'\" t
.\"     Title: zmq_recv
.\"    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_RECV" "3" "09/06/2020" "0MQ 4\&.3\&.1" "0MQ Manual"
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.SH "NAME"
zmq_recv \- receive a message part from a socket
.SH "SYNOPSIS"
.sp
\fBint zmq_recv (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_recv()\fR function shall receive a message from the socket referenced by the \fIsocket\fR argument and store it in the buffer referenced by the \fIbuf\fR argument\&. Any bytes exceeding the length specified by the \fIlen\fR argument shall be truncated\&. If there are no messages available on the specified \fIsocket\fR the \fIzmq_recv()\fR function shall block until the request can be satisfied\&. The \fIflags\fR argument is a combination of the flags defined below: The \fIbuf\fR argument may be null if len is zero\&.
.PP
\fBZMQ_DONTWAIT\fR
.RS 4
Specifies that the operation should be performed in non\-blocking mode\&. If there are no messages available on the specified
\fIsocket\fR, the
\fIzmq_recv()\fR
function shall fail with
\fIerrno\fR
set to EAGAIN\&.
.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 processes multi\-part messages must use the \fIZMQ_RCVMORE\fR \fBzmq_getsockopt\fR(3) option after calling \fIzmq_recv()\fR to determine if there are further parts to receive\&.
.SH "RETURN VALUE"
.sp
The \fIzmq_recv()\fR function shall return number of bytes in the message if successful\&. Note that the value can exceed the value of the \fIlen\fR parameter in case the message was truncated\&. If not successful the function 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 no messages are available at the moment\&.
.RE
.PP
\fBENOTSUP\fR
.RS 4
The
\fIzmq_recv()\fR
operation is not supported by this socket type\&.
.RE
.PP
\fBEFSM\fR
.RS 4
The
\fIzmq_recv()\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 a message was available\&.
.RE
.SH "EXAMPLE"
.PP
\fBReceiving a message from a socket\fR. 
.sp
.if n \{\
.RS 4
.\}
.nf
char buf [256];
nbytes = zmq_recv (socket, buf, 256, 0);
assert (nbytes != \-1);
.fi
.if n \{\
.RE
.\}
.sp
.SH "SEE ALSO"
.sp
\fBzmq_send\fR(3) \fBzmq_getsockopt\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[]\&.