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Documentation rewrite
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mato committed Mar 9, 2010
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4 changes: 2 additions & 2 deletions doc/Makefile.am
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Expand Up @@ -4,8 +4,8 @@ MAN3 = zmq_bind.3 zmq_close.3 zmq_connect.3 zmq_flush.3 zmq_init.3 \
zmq_msg_init_data.3 zmq_msg_init_size.3 zmq_msg_move.3 zmq_msg_size.3 \
zmq_poll.3 zmq_recv.3 zmq_send.3 zmq_setsockopt.3 zmq_socket.3 \
zmq_strerror.3 zmq_term.3 zmq_version.3
MAN7 = zmq.7 zmq_tcp.7 zmq_udp.7 zmq_pgm.7 zmq_inproc.7 zmq_ipc.7 \
zmq_cpp.7 zmq_java.7
MAN7 = zmq.7 zmq_tcp.7 zmq_pgm.7 zmq_epgm.7 zmq_inproc.7 zmq_ipc.7 \
zmq_cpp.7
MAN_DOC = $(MAN1) $(MAN3) $(MAN7)

MAN_TXT = $(MAN1:%.1=%.txt)
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8 changes: 8 additions & 0 deletions doc/asciidoc.conf
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@@ -1,3 +1,6 @@
[paradef-default]
literal-style=template="literalparagraph"

[macros]
(?su)[\\]?(?P<name>linkzmq):(?P<target>\S*?)\[(?P<attrlist>.*?)\]=

Expand Down Expand Up @@ -32,3 +35,8 @@ template::[header-declarations]
</refnamediv>
endif::backend-docbook[]
endif::doctype-manpage[]

[replacements]
ifdef::backend-xhtml11[]
0MQ=ØMQ
endif::backend-xhtml11[]
227 changes: 137 additions & 90 deletions doc/zmq.txt
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Expand Up @@ -9,59 +9,69 @@ zmq - 0MQ lightweight messaging kernel

SYNOPSIS
--------
0MQ is an extension of POSIX sockets. It is a library that augments standard
networking sockets by special capabilities that you can otherwise get only
by using specialised "messaging middleware" products, such as automated
handling of connections and disconnections, delivery of a message to multiple
destinations, load balancing messages, sophisticated message filtering etc.
*#include <zmq.h>*

0MQ is designed to be extremely fast. Expected end-to-end latencies for
messages passed over a LAN are in tens of microseconds. Expected
throughputs are to be measured in millions of messages per second.
*cc* ['flags'] 'files' *-lzmq* ['libraries']

0MQ is designed to be very thin. It requires no more than couple of
pages in resident memory and is thus well suited for any environment ranging
from small embedded devices, routers and cell phones to enterprise-scale
data centers.

0MQ runs on a wide range of operating systems and supports variety of processor
microarchitectures.
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.

0MQ is accessible from a large set of programming languages.
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.

0MQ is fully open sourced LGPL-licensed software.


CONTEXT
-------
Each 0MQ socket lives within a specific context. Creating and destroying
context is a counterpart of library initialisation/deinitialisation as used
elsewhere. Ability to create multiple contexts saves the day when an application
happens to link (indirectly and involuntarily) with several instances of 0MQ.
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::
linkzmq:zmq_init[3]

Uninitialise 0MQ context::
Terminate 0MQ context::
linkzmq:zmq_term[3]


MESSAGES
--------
Message is a discrete unit of data passed between applications or components
of the same application. 0MQ message has no internal structure, it is an opaque
BLOB. When writing data to or reading data from the message, you are free to
use any of the many serialisation libraries available. Alternatively, you can
use your own serialisation code. The latter option is especially useful when
migrating legacy applications to 0MQ - there's no need to break existing
message formats.
Thread safety
^^^^^^^^^^^^^
A 0MQ 'context' is thread safe and may be shared among as many application
threads as the application has requested using the _app_threads_ parameter to
_zmq_init()_, without any additional locking required on the part of the
caller. Each 0MQ socket belonging to a particular 'context' may only be used
by *the thread that created it* using _zmq_socket()_.


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 BLOBs.

