NAME

       zmq_send_const - send a constant-memory message part on a socket

SYNOPSIS

       int zmq_send_const (void *socket, void *buf, size_t len, int flags);

DESCRIPTION

       The zmq_send_const() function shall queue a message created from the buffer referenced by
       the buf and len arguments. The message buffer is assumed to be constant-memory and will
       therefore not be copied or deallocated in any way. The flags argument is a combination of
       the flags defined below:

       ZMQ_DONTWAIT
           For socket types (DEALER, PUSH) that block when there are no available peers (or all
           peers have full high-water mark), specifies that the operation should be performed in
           non-blocking mode. If the message cannot be queued on the socket, the zmq_send_const()
           function shall fail with errno set to EAGAIN.

       ZMQ_SNDMORE
           Specifies that the message being sent is a multi-part message, and that further
           message parts are to follow. Refer to the section regarding multi-part messages below
           for a detailed description.

           Note
           A successful invocation of zmq_send_const() does not indicate that the message has
           been transmitted to the network, only that it has been queued on the socket and 0MQ
           has assumed responsibility for the message.

   Multi-part messages
       A 0MQ message is composed of 1 or more message parts. 0MQ ensures atomic delivery of
       messages: peers shall receive either all message parts of a message or none at all. The
       total number of message parts is unlimited except by available memory.

       An application that sends multi-part messages must use the ZMQ_SNDMORE flag when sending
       each message part except the final one.

RETURN VALUE

       The zmq_send_const() function shall return number of bytes in the message if successful.
       Otherwise it shall return -1 and set errno to one of the values defined below.

ERRORS

       EAGAIN
           Non-blocking mode was requested and the message cannot be sent at the moment.

       ENOTSUP
           The zmq_send_const() operation is not supported by this socket type.

       EFSM
           The zmq_send_const() 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 messaging patterns
           section of zmq_socket(3) for more information.

       ETERM
           The 0MQ context associated with the specified socket was terminated.

       ENOTSOCK
           The provided socket was invalid.

       EINTR
           The operation was interrupted by delivery of a signal before the message was sent.

       EHOSTUNREACH
           The message cannot be routed.

EXAMPLE

       Sending a multi-part message.

           /* Send a multi-part message consisting of three parts to socket */
           rc = zmq_send_const (socket, "ABC", 3, ZMQ_SNDMORE);
           assert (rc == 3);
           rc = zmq_send_const (socket, "DEFGH", 5, ZMQ_SNDMORE);
           assert (rc == 5);
           /* Final part; no more parts to follow */
           rc = zmq_send_const (socket, "JK", 2, 0);
           assert (rc == 2);

SEE ALSO

       zmq_send(3) zmq_recv(3) zmq_socket(7) zmq(7)

AUTHORS

       This page was written by the 0MQ community. To make a change please read the 0MQ
       Contribution Policy at http://www.zeromq.org/docs:contributing.