ZMQ_MSG_INIT(3) 0MQ Manual ZMQ_MSG_INIT(3)NAME
zmq_msg_init - initialise empty 0MQ message
SYNOPSIS
int zmq_msg_init (zmq_msg_t *msg);
DESCRIPTION
The zmq_msg_init() function shall initialise the message object referenced by msg to represent an empty message. This function is most
useful when called before receiving a message with zmq_recv().
Caution
Never access zmq_msg_t members directly, instead always use the zmq_msg family of functions.
Caution
The functions zmq_msg_init(), zmq_msg_init_data() and zmq_msg_init_size() are mutually exclusive. Never initialize the same zmq_msg_t
twice.
RETURN VALUE
The zmq_msg_init() function shall return zero if successful. Otherwise it shall return -1 and set errno to one of the values defined below.
ERRORS
No errors are defined.
EXAMPLE
Receiving a message from a socket.
zmq_msg_t msg;
rc = zmq_msg_init (&msg);
assert (rc == 0);
rc = zmq_recv (socket, &msg, 0);
assert (rc == 0);
SEE ALSO zmq_msg_init_size(3)zmq_msg_init_data(3)zmq_msg_close(3)zmq_msg_data(3)zmq_msg_size(3)zmq(7)AUTHORS
This manual page was written by the 0MQ community.
0MQ 2.2.0 04/04/2012 ZMQ_MSG_INIT(3)
Check Out this Related Man Page
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)