Changelog - websockets 10.3 documentation
Description: Backwards-compatibility policy: websockets is intended for production use. Therefore, stability is a goal. websockets also aims at providing the best API for WebSocket in Python. While we value sta...

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# Changelog

## Backwards-compatibility policy

websockets is intended for production use. Therefore, stability is a goal.

websockets also aims at providing the best API for WebSocket in Python.

While we value stability, we value progress more. When an improvement requires changing a public API, we make the change and document it in this changelog.

When possible with reasonable effort, we preserve backwards-compatibility for five years after the release that introduced the change.

When a release contains backwards-incompatible API changes, the major version is increased, else the minor version is increased. Patch versions are only for fixing regressions shortly after a release.

Only documented APIs are public. Undocumented APIs are considered private. They may change at any time.

## 10.3

April 17, 2022

### Backwards-incompatible changes

The `exception` attribute of `Request` and `Response` is deprecated.

Use the `handshake_exc` attribute of `ServerConnection` and `ClientConnection` instead.

See Integrate the Sans-I/O layer for details.

### Improvements

- Reduced noise in logs when `ssl` or `zlib` raise exceptions.

## 10.2

February 21, 2022

### Improvements

- Made compression negotiation more lax for compatibility with Firefox.

- Improved FAQ and quick start guide.

### Bug fixes

- Fixed backwards-incompatibility in 10.1 for connection handlers created with `functools.partial()`.

- Avoided leaking open sockets when `connect()` is canceled.

## 10.1

November 14, 2021

### New features

- Added a tutorial.

- Made the second parameter of connection handlers optional. It will be deprecated in the next major release. The request path is available in the `path` attribute of the first argument.

  If you implemented the connection handler of a server as:

      async def handler(request, path):
          ...

  You should replace it by:

      async def handler(request):
          path = request.path  # if handler() uses the path argument
          ...

- Added `python -m websockets --version`.

### Improvements

- Added wheels for Python 3.10, PyPy 3.7, and for more platforms.

- Reverted optimization of default compression settings for clients, mainly to avoid triggering bugs in poorly implemented servers like AWS API Gateway.

- Mirrored the entire `Server` API in `WebSocketServer`.

- Improved performance for large messages on ARM processors.

- Documented how to auto-reload on code changes in development.

### Bug fixes

- Avoided half-closing TCP connections that are already closed.

## 10.0

September 9, 2021

### Backwards-incompatible changes

websockets 10.0 requires Python ≥ 3.7.

websockets 9.1 is the last version supporting Python 3.6.

The `loop` parameter is deprecated from all APIs.

This reflects a decision made in Python 3.8. See the release notes of Python 3.10 for details.

The `loop` parameter is also removed from `WebSocketServer`. This should be transparent.

`connect()` times out after 10 seconds by default.

You can adjust the timeout with the `open_timeout` parameter. Set it to `None` to disable the timeout entirely.

The `legacy_recv` option is deprecated.

See the release notes of websockets 3.0 for details.

The signature of `ConnectionClosed` changed.

If you raise `ConnectionClosed` or a subclass, rather than catch them when websockets raises them, you must change your code.

A `msg` parameter was added to `InvalidURI`.

If you raise `InvalidURI`, rather than catch it when websockets raises it, you must change your code.

### New features

websockets 10.0 introduces a Sans-I/O API for easier integration in third-party libraries.

If you’re integrating websockets in a library, rather than just using it, look at the Sans-I/O integration guide.

- Added compatibility with Python 3.10.

- Added `broadcast()` to send a message to many clients.

- Added support for reconnecting automatically by using `connect()` as an asynchronous iterator.

- Added `open_timeout` to `connect()`.

- Documented how to integrate with Django.

- Documented how to deploy websockets in production, with several options.

- Documented how to authenticate connections.

- Documented how to broadcast messages to many connections.

### Improvements

- Improved logging. See the logging guide.

