NAME

       zmq_recv - receive a message part from a socket

SYNOPSIS

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

DESCRIPTION

       The zmq_recv() function shall receive a message from the socket referenced by the socket argument and
       store it in the buffer referenced by the buf argument. Any bytes exceeding the length specified by the
       len argument shall be truncated. 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: The buf argument may be null if len is zero.

       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_recv() function shall fail with errno set to EAGAIN.

   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 processes multi-part messages must use the ZMQ_RCVMORE zmq_getsockopt(3) option after
       calling zmq_recv() to determine if there are further parts to receive.

RETURN VALUE

       The zmq_recv() function shall return number of bytes in the message if successful. Note that the value
       can exceed the value of the len parameter in case the message was truncated. If not successful the
       function 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.

EXAMPLE

       Receiving a message from a socket.

           char buf [256];
           nbytes = zmq_recv (socket, buf, 256, 0);
           assert (nbytes != -1);

SEE ALSO

       zmq_send(3) zmq_getsockopt(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.

0MQ 4.3.2                                          04/21/2020                                        ZMQ_RECV(3)