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175 lines
5.2 KiB
175 lines
5.2 KiB
'\" t
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.\" Title: zmq_recvmsg
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.\" Author: [see the "AUTHORS" section]
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.\" Generator: DocBook XSL Stylesheets v1.78.1 <http://docbook.sf.net/>
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.\" Date: 02/18/2017
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.\" Manual: 0MQ Manual
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.\" Source: 0MQ 4.2.2
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.\" Language: English
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.\"
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.TH "ZMQ_RECVMSG" "3" "02/18/2017" "0MQ 4\&.2\&.2" "0MQ Manual"
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.\" -----------------------------------------------------------------
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.\" * Define some portability stuff
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.\" -----------------------------------------------------------------
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.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.\" http://bugs.debian.org/507673
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.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
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.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.ie \n(.g .ds Aq \(aq
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.el .ds Aq '
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.\" -----------------------------------------------------------------
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.\" * set default formatting
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.\" -----------------------------------------------------------------
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.\" disable hyphenation
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.nh
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.\" disable justification (adjust text to left margin only)
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.ad l
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.\" -----------------------------------------------------------------
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.\" * MAIN CONTENT STARTS HERE *
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.\" -----------------------------------------------------------------
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.SH "NAME"
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zmq_recvmsg \- receive a message part from a socket
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.SH "SYNOPSIS"
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.sp
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\fBint zmq_recvmsg (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
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.SH "DESCRIPTION"
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.sp
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The \fIzmq_recvmsg()\fR function shall receive a message part 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 message parts available on the specified \fIsocket\fR the \fIzmq_recvmsg()\fR function shall block until the request can be satisfied\&. The \fIflags\fR argument is a combination of the flags defined below:
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.PP
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\fBZMQ_DONTWAIT\fR
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.RS 4
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Specifies that the operation should be performed in non\-blocking mode\&. If there are no messages available on the specified
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\fIsocket\fR, the
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\fIzmq_recvmsg()\fR
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function shall fail with
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\fIerrno\fR
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set to EAGAIN\&.
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.RE
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.if n \{\
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.sp
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.\}
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.RS 4
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.it 1 an-trap
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.nr an-no-space-flag 1
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.nr an-break-flag 1
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.br
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.ps +1
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\fBNote\fR
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.ps -1
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.br
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.sp
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this API method is deprecated in favor of zmq_msg_recv(3)\&.
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.sp .5v
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.RE
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.SS "Multi\-part messages"
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.sp
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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\&. The total number of message parts is unlimited except by available memory\&.
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.sp
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An application that processes multi\-part messages must use the \fIZMQ_RCVMORE\fR \fBzmq_getsockopt\fR(3) option after calling \fIzmq_recvmsg()\fR to determine if there are further parts to receive\&.
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.SH "RETURN VALUE"
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.sp
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The \fIzmq_recvmsg()\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\&.
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.SH "ERRORS"
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.PP
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\fBEAGAIN\fR
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.RS 4
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Non\-blocking mode was requested and no messages are available at the moment\&.
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.RE
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.PP
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\fBENOTSUP\fR
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.RS 4
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The
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\fIzmq_recvmsg()\fR
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operation is not supported by this socket type\&.
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.RE
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.PP
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\fBEFSM\fR
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.RS 4
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The
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\fIzmq_recvmsg()\fR
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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
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\fImessaging patterns\fR
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section of
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\fBzmq_socket\fR(3)
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for more information\&.
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.RE
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.PP
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\fBETERM\fR
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.RS 4
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The 0MQ
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\fIcontext\fR
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associated with the specified
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\fIsocket\fR
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was terminated\&.
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.RE
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.PP
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\fBENOTSOCK\fR
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.RS 4
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The provided
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\fIsocket\fR
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was invalid\&.
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.RE
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.PP
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\fBEINTR\fR
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.RS 4
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The operation was interrupted by delivery of a signal before a message was available\&.
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.RE
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.PP
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\fBEFAULT\fR
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.RS 4
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The message passed to the function was invalid\&.
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.RE
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.SH "EXAMPLE"
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.PP
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\fBReceiving a message from a socket\fR.
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.sp
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.if n \{\
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.RS 4
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.\}
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.nf
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/* Create an empty 0MQ message */
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zmq_msg_t msg;
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int rc = zmq_msg_init (&msg);
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assert (rc == 0);
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/* Block until a message is available to be received from socket */
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rc = zmq_recvmsg (socket, &msg, 0);
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assert (rc != \-1);
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/* Release message */
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zmq_msg_close (&msg);
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.fi
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.if n \{\
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.RE
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.\}
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.PP
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\fBReceiving a multi-part message\fR.
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.sp
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.if n \{\
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.RS 4
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.\}
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.nf
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int more;
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size_t more_size = sizeof (more);
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do {
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/* Create an empty 0MQ message to hold the message part */
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zmq_msg_t part;
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int rc = zmq_msg_init (&part);
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assert (rc == 0);
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/* Block until a message is available to be received from socket */
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rc = zmq_recvmsg (socket, &part, 0);
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assert (rc != \-1);
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/* Determine if more message parts are to follow */
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rc = zmq_getsockopt (socket, ZMQ_RCVMORE, &more, &more_size);
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assert (rc == 0);
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zmq_msg_close (&part);
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} while (more);
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.fi
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.if n \{\
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.RE
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.\}
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.sp
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.SH "SEE ALSO"
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.sp
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\fBzmq_recv\fR(3) \fBzmq_send\fR(3) \fBzmq_getsockopt\fR(3) \fBzmq_socket\fR(7) \fBzmq\fR(7)
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.SH "AUTHORS"
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.sp
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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[]\&.
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