- Optimized default compression settings to reduce memory usage.

- Optimized processing of client-to-server messages when the C extension isn’t available.

- Supported relative redirects in `connect()`.

- Handled TCP connection drops during the opening handshake.

- Made it easier to customize authentication with `check_credentials()`.

- Provided additional information in `ConnectionClosed` exceptions.

- Clarified several exceptions or log messages.

- Restructured documentation.

- Improved API documentation.

- Extended FAQ.

### Bug fixes

- Avoided a crash when receiving a ping while the connection is closing.

## 9.1

May 27, 2021

### Security fix

websockets 9.1 fixes a security issue introduced in 8.0.

Version 8.0 was vulnerable to timing attacks on HTTP Basic Auth passwords (CVE-2021-33880).

## 9.0.2

May 15, 2021

### Bug fixes

- Restored compatibility of `python -m websockets` with Python < 3.9.

- Restored compatibility with mypy.

## 9.0.1

May 2, 2021

### Bug fixes

- Fixed issues with the packaging of the 9.0 release.

## 9.0

May 1, 2021

### Backwards-incompatible changes

Several modules are moved or deprecated.

Aliases provide compatibility for all previously public APIs according to the backwards-compatibility policy

- `Headers` and `MultipleValuesError` are moved from `websockets.http` to `websockets.datastructures`. If you’re using them, you should adjust the import path.

- The `client`, `server`, `protocol`, and `auth` modules were moved from the `websockets` package to a `websockets.legacy` sub-package. Despite the name, they’re still fully supported.

- The `framing`, `handshake`, `headers`, `http`, and `uri` modules in the `websockets` package are deprecated. These modules provided low-level APIs for reuse by other projects, but they didn’t reach that goal. Keeping these APIs public makes it more difficult to improve websockets.

These changes pave the path for a refactoring that should be a transparent upgrade for most uses and facilitate integration by other projects.

Convenience imports from `websockets` are performed lazily.

While Python supports this, tools relying on static code analysis don’t. This breaks autocompletion in an IDE or type checking with mypy.

If you depend on such tools, use the real import paths, which can be found in the API documentation, for example:

    from websockets.client import connect
    from websockets.server import serve

### New features

- Added compatibility with Python 3.9.

### Improvements

- Added support for IRIs in addition to URIs.

- Added close codes 1012, 1013, and 1014.

- Raised an error when passing a `dict` to `send()`.

- Improved error reporting.

### Bug fixes

- Fixed sending fragmented, compressed messages.

- Fixed `Host` header sent when connecting to an IPv6 address.

- Fixed creating a client or a server with an existing Unix socket.

- Aligned maximum cookie size with popular web browsers.

- Ensured cancellation always propagates, even on Python versions where `CancelledError` inherits `Exception`.

## 8.1

November 1, 2019

### New features

- Added compatibility with Python 3.8.

## 8.0.2

July 31, 2019

### Bug fixes

- Restored the ability to pass a socket with the `sock` parameter of `serve()`.

- Removed an incorrect assertion when a connection drops.

## 8.0.1

July 21, 2019

### Bug fixes

- Restored the ability to import `WebSocketProtocolError` from `websockets`.

## 8.0

July 7, 2019

### Backwards-incompatible changes

websockets 8.0 requires Python ≥ 3.6.

websockets 7.0 is the last version supporting Python 3.4 and 3.5.

`process_request` is now expected to be a coroutine.

If you’re passing a `process_request` argument to `serve()` or `WebSocketServerProtocol`, or if you’re overriding `process_request()` in a subclass, define it with `async def` instead of `def`. Previously, both were supported.

For backwards compatibility, functions are still accepted, but mixing functions and coroutines won’t work in some inheritance scenarios.

`max_queue` must be `None` to disable the limit.

If you were setting `max_queue=0` to make the queue of incoming messages unbounded, change it to `max_queue=None`.

The `host`, `port`, and `secure` attributes of `WebSocketCommonProtocol` are deprecated.

