zmq_send(3)

SYNOPSIS

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

DESCRIPTION

The zmq_send() function shall queue the message referenced by the msg +argument to be sent to the socket referenced by the socket argument. 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 the +message cannot be queued on the socket, the zmq_send() function shall fail +with errno set to EAGAIN. +
+
+ZMQ_SNDMORE +: +
+Specifies that the message being sent is a multi-part message, and that further +message parts are to follow. Refer to the section regarding multi-part messages +below for a detailed description. +
+

+ + + +

Note

A successful invocation of zmq_send() does not indicate that the +message has been transmitted to the network, only that it has been queued on +the socket and ØMQ has assumed responsibility for the message.

Multi-part messages

A ØMQ message is composed of 1 or more message parts; each message part is an +independent zmq_msg_t in its own right. ØMQ 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 send a multi-part message does so by specifying the +ZMQ_SNDMORE flag to zmq_send(). The presence of this flag indicates to ØMQ +that the message being sent is a multi-part message and that more message parts +are to follow. When the application wishes to send the final message part it +does so by calling zmq_send() without the ZMQ_SNDMORE flag; this indicates +that no more message parts are to follow.

RETURN VALUE

The zmq_send() 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 the message cannot be sent at the moment. +
+
+ENOTSUP +: +
+The zmq_send() operation is not supported by this socket type. +
+
+EFSM +: +
+The zmq_send() 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 ØMQ context associated with the specified socket was terminated. +
+
+EFAULT +: +
+The provided socket was not valid (NULL). +
+
+EINTR +: +
+The operation was interrupted by delivery of a signal before the message was +sent. +
+

EXAMPLE

Filling in a message and sending it to a socket

/* Create a new message, allocating 6 bytes for message content */
+zmq_msg_t msg;
+int rc = zmq_msg_init_size (&msg, 6);
+assert (rc == 0);
+/* Fill in message content with 'AAAAAA' */
+memset (zmq_msg_data (&msg), 'A', 6);
+/* Send the message to the socket */
+rc = zmq_send (socket, &msg, 0);
+assert (rc == 0);

Sending a multi-part message

/* Send a multi-part message consisting of three parts to socket */
+rc = zmq_send (socket, &part1, ZMQ_SNDMORE);
+rc = zmq_send (socket, &part2, ZMQ_SNDMORE);
+/* Final part; no more parts to follow */
+rc = zmq_send (socket, &part3, 0);

AUTHORS

This ØMQ manual page was written by Martin Sustrik <sustrik@250bpm.com> and +Martin Lucina <mato@kotelna.sk>.

+zmq_send(3) Manual Page +

NAME