zmq_send(3)
===========


NAME
----
zmq_send - send a message part on a socket


SYNOPSIS
--------
*int zmq_send (void '*socket', void '*buf', size_t 'len', int 'flags');*


DESCRIPTION
-----------
The _zmq_send()_ function shall queue a message created from the buffer
referenced by the 'buf' and 'len' arguments. The 'flags' argument is
a combination of the flags defined below:

*ZMQ_DONTWAIT*::
Specifies that the operation should be performed in non-blocking mode. If the
message cannot be queued on the 'socket', the _zmq_send()_ 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()_ 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()_ 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()_ operation is not supported by this socket type.
*EFSM*::
The _zmq_send()_ 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 linkzmq: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.


EXAMPLE
-------
.Sending a multi-part message
----
/* Send a multi-part message consisting of three parts to socket */
rc = zmq_send (socket, "ABC", 3, ZMQ_SNDMORE);
assert (rc == 3);
rc = zmq_send (socket, "DEFGH", 5, ZMQ_SNDMORE);
assert (rc == 5);
/* Final part; no more parts to follow */
rc = zmq_send (socket, "JK", 2, 0);
assert (rc == 2);
----

SEE ALSO
--------
linkzmq:zmq_sendmsg[3]
linkzmq:zmq_recv[3]
linkzmq:zmq_recvmsg[3]
linkzmq:zmq_socket[7]
linkzmq:zmq[7]


AUTHORS
-------
This 0MQ manual page was written by Martin Sustrik <sustrik@250bpm.com> and
Martin Lucina <mato@kotelna.sk>, and Pieter Hintjens <ph@imatix.com>.