Use `local_address` in servers and `remote_address` in clients instead of `host` and `port`.

`WebSocketProtocolError` is renamed to `ProtocolError`.

An alias provides backwards compatibility.

`read_response()` now returns the reason phrase.

If you’re using this low-level API, you must change your code.

### New features

- Added `basic_auth_protocol_factory()` to enforce HTTP Basic Auth on the server side.

- `connect()` handles redirects from the server during the handshake.

- `connect()` supports overriding `host` and `port`.

- Added `unix_connect()` for connecting to Unix sockets.

- Added support for asynchronous generators in `send()` to generate fragmented messages incrementally.

- Enabled readline in the interactive client.

- Added type hints (PEP 484).

- Added a FAQ to the documentation.

- Added documentation for extensions.

- Documented how to optimize memory usage.

### Improvements

- `send()`, `ping()`, and `pong()` support bytes-like types `bytearray` and `memoryview` in addition to `bytes`.

- Added `ConnectionClosedOK` and `ConnectionClosedError` subclasses of `ConnectionClosed` to tell apart normal connection termination from errors.

- Changed `WebSocketServer.close()` to perform a proper closing handshake instead of failing the connection.

- Improved error messages when HTTP parsing fails.

- Improved API documentation.

### Bug fixes

- Prevented spurious log messages about `ConnectionClosed` exceptions in keepalive ping task. If you were using `ping_timeout=None` as a workaround, you can remove it.

- Avoided a crash when a `extra_headers` callable returns `None`.

## 7.0

November 1, 2018

### Backwards-incompatible changes

Keepalive is enabled by default.

websockets now sends Ping frames at regular intervals and closes the connection if it doesn’t receive a matching Pong frame. See `WebSocketCommonProtocol` for details.

Termination of connections by `WebSocketServer.close()` changes.

Previously, connections handlers were canceled. Now, connections are closed with close code 1001 (going away).

From the perspective of the connection handler, this is the same as if the remote endpoint was disconnecting. This removes the need to prepare for `CancelledError` in connection handlers.

You can restore the previous behavior by adding the following line at the beginning of connection handlers:

    def handler(websocket, path):
        closed = asyncio.ensure_future(websocket.wait_closed())
        closed.add_done_callback(lambda task: task.cancel())

Calling `recv()` concurrently raises a `RuntimeError`.

Concurrent calls lead to non-deterministic behavior because there are no guarantees about which coroutine will receive which message.

The `timeout` argument of `serve()` and `connect()` is renamed to `close_timeout` .

This prevents confusion with `ping_timeout`.

For backwards compatibility, `timeout` is still supported.

The `origins` argument of `serve()` changes.

Include `None` in the list rather than `''` to allow requests that don’t contain an Origin header.

Pending pings aren’t canceled when the connection is closed.

A ping — as in `ping = await websocket.ping()` — for which no pong was received yet used to be canceled when the connection is closed, so that `await ping` raised `CancelledError`.

Now `await ping` raises `ConnectionClosed` like other public APIs.

### New features

- Added `process_request` and `select_subprotocol` arguments to `serve()` and `WebSocketServerProtocol` to facilitate customization of `process_request()` and `select_subprotocol()`.

- Added support for sending fragmented messages.

- Added the `wait_closed()` method to protocols.

- Added an interactive client: `python -m websockets <uri>`.

### Improvements

- Improved handling of multiple HTTP headers with the same name.

- Improved error messages when a required HTTP header is missing.

### Bug fixes

- Fixed a data loss bug in `recv()`: canceling it at the wrong time could result in messages being dropped.

## 6.0

July 16, 2018

### Backwards-incompatible changes

The `Headers` class is introduced and several APIs are updated to use it.

- The `request_headers` argument of `process_request()` is now a `Headers` instead of an `http.client.HTTPMessage`.

