Autobahn|Python

WebSocket & WAMP for Python on Twisted and asyncio.

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| Quick Links: Source Code <https://github.com/crossbario/autobahn-python>__ - Documentation <https://autobahn.readthedocs.io/en/latest/>__ - WebSocket Examples <https://autobahn.readthedocs.io/en/latest/websocket/examples.html>__ - WAMP Examples <https://autobahn.readthedocs.io/en/latest/wamp/examples.html>__ | Community: Forum <https://crossbar.discourse.group/>__ - StackOverflow <https://stackoverflow.com/questions/tagged/autobahn>__ - Twitter <https://twitter.com/autobahnws>__ - IRC #autobahn/chat.freenode.net <https://webchat.freenode.net/>__ | Companion Projects: Autobahn|JS <https://github.com/crossbario/autobahn-js/>__ - Autobahn|Cpp <https://github.com/crossbario/autobahn-cpp>__ - Autobahn|Testsuite <https://github.com/crossbario/autobahn-testsuite>__ - Crossbar.io <https://crossbar.io>__ - WAMP <https://wamp-proto.org>__

Introduction

Autobahn|Python is a subproject of Autobahn <https://crossbar.io/autobahn>__ and provides open-source implementations of

• The WebSocket Protocol <https://tools.ietf.org/html/rfc6455>__
• The Web Application Messaging Protocol (WAMP) <https://wamp-proto.org/>__

for Python 3.7+ and running on Twisted <https://twistedmatrix.com/>__ and asyncio <https://docs.python.org/3/library/asyncio.html>__.

You can use Autobahn|Python to create clients and servers in Python speaking just plain WebSocket or WAMP.

WebSocket allows bidirectional real-time messaging on the Web <https://crossbario.com/blog/post/websocket-why-what-can-i-use-it/>__ and beyond, while WAMP <https://wamp-proto.org/>__ adds real-time application communication on top of WebSocket.

WAMP provides asynchronous Remote Procedure Calls and Publish & Subscribe for applications in one protocol running over WebSocket <https://tools.ietf.org/html/rfc6455>. WAMP is a routed protocol, so you need a WAMP Router to connect your Autobahn|Python based clients. We provide Crossbar.io <https://crossbar.io>, but there are other options <https://wamp-proto.org/implementations.html#routers>__ as well.

.. note::

**Autobahn\|Python** up to version v19.11.2 supported Python 2 and 3.4+,
and up to version v20.7.1 supported Python 3.5+,
and up to version v21.2.1 supported Python 3.6+.

Features

• framework for WebSocket <https://tools.ietf.org/html/rfc6455>__ and WAMP <https://wamp-proto.org/>__ clients and servers
• runs on CPython <https://python.org/>__ and PyPy <https://pypy.org/>
• runs under Twisted <https://twistedmatrix.com/>__ and asyncio <https://docs.python.org/3/library/asyncio.html>__ - implements WebSocket RFC6455 <https://tools.ietf.org/html/rfc6455>__ and Draft Hybi-10+
• implements WebSocket compression <https://tools.ietf.org/html/draft-ietf-hybi-permessage-compression>__
• implements WAMP <https://wamp-proto.org/>__, the Web Application Messaging Protocol
• high-performance, fully asynchronous implementation
• best-in-class standards conformance (100% strict passes with Autobahn Testsuite <https://crossbar.io/autobahn#testsuite>: Client <https://autobahn.ws/testsuite/reports/clients/index.html> Server <https://autobahn.ws/testsuite/reports/servers/index.html>__)
• message-, frame- and streaming-APIs for WebSocket
• supports TLS (secure WebSocket) and proxies
• Open-source (MIT license <https://github.com/crossbario/autobahn-python/blob/master/LICENSE>__)

Show me some code

To give you a first impression, here are two examples. We have lot more in the repo <https://github.com/crossbario/autobahn-python/tree/master/examples>__.

WebSocket Echo Server

Here is a simple WebSocket Echo Server that will echo back any WebSocket
message received:

.. code:: python

    from autobahn.twisted.websocket import WebSocketServerProtocol
    # or: from autobahn.asyncio.websocket import WebSocketServerProtocol

    class MyServerProtocol(WebSocketServerProtocol):

        def onConnect(self, request):
            print("Client connecting: {}".format(request.peer))

        def onOpen(self):
            print("WebSocket connection open.")

        def onMessage(self, payload, isBinary):
            if isBinary:
                print("Binary message received: {} bytes".format(len(payload)))
            else:
                print("Text message received: {}".format(payload.decode('utf8')))

            # echo back message verbatim
            self.sendMessage(payload, isBinary)

        def onClose(self, wasClean, code, reason):
            print("WebSocket connection closed: {}".format(reason))

To actually run above server protocol, you need some lines of `boilerplate <https://autobahn.readthedocs.io/en/latest/websocket/programming.html#running-a-server>`__.

