Autobahn|Python

WebSocket & WAMP for Python on Twisted and asyncio.

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Quick Links: Source Code - Documentation - WebSocket Examples - WAMP Examples

Community: Mailing list - StackOverflow - Twitter - IRC #autobahn/chat.freenode.net

Companion Projects: Autobahn|JS - Autobahn|Cpp - Autobahn|Testsuite - Crossbar.io - WAMP

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 2 and 3, 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
• compatible with Python 2.7 and 3.4 or later (including 3.7)
• runs on CPython, PyPy and Jython
• 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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Native vector extensions (NVX)

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

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

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.

To use cbor2, an alternative, highly flexible and standards complicant CBOR implementation, set the environment variable:

AUTOBAHN_USE_CBOR2=1

Note

cbor2 is not used by default, because it is significantly slower currently in our benchmarking for WAMP message serialization on both CPython and PyPy compared to cbor.

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.