zmq_send(3) [debian man page]
ZMQ_SEND(3) 0MQ Manual ZMQ_SEND(3) NAME
zmq_send - send a message on a socket 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. The zmq_msg_t structure passed to zmq_send() is nullified during the call. If you want to send the same message to multiple sockets you have to copy it using (e.g. using zmq_msg_copy()). 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 0MQ has assumed responsibility for the message. 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 send a multi-part message does so by specifying the ZMQ_SNDMORE flag to zmq_send(). The presence of this flag indicates to 0MQ 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 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 the message was sent. EFAULT Invalid message. 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); SEE ALSO
zmq_recv(3) zmq_socket(7) zmq(7) AUTHORS
This manual page was written by the 0MQ community. 0MQ 2.2.0 04/04/2012 ZMQ_SEND(3)
Check Out this Related Man Page
ZMQ(7) 0MQ Manual ZMQ(7) NAME
zmq - 0MQ lightweight messaging kernel SYNOPSIS
#include <zmq.h> cc [flags] files -lzmq [libraries] DESCRIPTION
The 0MQ lightweight messaging kernel is a library which extends the standard socket interfaces with features traditionally provided by specialised messaging middleware products. 0MQ sockets provide an abstraction of asynchronous message queues, multiple messaging patterns, message filtering (subscriptions), seamless access to multiple transport protocols and more. This documentation presents an overview of 0MQ concepts, describes how 0MQ abstracts standard sockets and provides a reference manual for the functions provided by the 0MQ library. Context Before using any 0MQ library functions the caller must initialise a 0MQ context using zmq_init(). The following functions are provided to handle initialisation and termination of a context: Initialise 0MQ context zmq_init(3) Terminate 0MQ context zmq_term(3) Thread safety A 0MQ context is thread safe and may be shared among as many application threads as necessary, without any additional locking required on the part of the caller. Individual 0MQ sockets are not thread safe except in the case where full memory barriers are issued when migrating a socket from one thread to another. In practice this means applications can create a socket in one thread with zmq_socket() and then pass it to a newly created thread as part of thread initialization, for example via a structure passed as an argument to pthread_create(). Multiple contexts Multiple contexts may coexist within a single application. Thus, an application can use 0MQ directly and at the same time make use of any number of additional libraries or components which themselves make use of 0MQ as long as the above guidelines regarding thread safety are adhered to. Messages A 0MQ message is a discrete unit of data passed between applications or components of the same application. 0MQ messages have no internal structure and from the point of view of 0MQ itself they are considered to be opaque binary data. The following functions are provided to work with messages: Initialise a message zmq_msg_init(3) zmq_msg_init_size(3) zmq_msg_init_data(3) Release a message zmq_msg_close(3) Access message content zmq_msg_data(3) zmq_msg_size(3) Message manipulation zmq_msg_copy(3) zmq_msg_move(3) Sockets 0MQ sockets present an abstraction of a asynchronous message queue, with the exact queueing semantics depending on the socket type in use. See zmq_socket(3) for the socket types provided. The following functions are provided to work with sockets: Creating a socket zmq_socket(3) Closing a socket zmq_close(3) Manipulating socket options zmq_getsockopt(3) zmq_setsockopt(3) Establishing a message flow zmq_bind(3) zmq_connect(3) Sending and receiving messages zmq_send(3) zmq_recv(3) Input/output multiplexing. 0MQ provides a mechanism for applications to multiplex input/output events over a set containing both 0MQ sockets and standard sockets. This mechanism mirrors the standard poll() system call, and is described in detail in zmq_poll(3). Transports A 0MQ socket can use multiple different underlying transport mechanisms. Each transport mechanism is suited to a particular purpose and has its own advantages and drawbacks. The following transport mechanisms are provided: Unicast transport using TCP zmq_tcp(7) Reliable multicast transport using PGM zmq_pgm(7) Local inter-process communication transport zmq_ipc(7) Local in-process (inter-thread) communication transport zmq_inproc(7) Devices 0MQ provides devices, which are building blocks that act as intermediate nodes in complex messaging topologies. Devices can act as brokers that other nodes connect to, proxies that connect through to other nodes, or any mix of these two models. You can start a device in an application thread, see zmq_device(3). ERROR HANDLING
The 0MQ library functions handle errors using the standard conventions found on POSIX systems. Generally, this means that upon failure a 0MQ library function shall return either a NULL value (if returning a pointer) or a negative value (if returning an integer), and the actual error code shall be stored in the errno variable. On non-POSIX systems some users may experience issues with retrieving the correct value of the errno variable. The zmq_errno() function is provided to assist in these cases; for details refer to zmq_errno(3). The zmq_strerror() function is provided to translate 0MQ-specific error codes into error message strings; for details refer to zmq_strerror(3). MISCELLANEOUS
The following miscellaneous functions are provided: Report 0MQ library version zmq_version(3) LANGUAGE BINDINGS
The 0MQ library provides interfaces suitable for calling from programs in any language; this documentation documents those interfaces as they would be used by C programmers. The intent is that programmers using 0MQ from other languages shall refer to this documentation alongside any documentation provided by the vendor of their language binding. C++ language binding The 0MQ distribution includes a C++ language binding, which is documented separately in zmq_cpp(7). Other language bindings Other language bindings (Python, Ruby, Java and more) are provided by members of the 0MQ community and pointers can be found on the 0MQ website. AUTHORS
This manual page was written by the 0MQ community. RESOURCES
Main web site: http://www.zeromq.org/ Report bugs to the 0MQ development mailing list: <zeromq-dev@lists.zeromq.org[1]> COPYING
Free use of this software is granted under the terms of the GNU Lesser General Public License (LGPL). For details see the files COPYING and COPYING.LESSER included with the 0MQ distribution. NOTES
1. zeromq-dev@lists.zeromq.org mailto:zeromq-dev@lists.zeromq.org 0MQ 2.2.0 04/04/2012 ZMQ(7)