zmq_send(3)

1ZMQ_SEND(3)                       0MQ Manual                       ZMQ_SEND(3)
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NAME

6       zmq_send - send a message part on a socket
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SYNOPSIS

9       int zmq_send (void *socket, const void *buf, size_t len, int flags);
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DESCRIPTION

12       The zmq_send() function shall queue a message created from the buffer
13       referenced by the buf and len arguments. The flags argument is a
14       combination of the flags defined below:
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16       ZMQ_DONTWAIT
17           For socket types (DEALER, PUSH) that block (either with
18           ZMQ_IMMEDIATE option set and no peer available, or all peers having
19           full high-water mark), specifies that the operation should be
20           performed in non-blocking mode. If the message cannot be queued on
21           the socket, the zmq_send() function shall fail with errno set to
22           EAGAIN.
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24       ZMQ_SNDMORE
25           Specifies that the message being sent is a multi-part message, and
26           that further message parts are to follow. Refer to the section
27           regarding multi-part messages below for a detailed description.
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29           Note
30           A successful invocation of zmq_send() does not indicate that the
31           message has been transmitted to the network, only that it has been
32           queued on the socket and 0MQ has assumed responsibility for the
33           message.
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35   Multi-part messages
36       A 0MQ message is composed of 1 or more message parts. 0MQ ensures
37       atomic delivery of messages: peers shall receive either all message
38       parts of a message or none at all. The total number of message parts is
39       unlimited except by available memory.
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41       An application that sends multi-part messages must use the ZMQ_SNDMORE
42       flag when sending each message part except the final one.
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RETURN VALUE

45       The zmq_send() function shall return number of bytes in the message if
46       successful. Otherwise it shall return -1 and set errno to one of the
47       values defined below.
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ERRORS

50       EAGAIN
51           Non-blocking mode was requested and the message cannot be sent at
52           the moment.
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54       ENOTSUP
55           The zmq_send() operation is not supported by this socket type.
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57       EINVAL
58           The sender tried to send multipart data, which the socket type does
59           not allow.
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61       EFSM
62           The zmq_send() operation cannot be performed on this socket at the
63           moment due to the socket not being in the appropriate state. This
64           error may occur with socket types that switch between several
65           states, such as ZMQ_REP. See the messaging patterns section of
66           zmq_socket(3) for more information.
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68       ETERM
69           The 0MQ context associated with the specified socket was
70           terminated.
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72       ENOTSOCK
73           The provided socket was invalid.
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75       EINTR
76           The operation was interrupted by delivery of a signal before the
77           message was sent.
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79       EHOSTUNREACH
80           The message cannot be routed.
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EXAMPLE

83       Sending a multi-part message.
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85           /* Send a multi-part message consisting of three parts to socket */
86           rc = zmq_send (socket, "ABC", 3, ZMQ_SNDMORE);
87           assert (rc == 3);
88           rc = zmq_send (socket, "DEFGH", 5, ZMQ_SNDMORE);
89           assert (rc == 5);
90           /* Final part; no more parts to follow */
91           rc = zmq_send (socket, "JK", 2, 0);
92           assert (rc == 2);
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AUTHORS

99       This page was written by the 0MQ community. To make a change please
100       read the 0MQ Contribution Policy at
101       http://www.zeromq.org/docs:contributing.
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1050MQ 4.3.4                         01/21/2023                       ZMQ_SEND(3)