- The `request_headers` and `response_headers` attributes of `WebSocketCommonProtocol` are now `Headers` instead of `http.client.HTTPMessage`.

- The `raw_request_headers` and `raw_response_headers` attributes of `WebSocketCommonProtocol` are removed. Use `raw_items()` instead.

- Functions defined in the `handshake` module now receive `Headers` in argument instead of `get_header` or `set_header` functions. This affects libraries that rely on low-level APIs.

- Functions defined in the `http` module now return HTTP headers as `Headers` instead of lists of `(name, value)` pairs.

Since `Headers` and `http.client.HTTPMessage` provide similar APIs, much of the code dealing with HTTP headers won’t require changes.

### New features

- Added compatibility with Python 3.7.

## 5.0.1

May 24, 2018

### Bug fixes

- Fixed a regression in 5.0 that broke some invocations of `serve()` and `connect()`.

## 5.0

May 22, 2018

### Security fix

websockets 5.0 fixes a security issue introduced in 4.0.

Version 4.0 was vulnerable to denial of service by memory exhaustion because it didn’t enforce `max_size` when decompressing compressed messages (CVE-2018-1000518).

### Backwards-incompatible changes

A `user_info` field is added to the return value of `parse_uri` and `WebSocketURI`.

If you’re unpacking `WebSocketURI` into four variables, adjust your code to account for that fifth field.

### New features

- `connect()` performs HTTP Basic Auth when the URI contains credentials.

- `unix_serve()` can be used as an asynchronous context manager on Python ≥ 3.5.1.

- Added the `closed` property to protocols.

- Added new examples in the documentation.

### Improvements

- Iterating on incoming messages no longer raises an exception when the connection terminates with close code 1001 (going away).

- A plain HTTP request now receives a 426 Upgrade Required response and doesn’t log a stack trace.

- If a `ping()` doesn’t receive a pong, it’s canceled when the connection is closed.

- Reported the cause of `ConnectionClosed` exceptions.

- Stopped logging stack traces when the TCP connection dies prematurely.

- Prevented writing to a closing TCP connection during unclean shutdowns.

- Made connection termination more robust to network congestion.

- Prevented processing of incoming frames after failing the connection.

- Updated documentation with new features from Python 3.6.

- Improved several sections of the documentation.

### Bug fixes

- Prevented `TypeError` due to missing close code on connection close.

- Fixed a race condition in the closing handshake that raised `InvalidState`.

## 4.0.1

November 2, 2017

### Bug fixes

- Fixed issues with the packaging of the 4.0 release.

## 4.0

November 2, 2017

### Backwards-incompatible changes

websockets 4.0 requires Python ≥ 3.4.

websockets 3.4 is the last version supporting Python 3.3.

Compression is enabled by default.

In August 2017, Firefox and Chrome support the permessage-deflate extension, but not Safari and IE.

Compression should improve performance but it increases RAM and CPU use.

If you want to disable compression, add `compression=None` when calling `serve()` or `connect()`.

The `state_name` attribute of protocols is deprecated.

Use `protocol.state.name` instead of `protocol.state_name`.

### New features

- `WebSocketCommonProtocol` instances can be used as asynchronous iterators on Python ≥ 3.6. They yield incoming messages.

- Added `unix_serve()` for listening on Unix sockets.

- Added the `sockets` attribute to the return value of `serve()`.

- Allowed `extra_headers` to override `Server` and `User-Agent` headers.

### Improvements

- Reorganized and extended documentation.

- Rewrote connection termination to increase robustness in edge cases.

- Reduced verbosity of “Failing the WebSocket connection” logs.

### Bug fixes

- Aborted connections if they don’t close within the configured `timeout`.

- Stopped leaking pending tasks when `cancel()` is called on a connection while it’s being closed.

## 3.4

August 20, 2017

### Backwards-incompatible changes

`InvalidStatus` is replaced by `InvalidStatusCode`.

This exception is raised when `connect()` receives an invalid response status code from the server.