The following functions are provided to work with messages:

Initialise a message::
linkzmq:zmq_msg_init[3]
linkzmq:zmq_msg_size[3]
linkzmq:zmq_msg_data[3]
linkzmq:zmq_msg_init_size[3]
linkzmq:zmq_msg_init_data[3]

Uninitialise a message::
Release a message::
linkzmq:zmq_msg_close[3]

Access message content::
Expand All @@ -73,10 +83,21 @@ Message manipulation::
linkzmq:zmq_msg_move[3]


SOCKETS
-------
0MQ sockets are very similar to POSIX sockets. See following manual pages to
understand them in depth.
Sockets
~~~~~~~
Standard sockets present a _synchronous_ interface to either connection-mode
reliable byte streams (SOCK_STREAM), or connection-less unreliable datagrams
(SOCK_DGRAM). In comparison, 0MQ sockets present an abstraction of a
asynchronous _message queue_, with the exact queueing semantics depending on
the socket type (_messaging pattern_) in use. See linkzmq:zmq_socket[3] for the
_messaging patterns_ provided.

0MQ sockets being _asynchronous_ means that the timings of the physical
connection setup and teardown, reconnect and effective delivery are organized
by 0MQ itself, and that messages may be _queued_ in the event that a peer is
unavailable to receive them.

The following functions are provided to work with sockets:

Creating a socket::
linkzmq:zmq_socket[3]
Expand All @@ -91,82 +112,108 @@ Establishing a message flow::
linkzmq:zmq_bind[3]
linkzmq:zmq_connect[3]

Sending & receiving messages::
Sending and receiving messages::
linkzmq:zmq_send[3]
linkzmq:zmq_flush[3]
linkzmq:zmq_recv[3]


MULTIPLEXING
------------
0MQ allows you to handle multiple sockets (0MQ as well as standard POSIX)
in an asynchronous manner.

Poll for I/O events::
linkzmq:zmq_poll[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
linkzmq:zmq_poll[3].

ERROR HANDLING
--------------
0MQ defines couple of non-POSIX error codes. Use following functions to handle
them neatly.

Convert error code into human readable string::
linkzmq:zmq_strerror[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.

TRANSPORTS
----------
0MQ allows for using different underlying transport mechanisms (even multiple
at once). Each transport mechanism has its own advantages and drawbacks. For
detailed description of individual mechanisms check following manual pages:
The following transport mechanisms are provided:

TCP/IP transport::
Unicast transport using TCP::
linkzmq:zmq_tcp[7]

UDP reliable multicast transport::
linkzmq:zmq_udp[7]

PGM reliable multicast transport::
Reliable multicast transport using PGM::
linkzmq:zmq_pgm[7]

Inter-process transport::
Local inter-process communication transport::
linkzmq:zmq_ipc[7]

In-process (inter-thread) transport::
Local in-process (inter-thread) communication transport::
linkzmq:zmq_inproc[7]


DEVICES
-------
Aside of the messaging library (a.k.a. messaging kernel) 0MQ provides pre-built
executables - devices - to serve as middle nodes in complex messaging
topologies. For detailed description of individual devices check following
manual pages:
Devices
~~~~~~~
Apart from the 0MQ library the 0MQ distribution includes 'devices' which are
building blocks intended to serve as intermediate nodes in complex messaging
topologies.

Forwarder device for PUB/SUB messaging::
The following devices are provided:

Forwarder device for request-response messaging::
linkzmq:zmq_queue[1]

Forwarder device for publish-subscribe messaging::
linkzmq:zmq_forwarder[1]

Streamer device for UPSTREAM/DOWNSTREAM messaging::
Streamer device for parallelized pipeline messaging::
linkzmq:zmq_streamer[1]

Forwarder device for REQ/REP messaging::
linkzmq:zmq_queue[1]

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.

A _zmq_strerror()_ function is provided to translate 0MQ-specific error codes
into error message strings. For further details refer to
linkzmq:zmq_strerror[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.

LANGUAGES
---------
0MQ manual pages provide info on C API. To find out how the your
favourite language API maps to C API and thus how to find relevant manual pages,
see following articles:

$$C++$$::
linkzmq:zmq_cpp[7]
C++ language binding
~~~~~~~~~~~~~~~~~~~~
The 0MQ distribution includes a $$C++$$ language binding, which is documented
separately in linkzmq:zmq_cpp[7].

Java::
linkzmq:zmq_java[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.

AUTHOR
------
Martin Sustrik <sustrik at 250bpm dot com>

AUTHORS
-------
The 0MQ documentation was written by Martin Sustrik <[email protected]> and
Martin Lucina <[email protected]>.


RESOURCES
---------
Main web site: <http://www.zeromq.org/>

Report bugs to the 0MQ development mailing list: <[email protected]>


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.
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