NAME

       zmq_msg_recv - receive a message part from a socket

SYNOPSIS

       int zmq_msg_recv (zmq_msg_t *msg, void *socket, int flags);

DESCRIPTION

       The zmq_msg_recv() function is identical to zmq_recvmsg(3), which shall be deprecated in
       future versions. zmq_msg_recv() is more consistent with other message manipulation
       functions.

       The zmq_msg_recv() function shall receive a message part from the socket referenced by the
       socket argument and store it in the message referenced by the msg argument. Any content
       previously stored in msg shall be properly deallocated. If there are no message parts
       available on the specified socket the zmq_msg_recv() function shall block until the
       request can be satisfied. The flags argument is a combination of the flags defined below:

       ZMQ_DONTWAIT
           Specifies that the operation should be performed in non-blocking mode. If there are no
           messages available on the specified socket, the zmq_msg_recv() function shall fail
           with errno set to EAGAIN.

   Multi-part messages
       A 0MQ message is composed of 1 or more message parts. Each message part is an independent
       zmq_msg_t in its own right. 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 processes multi-part messages must use the ZMQ_RCVMORE
       zmq_getsockopt(3) option after calling zmq_msg_recv() to determine if there are further
       parts to receive.

RETURN VALUE

       The zmq_msg_recv() 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
           Either the timeout set via the socket-option ZMQ_RCVTIMEO (see zmq_setsockopt(3)) has
           been reached (flag ZMQ_DONTWAIT not set) without being able to read a message from the
           socket or there are no messages available at the moment (flag ZMQ_DONTWAIT set) and
           the operation would block.

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

       EFSM
           The zmq_msg_recv() 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 a message was available.

       EFAULT
           The message passed to the function was invalid.

EXAMPLE

       Receiving a message from a socket.

           /* Create an empty 0MQ message */
           zmq_msg_t msg;
           int rc = zmq_msg_init (&msg);
           assert (rc == 0);
           /* Block until a message is available to be received from socket */
           rc = zmq_msg_recv (&msg, socket, 0);
           assert (rc != -1);
           /* Release message */
           zmq_msg_close (&msg);

       Receiving a multi-part message.

           int more;
           size_t more_size = sizeof (more);
           do {
               /* Create an empty 0MQ message to hold the message part */
               zmq_msg_t part;
               int rc = zmq_msg_init (&part);
               assert (rc == 0);
               /* Block until a message is available to be received from socket */
               rc = zmq_msg_recv (&part, socket, 0);
               assert (rc != -1);
               /* Determine if more message parts are to follow */
               rc = zmq_getsockopt (socket, ZMQ_RCVMORE, &more, &more_size);
               assert (rc == 0);
               zmq_msg_close (&part);
           } while (more);

SEE ALSO

       zmq_recv(3) zmq_send(3) zmq_msg_send(3) zmq_getsockopt(3) zmq_setsockopt(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.