Sans-IO WebSocket protocol implementation
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pgjones Switch from bytes_to_send to send returning bytes
This allows the outgoing_data buffer to be removed and instead left to
the user to be concerned/deal with. This makes it very clear when
wsproto has bytes to send (when ``send`` is called), and hence further
clarifies the API. It also matches h11 expectations.
Latest commit fa70960 Jan 13, 2019


Pure Python, pure state-machine WebSocket implementation

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This repository contains a pure-Python implementation of a WebSocket protocol stack. It's written from the ground up to be embeddable in whatever program you choose to use, ensuring that you can communicate via WebSockets, as defined in RFC6455, regardless of your programming paradigm.

This repository does not provide a parsing layer, a network layer, or any rules about concurrency. Instead, it's a purely in-memory solution, defined in terms of data actions and WebSocket frames. RFC6455 and Compression Extensions for WebSocket via RFC7692 are fully supported.

wsproto supports Python 2.7 and 3.5 or higher.

To install it, just run:

$ pip install wsproto


Let's assume you have some form of network socket available. wsproto client connections automatically generate a HTTP request to initiate the WebSocket handshake. To create a WebSocket client connection:

from wsproto.connection import WSConnection, ConnectionType
from import Request

ws = WSConnection(ConnectionType.CLIENT)
ws.send(Request(host='', target='/'))

To create a WebSocket server connection:

from wsproto.connection import WSConnection, ConnectionType

ws = WSConnection(ConnectionType.SERVER)

Every time you send a message, or call a ping, or simply if you receive incoming data, wsproto might respond with some outgoing data that you have to send:


Both connection types need to receive incoming data:


And wsproto will issue events if the data contains any WebSocket messages or state changes:

for event in
    if isinstance(event, Request):
        # only client connections get this event
    elif isinstance(event, CloseConnection):
        # guess nobody wants to talk to us any more...
    elif isinstance(event, TextMessage):
        print('We got text!',
    elif isinstance(event, BytesMessage):
        print('We got bytes!',

Take a look at our docs for a full list of events <>!


It passes the autobahn test suite completely and strictly in both client and server modes and using permessage-deflate.

If wsaccel is installed (optional), then it will be used to speed things up.

If you want to run the compliance tests, go into the compliance directory and then to test client mode, in one shell run the Autobahn test server:

$ wstest -m fuzzingserver -s ws-fuzzingserver.json

And in another shell run the test client:

$ python

And to test server mode, run the test server:

$ python

And in another shell run the Autobahn test client:

$ wstest -m fuzzingclient -s ws-fuzzingclient.json


Documentation is available at


wsproto welcomes contributions from anyone! Unlike many other projects we are happy to accept cosmetic contributions and small contributions, in addition to large feature requests and changes.

Before you contribute (either by opening an issue or filing a pull request), please read the contribution guidelines.


wsproto is made available under the MIT License. For more details, see the LICENSE file in the repository.


wsproto was created by @jeamland, and is maintained by the python-hyper community.