'\" t
.\"     Title: zmq_send_const
.\"    Author: [see the "AUTHORS" section]
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: 09/06/2020
.\"    Manual: 0MQ Manual
.\"    Source: 0MQ 4.3.1
.\"  Language: English
.\"
.TH "ZMQ_SEND_CONST" "3" "09/06/2020" "0MQ 4\&.3\&.1" "0MQ Manual"
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.SH "NAME"
zmq_send_const \- send a constant\-memory message part on a socket
.SH "SYNOPSIS"
.sp
\fBint zmq_send_const (void \fR\fB\fI*socket\fR\fR\fB, void \fR\fB\fI*buf\fR\fR\fB, size_t \fR\fB\fIlen\fR\fR\fB, int \fR\fB\fIflags\fR\fR\fB);\fR
.SH "DESCRIPTION"
.sp
The \fIzmq_send_const()\fR function shall queue a message created from the buffer referenced by the \fIbuf\fR and \fIlen\fR arguments\&. The message buffer is assumed to be constant\-memory and will therefore not be copied or deallocated in any way\&. The \fIflags\fR argument is a combination of the flags defined below:
.PP
\fBZMQ_DONTWAIT\fR
.RS 4
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
\fIsocket\fR, the
\fIzmq_send_const()\fR
function shall fail with
\fIerrno\fR
set to EAGAIN\&.
.RE
.PP
\fBZMQ_SNDMORE\fR
.RS 4
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\&.
.RE
.if n \{\
.sp
.\}
.RS 4
.it 1 an-trap
.nr an-no-space-flag 1
.nr an-break-flag 1
.br
.ps +1
\fBNote\fR
.ps -1
.br
.sp
A successful invocation of \fIzmq_send_const()\fR does not indicate that the message has been transmitted to the network, only that it has been queued on the \fIsocket\fR and 0MQ has assumed responsibility for the message\&.
.sp .5v
.RE
.SS "Multi\-part messages"
.sp
A 0MQ message is composed of 1 or more message parts\&. 0MQ ensures atomic delivery of messages: peers shall receive either all \fImessage parts\fR of a message or none at all\&. The total number of message parts is unlimited except by available memory\&.
.sp
An application that sends multi\-part messages must use the \fIZMQ_SNDMORE\fR flag when sending each message part except the final one\&.
.SH "RETURN VALUE"
.sp
The \fIzmq_send_const()\fR function shall return number of bytes in the message if successful\&. Otherwise it shall return \-1 and set \fIerrno\fR to one of the values defined below\&.
.SH "ERRORS"
.PP
\fBEAGAIN\fR
.RS 4
Non\-blocking mode was requested and the message cannot be sent at the moment\&.
.RE
.PP
\fBENOTSUP\fR
.RS 4
The
\fIzmq_send_const()\fR
operation is not supported by this socket type\&.
.RE
.PP
\fBEFSM\fR
.RS 4
The
\fIzmq_send_const()\fR
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
\fImessaging patterns\fR
section of
\fBzmq_socket\fR(3)
for more information\&.
.RE
.PP
\fBETERM\fR
.RS 4
The 0MQ
\fIcontext\fR
associated with the specified
\fIsocket\fR
was terminated\&.
.RE
.PP
\fBENOTSOCK\fR
.RS 4
The provided
\fIsocket\fR
was invalid\&.
.RE
.PP
\fBEINTR\fR
.RS 4
The operation was interrupted by delivery of a signal before the message was sent\&.
.RE
.PP
\fBEHOSTUNREACH\fR
.RS 4
The message cannot be routed\&.
.RE
.SH "EXAMPLE"
.PP
\fBSending a multi-part message\fR. 
.sp
.if n \{\
.RS 4
.\}
.nf
/* 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);
.fi
.if n \{\
.RE
.\}
.sp
.SH "SEE ALSO"
.sp
\fBzmq_send\fR(3) \fBzmq_recv\fR(3) \fBzmq_socket\fR(7) \fBzmq\fR(7)
.SH "AUTHORS"
.sp
This page was written by the 0MQ community\&. To make a change please read the 0MQ Contribution Policy at \m[blue]\fBhttp://www\&.zeromq\&.org/docs:contributing\fR\m[]\&.