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133 lines
4.4 KiB
Plaintext
133 lines
4.4 KiB
Plaintext
zmq_msg_send(3)
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===============
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NAME
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----
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zmq_msg_send - send a message part on a socket
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SYNOPSIS
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--------
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*int zmq_msg_send (zmq_msg_t '*msg', void '*socket', int 'flags');*
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DESCRIPTION
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-----------
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The _zmq_msg_send()_ function is identical to linkzmq:zmq_sendmsg[3], which
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shall be deprecated in future versions. _zmq_msg_send()_ is more consistent
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with other message manipulation functions.
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The _zmq_msg_send()_ function shall queue the message referenced by the 'msg'
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argument to be sent to the socket referenced by the 'socket' argument. The
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'flags' argument is a combination of the flags defined below:
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*ZMQ_DONTWAIT*::
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For socket types (DEALER, PUSH) that block (either with ZMQ_IMMEDIATE option set
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and no peer available, or all peers having full high-water mark), specifies that
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the operation should be performed in non-blocking mode. If the message cannot be
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queued on the 'socket', the _zmq_msg_send()_ function shall fail with 'errno' set
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to EAGAIN.
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*ZMQ_SNDMORE*::
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Specifies that the message being sent is a multi-part message, and that further
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message parts are to follow. Refer to the section regarding multi-part messages
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below for a detailed description.
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The _zmq_msg_t_ structure passed to _zmq_msg_send()_ is nullified on a
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successful call. If you want to send the same message to multiple sockets you
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have to copy it (e.g. using _zmq_msg_copy()_). If the call fails, the
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_zmq_msg_t_ structure stays intact, and must be consumed by another call to
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_zmq_msg_send()_ on the same or another socket, or released using
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_zmq_msg_close()_ to avoid a memory leak.
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NOTE: A successful invocation of _zmq_msg_send()_ does not indicate that the
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message has been transmitted to the network, only that it has been queued on
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the 'socket' and 0MQ has assumed responsibility for the message. You do not need
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to call _zmq_msg_close()_ after a successful _zmq_msg_send()_.
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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
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part is an independent 'zmq_msg_t' in its own right. 0MQ ensures atomic
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delivery of messages: peers shall receive either all _message parts_ of a
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message or none at all. The total number of message parts is unlimited except
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by available memory.
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An application that sends multi-part messages must use the _ZMQ_SNDMORE_ flag
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when sending each message part except the final one.
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RETURN VALUE
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------------
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The _zmq_msg_send()_ function shall return number of bytes in the message
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if successful (if number of bytes is higher than 'MAX_INT', the function will
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return 'MAX_INT'). Otherwise it shall return `-1` and set 'errno' to one of the
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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 the message cannot be sent at the moment.
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*ENOTSUP*::
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The _zmq_msg_send()_ operation is not supported by this socket type.
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*EINVAL*::
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The sender tried to send multipart data, which the socket type does not allow.
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*EFSM*::
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The _zmq_msg_send()_ operation cannot be performed on this socket at the moment
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due 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 the message was
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sent.
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*EFAULT*::
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Invalid message.
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*EHOSTUNREACH*::
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The message cannot be routed.
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EXAMPLE
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-------
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.Filling in a message and sending it to a socket
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----
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/* Create a new message, allocating 6 bytes for message content */
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zmq_msg_t msg;
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int rc = zmq_msg_init_size (&msg, 6);
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assert (rc == 0);
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/* Fill in message content with 'AAAAAA' */
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memset (zmq_msg_data (&msg), 'A', 6);
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/* Send the message to the socket */
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rc = zmq_msg_send (&msg, socket, 0);
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assert (rc == 6);
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----
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.Sending a multi-part message
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----
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/* Send a multi-part message consisting of three parts to socket */
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rc = zmq_msg_send (&part1, socket, ZMQ_SNDMORE);
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rc = zmq_msg_send (&part2, socket, ZMQ_SNDMORE);
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/* Final part; no more parts to follow */
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rc = zmq_msg_send (&part3, socket, 0);
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----
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SEE ALSO
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--------
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linkzmq:zmq_recv[3]
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linkzmq:zmq_send[3]
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linkzmq:zmq_msg_recv[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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This page was written by the 0MQ community. To make a change please
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read the 0MQ Contribution Policy at <http://www.zeromq.org/docs:contributing>.
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