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96 lines
3.3 KiB
Plaintext
96 lines
3.3 KiB
Plaintext
= zmq_send_const(3)
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== NAME
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zmq_send_const - send a constant-memory message part on a socket
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== SYNOPSIS
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*int zmq_send_const (void '*socket', const void '*buf', size_t 'len', int 'flags');*
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== DESCRIPTION
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The _zmq_send_const()_ function shall queue a message created from the buffer
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referenced by the 'buf' and 'len' arguments. The message buffer is assumed
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to be constant-memory and will therefore not be copied or deallocated
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in any way. The '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_send_const()_ 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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NOTE: A successful invocation of _zmq_send_const()_ 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.
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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. 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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The _zmq_send_const()_ function shall return number of bytes in the message
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if successful. 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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*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_send_const()_ operation is not supported by this socket type.
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*EFSM*::
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The _zmq_send_const()_ 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 xref:zmq_socket.adoc[zmq_socket] 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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*EHOSTUNREACH*::
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The message cannot be routed.
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== EXAMPLE
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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_send_const (socket, "ABC", 3, ZMQ_SNDMORE);
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assert (rc == 3);
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rc = zmq_send_const (socket, "DEFGH", 5, ZMQ_SNDMORE);
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assert (rc == 5);
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/* Final part; no more parts to follow */
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rc = zmq_send_const (socket, "JK", 2, 0);
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assert (rc == 2);
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----
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== SEE ALSO
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* xref:zmq_send.adoc[zmq_send]
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* xref:zmq_recv.adoc[zmq_recv]
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* xref:zmq_socket.adoc[zmq_socket]
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* xref:zmq.adoc[zmq]
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== AUTHORS
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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 <https://zeromq.org/how-to-contribute/>.
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