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ZMQ_RECV(3)                       0MQ Manual                       ZMQ_RECV(3)

NAME
       zmq_recv - receive a message from a socket

SYNOPSIS
       int zmq_recv (void *socket, zmq_msg_t *msg, int flags);

DESCRIPTION
       The zmq_recv() function shall receive a message 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 messages available on
       the specified socket the zmq_recv() function shall block until the
       request can be satisfied. The flags argument is a combination of the
       flags defined below:

       ZMQ_NOBLOCK
           Specifies that the operation should be performed in non-blocking
           mode. If there are no messages available on the specified socket,
           the zmq_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.

       An application wishing to determine if a message is composed of
       multiple parts does so by retrieving the value of the ZMQ_RCVMORE
       socket option on the socket it is receiving the message from. If there
       are no message parts to follow, or if the message is not composed of
       multiple parts, ZMQ_RCVMORE shall report a value of zero. Otherwise,
       ZMQ_RCVMORE shall report a value of 1, indicating that more message
       parts are to follow.

RETURN VALUE
       The zmq_recv() function shall return zero 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 no messages are available at
           the moment.

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

       EFSM
           The zmq_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_recv (socket, &msg, 0);
           assert (rc == 0);
           /* Release message */
           zmq_msg_close (&msg);

       Receiving a multi-part message.

           int64_t 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_recv (socket, &part, 0);
               assert (rc == 0);
               /* 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_send(3) zmq_getsockopt(3) zmq_socket(7) zmq(7)

AUTHORS
       This manual page was written by the 0MQ community.

0MQ 2.2.0                         04/04/2012                       ZMQ_RECV(3)