NAME

       zmq_recvmsg - receive a message part from a socket

SYNOPSIS

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

DESCRIPTION

       The zmq_recvmsg() 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_recvmsg() 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_recvmsg() function shall fail with
           errno set to EAGAIN.

           Note
           this API method is deprecated in favor of zmq_msg_recv(3).

   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_recvmsg() to determine if there are further
       parts to receive.

RETURN VALUE

       The zmq_recvmsg() 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 no messages are available at the moment.

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

       EFSM
           The zmq_recvmsg() 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_recvmsg (socket, &msg, 0);
           assert (rc != -1);
           /* 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_recvmsg (socket, &part, 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_getsockopt(3) zmq_socket(7) zmq(7)

AUTHORS

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       Contribution Policy at http://www.zeromq.org/docs:contributing.