1ZMQ_MSG_RECV(3) 0MQ Manual ZMQ_MSG_RECV(3)
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6 zmq_msg_recv - receive a message part from a socket
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9 int zmq_msg_recv (zmq_msg_t *msg, void *socket, int flags);
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12 The zmq_msg_recv() function is identical to zmq_recvmsg(3), which shall
13 be deprecated in future versions. zmq_msg_recv() is more consistent
14 with other message manipulation functions.
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16 The zmq_msg_recv() function shall receive a message part from the
17 socket referenced by the socket argument and store it in the message
18 referenced by the msg argument. Any content previously stored in msg
19 shall be properly deallocated. If there are no message parts available
20 on the specified socket the zmq_msg_recv() function shall block until
21 the request can be satisfied. The flags argument is a combination of
22 the flags defined below:
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24 ZMQ_DONTWAIT
25 Specifies that the operation should be performed in non-blocking
26 mode. If there are no messages available on the specified socket,
27 the zmq_msg_recv() function shall fail with errno set to EAGAIN.
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29 Multi-part messages
30 A 0MQ message is composed of 1 or more message parts. Each message part
31 is an independent zmq_msg_t in its own right. 0MQ ensures atomic
32 delivery of messages: peers shall receive either all message parts of a
33 message or none at all. The total number of message parts is unlimited
34 except by available memory.
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36 An application that processes multi-part messages must use the
37 ZMQ_RCVMORE zmq_getsockopt(3) option after calling zmq_msg_recv() to
38 determine if there are further parts to receive.
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41 The zmq_msg_recv() function shall return number of bytes in the message
42 if successful. Otherwise it shall return -1 and set errno to one of the
43 values defined below.
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46 EAGAIN
47 Either the timeout set via the socket-option ZMQ_RCVTIMEO (see
48 zmq_setsockopt(3)) has been reached (flag ZMQ_DONTWAIT not set)
49 without being able to read a message from the socket or there are
50 no messages available at the moment (flag ZMQ_DONTWAIT set) and the
51 operation would block.
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53 ENOTSUP
54 The zmq_msg_recv() operation is not supported by this socket type.
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56 EFSM
57 The zmq_msg_recv() operation cannot be performed on this socket at
58 the moment due to the socket not being in the appropriate state.
59 This error may occur with socket types that switch between several
60 states, such as ZMQ_REP. See the messaging patterns section of
61 zmq_socket(3) for more information.
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63 ETERM
64 The 0MQ context associated with the specified socket was
65 terminated.
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67 ENOTSOCK
68 The provided socket was invalid.
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70 EINTR
71 The operation was interrupted by delivery of a signal before a
72 message was available.
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74 EFAULT
75 The message passed to the function was invalid.
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78 Receiving a message from a socket.
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80 /* Create an empty 0MQ message */
81 zmq_msg_t msg;
82 int rc = zmq_msg_init (&msg);
83 assert (rc == 0);
84 /* Block until a message is available to be received from socket */
85 rc = zmq_msg_recv (&msg, socket, 0);
86 assert (rc != -1);
87 /* Release message */
88 zmq_msg_close (&msg);
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90 Receiving a multi-part message.
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92 int more;
93 size_t more_size = sizeof (more);
94 do {
95 /* Create an empty 0MQ message to hold the message part */
96 zmq_msg_t part;
97 int rc = zmq_msg_init (&part);
98 assert (rc == 0);
99 /* Block until a message is available to be received from socket */
100 rc = zmq_msg_recv (&part, socket, 0);
101 assert (rc != -1);
102 /* Determine if more message parts are to follow */
103 rc = zmq_getsockopt (socket, ZMQ_RCVMORE, &more, &more_size);
104 assert (rc == 0);
105 zmq_msg_close (&part);
106 } while (more);
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110 zmq_recv(3) zmq_send(3) zmq_msg_send(3) zmq_getsockopt(3)
111 zmq_setsockopt(3) zmq_socket(7) zmq(7)
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114 This page was written by the 0MQ community. To make a change please
115 read the 0MQ Contribution Policy at
116 http://www.zeromq.org/docs:contributing.
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1200MQ 4.3.4 01/30/2021 ZMQ_MSG_RECV(3)