq_recv() function shall fail with errno set to EAGAIN.
24 Multi-part messages
26 A 0MQ message is composed of 1 or more message parts; each message part
27 is an independent zmq_msg_t in its own right. 0MQ ensures atomic
28 delivery of messages; peers shall receive either all message parts of a
29 message or none at all.
30 The total number of message parts is unlimited.
32 An application wishing to determine if a message is composed of
34 multiple parts does so by retrieving the value of the ZMQ_RCVMORE
35 socket option on the socket it is receiving the message from. If there
36 are no message parts to follow, or if the message is not composed of
37 multiple parts, ZMQ_RCVMORE shall report a value of zero. Otherwise,
38 ZMQ_RCVMORE shall report a value of 1, indicating that more message
39 parts are to follow.
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42 The zmq_recv() function shall return zero if successful. Otherwise it
43 shall return -1 and set errno to one of the values defined below.
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46 EAGAIN
47 Non-blocking mode was requested and no messages are available at
48 the moment.
49 ENOTSUP
51 The zmq_recv() operation is not supported by this socket type.
52 EFSM
54 The zmq_recv() operation cannot be performed on this socket at the
55 moment due to the socket not being in the appropriate state. This
56 error may occur with socket types that switch between several
57 states, such as ZMQ_REP. See the messaging patterns section of
58 zmq_socket(3) for more information.
59 ETERM
61 The 0MQ context associated with the specified socket was
62 terminated.
63 EFAULT
65 The provided socket was not valid (NULL).
66 EINTR
68 The operation was interrupted by delivery of a signal before a
69 message was available.
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72 Receiving a message from a socket.
73 /* Create an empty 0MQ message */
75 zmq_msg_t msg;
76 int rc = zmq_msg_init (&msg);
77 assert (rc == 0);
78 /* Block until a message is available to be received from socket */
79 rc = zmq_recv (socket, &msg, 0);
80 assert (rc == 0);
81 /* Release message */
82 zmq_msg_close (&msg);
83 Receiving a multi-part message.
85 int64_t more;
87 size_t more_size = sizeof more;
88 do {
89 /* Create an empty 0MQ message to hold the message part */
90 zmq_msg_t part;
91 int rc = zmq_msg_init (&part);
92 assert (rc == 0);
93 /* Block until a message is available to be received from socket */
94 rc = zmq_recv (socket, &part, 0);
95 assert (rc == 0);
96 /* Determine if more message parts are to follow */
97 rc = zmq_getsockopt (socket, ZMQ_RCVMORE, &more, &more_size);
98 assert (rc == 0);
99 zmq_msg_close (&part);
100 } while (more);
101
104 zmq_send(3) zmq_getsockopt(3) zmq_socket(7) zmq(7)
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107 This 0MQ manual page was written by Martin Sustrik
108 <sustrik@250bpm.com[1]> and Martin Lucina <mato@kotelna.sk[2]>.
109
111 1. sustrik@250bpm.com
112 mailto:sustrik@250bpm.com
113 2. mato@kotelna.sk
115 mailto:mato@kotelna.sk
1160MQ 2.1.4 03/30/2011 ZMQ_RECV(3)