ZMQ_SENDMSG(3) 0MQ Manual ZMQ_SENDMSG(3)
NAME
zmq_sendmsg - send a message part on a socket
SYNOPSIS
int zmq_sendmsg (void *socket, zmq_msg_t *msg, int flags);
DESCRIPTION
The zmq_sendmsg() function shall queue the message referenced by the
msg argument to be sent to the socket referenced by the socket
argument. The flags argument is a combination of the flags defined
below:
ZMQ_DONTWAIT
For socket types (DEALER, PUSH) that block (either with
ZMQ_IMMEDIATE option set and no peer available, or all peers having
full high-water mark), specifies that the operation should be
performed in non-blocking mode. If the message cannot be queued on
the socket, the zmq_sendmsg() function shall fail with errno set to
EAGAIN.
ZMQ_SNDMORE
Specifies that the message being sent is a multi-part message, and
that further message parts are to follow. Refer to the section
regarding multi-part messages below for a detailed description.
The zmq_msg_t structure passed to zmq_sendmsg() is nullified during the
call. If you want to send the same message to multiple sockets you have
to copy it (e.g. using zmq_msg_copy()).
Note
A successful invocation of zmq_sendmsg() does not indicate that the
message has been transmitted to the network, only that it has been
queued on the socket and 0MQ has assumed responsibility for the
message.
Note
this API method is deprecated in favor of zmq_msg_send(3).
Multi-part messages
A 0MQ message is composed of 1 or more message parts. Each message part
is an independent zmq_msg_t in its own right. 0MQ ensures atomic
delivery of messages: peers shall receive either all message parts of a
message or none at all. The total number of message parts is unlimited
except by available memory.
An application that sends multi-part messages must use the ZMQ_SNDMORE
flag when sending each message part except the final one.
RETURN VALUE
The zmq_sendmsg() function shall return number of bytes in the message
if successful. Otherwise it shall return -1 and set errno to one of the
values defined below.
ERRORS
EAGAIN
Non-blocking mode was requested and the message cannot be sent at
the moment.
ENOTSUP
The zmq_sendmsg() operation is not supported by this socket type.
EINVAL
The sender tried to send multipart data, which the socket type does
not allow.
EFSM
The zmq_sendmsg() operation cannot be performed on this socket at
the moment due to the socket not being in the appropriate state.
This error may occur with socket types that switch between several
states, such as ZMQ_REP. See the messaging patterns section of
zmq_socket(3) for more information.
ETERM
The 0MQ context associated with the specified socket was
terminated.
ENOTSOCK
The provided socket was invalid.
EINTR
The operation was interrupted by delivery of a signal before the
message was sent.
EFAULT
Invalid message.
EHOSTUNREACH
The message cannot be routed.
EXAMPLE
Filling in a message and sending it to a socket.
/* Create a new message, allocating 6 bytes for message content */
zmq_msg_t msg;
int rc = zmq_msg_init_size (&msg, 6);
assert (rc == 0);
/* Fill in message content with 'AAAAAA' */
memset (zmq_msg_data (&msg), 'A', 6);
/* Send the message to the socket */
rc = zmq_sendmsg (socket, &msg, 0);
assert (rc == 6);
Sending a multi-part message.
/* Send a multi-part message consisting of three parts to socket */
rc = zmq_sendmsg (socket, &part1, ZMQ_SNDMORE);
rc = zmq_sendmsg (socket, &part2, ZMQ_SNDMORE);
/* Final part; no more parts to follow */
rc = zmq_sendmsg (socket, &part3, 0);
SEE ALSO
zmq_recv(3) zmq_socket(7) zmq(7)
AUTHORS
This page was written by the 0MQ community. To make a change please
read the 0MQ Contribution Policy at
http://www.zeromq.org/docs:contributing.
0MQ 4.3.4 01/18/2023 ZMQ_SENDMSG(3)
Generated by dwww version 1.15 on Mon Jul 1 07:08:32 CEST 2024.