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120 lines
3.5 KiB
Plaintext
120 lines
3.5 KiB
Plaintext
zmq_recv(3)
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===========
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NAME
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----
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zmq_recv - receive a message from a socket
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SYNOPSIS
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--------
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*int zmq_recv (void '*socket', zmq_msg_t '*msg', int 'flags');*
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DESCRIPTION
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-----------
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The _zmq_recv()_ function shall receive a message from the socket referenced by
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the 'socket' argument and store it in the message referenced by the 'msg'
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argument. Any content previously stored in 'msg' shall be properly deallocated.
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If there are no messages available on the specified 'socket' the _zmq_recv()_
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function shall block until the request can be satisfied. The 'flags' argument
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is a combination of the flags defined below:
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*ZMQ_DONTWAIT*::
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Specifies that the operation should be performed in non-blocking mode. If there
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are no messages available on the specified 'socket', the _zmq_recv()_ function
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shall fail with 'errno' set to EAGAIN.
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Multi-part messages
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~~~~~~~~~~~~~~~~~~~
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A 0MQ message is composed of 1 or more message parts; each message part is an
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independent 'zmq_msg_t' in its own right. 0MQ ensures atomic delivery of
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messages; peers shall receive either all _message parts_ of a message or none
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at all.
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The total number of message parts is unlimited.
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An application wishing to determine if a message is composed of multiple parts
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does so by retrieving the value of the _ZMQ_RCVMORE_ socket option on the
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'socket' it is receiving the message from. If there are no message parts to
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follow, or if the message is not composed of multiple parts, _ZMQ_RCVMORE_
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shall report a value of zero. Otherwise, _ZMQ_RCVMORE_ shall report a value of
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1, indicating that more message parts are to follow.
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RETURN VALUE
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------------
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The _zmq_recv()_ function shall return zero if successful. Otherwise it shall
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return `-1` and set 'errno' to one of the values defined below.
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ERRORS
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------
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*EAGAIN*::
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Non-blocking mode was requested and no messages are available at the moment.
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*ENOTSUP*::
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The _zmq_recv()_ operation is not supported by this socket type.
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*EFSM*::
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The _zmq_recv()_ operation cannot be performed on this socket at the moment due
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to the socket not being in the appropriate state. This error may occur with
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socket types that switch between several states, such as ZMQ_REP. See the
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_messaging patterns_ section of linkzmq:zmq_socket[3] for more information.
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*ETERM*::
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The 0MQ 'context' associated with the specified 'socket' was terminated.
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*ENOTSOCK*::
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The provided 'socket' was invalid.
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*EINTR*::
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The operation was interrupted by delivery of a signal before a message was
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available.
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EXAMPLE
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-------
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.Receiving a message from a socket
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----
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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_recv (socket, &msg, 0);
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assert (rc == 0);
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/* Release message */
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zmq_msg_close (&msg);
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----
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.Receiving a multi-part message
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----
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int64_t 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_recv (socket, &part, 0);
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assert (rc == 0);
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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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----
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SEE ALSO
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--------
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linkzmq:zmq_send[3]
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linkzmq:zmq_getsockopt[3]
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linkzmq:zmq_socket[7]
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linkzmq:zmq[7]
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AUTHORS
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-------
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The 0MQ documentation was written by Martin Sustrik <sustrik@250bpm.com> and
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Martin Lucina <mato@kotelna.sk>.
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