Autobahn|Python

WebSocket & WAMP for Python on Twisted and asyncio.

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Introduction

Autobahn|Python is a subproject of Autobahn and provides open-source implementations of

• The WebSocket Protocol
• The Web Application Messaging Protocol (WAMP)

for Python 3.7+ and running on Twisted and asyncio.

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 and beyond, while WAMP 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. WAMP is a routed protocol, so you need a WAMP Router to connect your Autobahn|Python based clients. We provide Crossbar.io, but there are other options as well.

Features

• framework for WebSocket and WAMP clients and servers
• runs on CPython and PyPy <https://pypy.org/>
• runs under Twisted and asyncio - implements WebSocket RFC6455 and Draft Hybi-10+
• implements WebSocket compression
• implements WAMP, the Web Application Messaging Protocol
• high-performance, fully asynchronous implementation
• best-in-class standards conformance (100% strict passes with Autobahn Testsuite: Client Server)
• message-, frame- and streaming-APIs for WebSocket
• supports TLS (secure WebSocket) and proxies
• Open-source (MIT license)

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Show me some code

To give you a first impression, here are two examples. We have lot more in the repo.

WebSocket Echo Server

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

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.

WAMP Application Component

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

1. subscribe to a topic
2. publish an event
3. register a procedure
4. call a procedure

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 and 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

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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)

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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

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XBR

Autobahn includes support for XBR. To install use this flavor:

• xbr:

To install:

pip install autobahn[xbr]

or (Twisted, with more bells an whistles)

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

or (asyncio, with more bells an whistles)

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

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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.

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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.

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To install Autobahn with all available serializers:

pip install autobahn[serializers]

or (development install)

pip install -e .[serializers]

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

AUTOBAHN_USE_UJSON=1