'\" t
.\"     Title: zmq_recv
.\"    Author: [see the "AUTHORS" section]
.\" Generator: DocBook XSL Stylesheets v1.75.2 <http://docbook.sf.net/>
.\"      Date: 11/22/2011
.\"    Manual: 0MQ Manual
.\"    Source: 0MQ 2.1.10
.\"  Language: English
.\"
.TH "ZMQ_RECV" "3" "11/22/2011" "0MQ 2\&.1\&.10" "0MQ Manual"
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.SH "NAME"
zmq_recv \- receive a message from a socket
.SH "SYNOPSIS"
.sp
\fBint zmq_recv (void \fR\fB\fI*socket\fR\fR\fB, zmq_msg_t \fR\fB\fI*msg\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 message referenced by the \fImsg\fR argument\&. Any content previously stored in \fImsg\fR shall be properly deallocated\&. 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:
.PP
\fBZMQ_NOBLOCK\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; each message part is an independent \fIzmq_msg_t\fR in its own right\&. 0MQ ensures atomic delivery of messages; peers shall receive either all \fImessage parts\fR of a message or none at all\&.
.sp
The total number of message parts is unlimited\&.
.sp
An application wishing to determine if a message is composed of multiple parts does so by retrieving the value of the \fIZMQ_RCVMORE\fR socket option on the \fIsocket\fR it is receiving the message from\&. If there are no message parts to follow, or if the message is not composed of multiple parts, \fIZMQ_RCVMORE\fR shall report a value of zero\&. Otherwise, \fIZMQ_RCVMORE\fR shall report a value of 1, indicating that more message parts are to follow\&.
.SH "RETURN VALUE"
.sp
The \fIzmq_recv()\fR function shall return zero 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 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
.PP
\fBEFAULT\fR
.RS 4
The message passed to the function was invalid\&.
.RE
.SH "EXAMPLE"
.PP
\fBReceiving a message from a socket\fR. 
.sp
.if n \{\
.RS 4
.\}
.nf
/* Create an empty 0MQ message */
zmq_msg_t msg;
int rc = zmq_msg_init (&msg);
assert (rc == 0);
/* Block until a message is available to be received from socket */
rc = zmq_recv (socket, &msg, 0);
assert (rc == 0);
/* Release message */
zmq_msg_close (&msg);
.fi
.if n \{\
.RE
.\}
.PP
\fBReceiving a multi-part message\fR. 
.sp
.if n \{\
.RS 4
.\}
.nf
int64_t more;
size_t more_size = sizeof more;
do {
    /* Create an empty 0MQ message to hold the message part */
    zmq_msg_t part;
    int rc = zmq_msg_init (&part);
    assert (rc == 0);
    /* Block until a message is available to be received from socket */
    rc = zmq_recv (socket, &part, 0);
    assert (rc == 0);
    /* Determine if more message parts are to follow */
    rc = zmq_getsockopt (socket, ZMQ_RCVMORE, &more, &more_size);
    assert (rc == 0);
    zmq_msg_close (&part);
} while (more);
.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 0MQ manual page was written by Martin Sustrik <\m[blue]\fBsustrik@250bpm\&.com\fR\m[]\&\s-2\u[1]\d\s+2> and Martin Lucina <\m[blue]\fBmato@kotelna\&.sk\fR\m[]\&\s-2\u[2]\d\s+2>\&.
.SH "NOTES"
.IP " 1." 4
sustrik@250bpm.com
.RS 4
\%mailto:sustrik@250bpm.com
.RE
.IP " 2." 4
mato@kotelna.sk
.RS 4
\%mailto:mato@kotelna.sk
.RE