ZMQ_RECVMSG(3) 0MQ Manual ZMQ_RECVMSG(3)NAMEzmq_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.
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_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 ALSOzmq_recv(3)zmq_send(3)zmq_getsockopt(3)zmq_socket(7)zmq(7)AUTHORS
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0MQ 4.1.0 08/17/2015 ZMQ_RECVMSG(3)
