ZMQ_SEND_CONST(3) 0MQ Manual ZMQ_SEND_CONST(3)NAMEzmq_send_const - send a constant-memory message part on a socket
SYNOPSIS
int zmq_send_const (void *socket, void *buf, size_t len, int flags);
DESCRIPTION
The zmq_send_const() function shall queue a message created from the
buffer referenced by the buf and len arguments. The message buffer is
assumed to be constant-memory and will therefore not be copied or
deallocated in any way. The flags argument is a combination of the
flags defined below:
ZMQ_DONTWAIT
For socket types (DEALER, PUSH) that block when there are no
available peers (or all peers have 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_send_const()
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.
Note
A successful invocation of zmq_send_const() 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.
Multi-part messages
A 0MQ message is composed of 1 or more message parts. 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_send_const() 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_send_const() operation is not supported by this socket
type.
EFSM
The zmq_send_const() 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.
EHOSTUNREACH
The message cannot be routed.
EXAMPLE
Sending a multi-part message.
/* Send a multi-part message consisting of three parts to socket */
rc = zmq_send_const (socket, "ABC", 3, ZMQ_SNDMORE);
assert (rc == 3);
rc = zmq_send_const (socket, "DEFGH", 5, ZMQ_SNDMORE);
assert (rc == 5);
/* Final part; no more parts to follow */
rc = zmq_send_const (socket, "JK", 2, 0);
assert (rc == 2);
SEE ALSOzmq_send(3)zmq_recv(3)zmq_socket(7)zmq(7)AUTHORS
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0MQ 4.1.0 08/17/2015 ZMQ_SEND_CONST(3)
