ZMQ_RECV(3) 0MQ Manual ZMQ_RECV(3)
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
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_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_setsockopt(3) zmq_socket(7) zmq(7)
AUTHORS
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0MQ 4.3.4 01/18/2023 ZMQ_RECV(3)
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