WAMP Application Component

Here is a WAMP Application Component that performs all four types of actions that WAMP provides:

#. subscribe to a topic #. publish an event #. register a procedure #. call a procedure

.. code:: python

from autobahn.twisted.wamp import ApplicationSession
# or: from autobahn.asyncio.wamp import ApplicationSession

class MyComponent(ApplicationSession):

    @inlineCallbacks
    def onJoin(self, details):

        # 1. subscribe to a topic so we receive events
        def onevent(msg):
            print("Got event: {}".format(msg))

        yield self.subscribe(onevent, 'com.myapp.hello')

        # 2. publish an event to a topic
        self.publish('com.myapp.hello', 'Hello, world!')

        # 3. register a procedure for remote calling
        def add2(x, y):
            return x + y

        self.register(add2, 'com.myapp.add2')

        # 4. call a remote procedure
        res = yield self.call('com.myapp.add2', 2, 3)
        print("Got result: {}".format(res))

Above code will work on Twisted and asyncio by changing a single line (the base class of MyComponent). To actually run above application component, you need some lines of boilerplate <https://autobahn.readthedocs.io/en/latest/wamp/programming.html#running-components>__ and a WAMP Router <https://autobahn.readthedocs.io/en/latest/wamp/programming.html#running-a-wamp-router>__.

Extensions

Networking framework

Autobahn runs on both Twisted and asyncio. To select the respective netoworking framework, install flavor:

* ``asyncio``: Install asyncio (when on Python 2, otherwise it's included in the standard library already) and asyncio support in Autobahn
* ``twisted``: Install Twisted and Twisted support in Autobahn

-----


WebSocket acceleration and compression

• accelerate: Install WebSocket acceleration - Only use on CPython - not on PyPy (which is faster natively)
• compress: Install (non-standard) WebSocket compressors bzip2 and snappy (standard deflate based WebSocket compression is already included in the base install)

Encryption and WAMP authentication

Autobahn supports running over TLS (for WebSocket and all WAMP transports) as well as **WAMP-cryposign** authentication.

To install use this flavor:

* ``encryption``: Installs TLS and WAMP-cryptosign dependencies

Autobahn also supports **WAMP-SCRAM** authentication. To install:

* ``scram``: Installs WAMP-SCRAM dependencies

-----


XBR
~~~

Autobahn includes support for `XBR <https://xbr.network/>`__. To install use this flavor:

* ``xbr``:

To install:

.. code:: console

    pip install autobahn[xbr]

or (Twisted, with more bells an whistles)

.. code:: console

    pip install autobahn[twisted,encryption,serialization,xbr]

or (asyncio, with more bells an whistles)

.. code:: console

    pip install autobahn[asyncio,encryption,serialization,xbr]

-----


Native vector extensions (NVX)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

> This is NOT yet complete - ALPHA!

Autobahn contains **NVX**, a network accelerator library that provides SIMD accelerated native vector code for WebSocket (XOR masking) and UTF-8 validation.

.. note:

    NVX lives in namespace `autobahn.nvx` and currently requires a x86-86 CPU with at least SSE2 and makes use of SSE4.1 if available. The code is written using vector instrinsics, should compile with both GCC and Clang,and interfaces with Python using CFFI, and hence runs fast on PyPy.

-----


WAMP Serializers
~~~~~~~~~~~~~~~~

* ``serialization``: To install additional WAMP serializers: CBOR, MessagePack, UBJSON and Flatbuffers

**Above is for advanced uses. In general we recommend to use CBOR where you can,
and JSON (from the standard library) otherwise.**

-----

To install Autobahn with all available serializers:

.. code:: console

    pip install autobahn[serializers]

or (development install)

.. code:: console

    pip install -e .[serializers]

Further, to speed up JSON on CPython using ``ujson``, set the environment variable:

.. code:: console

    AUTOBAHN_USE_UJSON=1

.. warning::

    Using ``ujson`` (on both CPython and PyPy) will break the ability of Autobahn
    to transport and translate binary application payloads in WAMP transparently.
    This ability depends on features of the regular JSON standard library module
    not available on ``ujson``.


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