### New features

- `serve()` can be used as an asynchronous context manager on Python ≥ 3.5.1.

- Added support for customizing handling of incoming connections with `process_request()`.

- Made read and write buffer sizes configurable.

### Improvements

- Renamed `serve()` and `connect()`’s `klass` argument to `create_protocol` to reflect that it can also be a callable. For backwards compatibility, `klass` is still supported.

- Rewrote HTTP handling for simplicity and performance.

- Added an optional C extension to speed up low-level operations.

### Bug fixes

- Providing a `sock` argument to `connect()` no longer crashes.

## 3.3

March 29, 2017

### New features

- Ensured compatibility with Python 3.6.

### Improvements

- Reduced noise in logs caused by connection resets.

### Bug fixes

- Avoided crashing on concurrent writes on slow connections.

## 3.2

August 17, 2016

### New features

- Added `timeout`, `max_size`, and `max_queue` arguments to `connect()` and `serve()`.

### Improvements

- Made server shutdown more robust.

## 3.1

April 21, 2016

### New features

- Added flow control for incoming data.

### Bug fixes

- Avoided a warning when closing a connection before the opening handshake.

## 3.0

December 25, 2015

### Backwards-incompatible changes

`recv()` now raises an exception when the connection is closed.

`recv()` used to return `None` when the connection was closed. This required checking the return value of every call:

    message = await websocket.recv()
    if message is None:
        return

Now it raises a `ConnectionClosed` exception instead. This is more Pythonic. The previous code can be simplified to:

    message = await websocket.recv()

When implementing a server, there’s no strong reason to handle such exceptions. Let them bubble up, terminate the handler coroutine, and the server will simply ignore them.

In order to avoid stranding projects built upon an earlier version, the previous behavior can be restored by passing `legacy_recv=True` to `serve()`, `connect()`, `WebSocketServerProtocol`, or `WebSocketClientProtocol`.

### New features

- `connect()` can be used as an asynchronous context manager on Python ≥ 3.5.1.

- `ping()` and `pong()` support data passed as `str` in addition to `bytes`.

- Made `state_name` attribute on protocols a public API.

### Improvements

- Updated documentation with `await` and `async` syntax from Python 3.5.

- Worked around an `asyncio` bug affecting connection termination under load.

- Improved documentation.

## 2.7

November 18, 2015

### New features

- Added compatibility with Python 3.5.

### Improvements

- Refreshed documentation.

## 2.6

August 18, 2015

### New features

- Added `local_address` and `remote_address` attributes on protocols.

- Closed open connections with code 1001 when a server shuts down.

### Bug fixes

- Avoided TCP fragmentation of small frames.

## 2.5

July 28, 2015

### New features

- Provided access to handshake request and response HTTP headers.

- Allowed customizing handshake request and response HTTP headers.

- Added support for running on a non-default event loop.

### Improvements

- Improved documentation.

- Sent a 403 status code instead of 400 when request Origin isn’t allowed.

- Clarified that the closing handshake can be initiated by the client.

- Set the close code and reason more consistently.

- Strengthened connection termination.

### Bug fixes

- Canceling `recv()` no longer drops the next message.

## 2.4

January 31, 2015

### New features

- Added support for subprotocols.

- Added `loop` argument to `connect()` and `serve()`.

## 2.3

November 3, 2014

### Improvements

- Improved compliance of close codes.

## 2.2

July 28, 2014

### New features

- Added support for limiting message size.

## 2.1

April 26, 2014

### New features

- Added `host`, `port` and `secure` attributes on protocols.

- Added support for providing and checking Origin.

## 2.0

February 16, 2014

### Backwards-incompatible changes

`send()`, `ping()`, and `pong()` are now coroutines.

They used to be functions.

Instead of:

    websocket.send(message)

you must write:

    await websocket.send(message)

### New features

- Added flow control for outgoing data.

## 1.0

November 14, 2013

### New features

- Initial public release.