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Features
========
.. currentmodule:: websockets
Feature support matrices summarize which implementations support which features.
.. raw:: html
<style>
.support-matrix-table { width: 100%; }
.support-matrix-table th:first-child { text-align: left; }
.support-matrix-table th:not(:first-child) { text-align: center; width: 15%; }
.support-matrix-table td:not(:first-child) { text-align: center; }
</style>
.. |aio| replace:: :mod:`asyncio` (new)
.. |sync| replace:: :mod:`threading`
.. |sans| replace:: `Sans-I/O`_
.. |leg| replace:: :mod:`asyncio` (legacy)
.. _Sans-I/O: https://sans-io.readthedocs.io/
Both sides
----------
.. table::
:class: support-matrix-table
+------------------------------------+--------+--------+--------+--------+
| | |aio| | |sync| | |sans| | |leg| |
+====================================+========+========+========+========+
| Perform the opening handshake | ✅ | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Enforce opening timeout | ✅ | ✅ | — | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Send a message | ✅ | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Broadcast a message | ✅ | ❌ | — | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Receive a message | ✅ | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Iterate over received messages | ✅ | ✅ | — | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Send a fragmented message | ✅ | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Receive a fragmented message frame | ✅ | ✅ | — | ❌ |
| by frame | | | | |
+------------------------------------+--------+--------+--------+--------+
| Receive a fragmented message after | ✅ | ✅ | — | ✅ |
| reassembly | | | | |
+------------------------------------+--------+--------+--------+--------+
| Force sending a message as Text or | ✅ | ✅ | — | ❌ |
| Binary | | | | |
+------------------------------------+--------+--------+--------+--------+
| Force receiving a message as | ✅ | ✅ | — | ❌ |
| :class:`bytes` or :class:`str` | | | | |
+------------------------------------+--------+--------+--------+--------+
| Send a ping | ✅ | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Respond to pings automatically | ✅ | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Send a pong | ✅ | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Keepalive | ✅ | ✅ | — | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Heartbeat | ✅ | ✅ | — | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Measure latency | ✅ | ✅ | — | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Perform the closing handshake | ✅ | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Enforce closing timeout | ✅ | ✅ | — | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Report close codes and reasons | ✅ | ✅ | ✅ | ❌ |
| from both sides | | | | |
+------------------------------------+--------+--------+--------+--------+
| Compress messages (:rfc:`7692`) | ✅ | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Tune memory usage for compression | ✅ | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Negotiate extensions | ✅ | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Implement custom extensions | ✅ | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Negotiate a subprotocol | ✅ | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Enforce security limits | ✅ | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Log events | ✅ | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+--------+
Server
------
.. table::
:class: support-matrix-table
+------------------------------------+--------+--------+--------+--------+
| | |aio| | |sync| | |sans| | |leg| |
+====================================+========+========+========+========+
| Listen on a TCP socket | ✅ | ✅ | — | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Listen on a Unix socket | ✅ | ✅ | — | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Listen using a preexisting socket | ✅ | ✅ | — | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Encrypt connection with TLS | ✅ | ✅ | — | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Close server on context exit | ✅ | ✅ | — | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Close connection on handler exit | ✅ | ✅ | — | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Shut down server gracefully | ✅ | ✅ | — | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Check ``Origin`` header | ✅ | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Customize subprotocol selection | ✅ | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Configure ``Server`` header | ✅ | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Alter opening handshake request | ✅ | ✅ | ✅ | ❌ |
+------------------------------------+--------+--------+--------+--------+
| Alter opening handshake response | ✅ | ✅ | ✅ | ❌ |
+------------------------------------+--------+--------+--------+--------+
| Force an HTTP response | ✅ | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Perform HTTP Basic Authentication | ✅ | ✅ | ❌ | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Dispatch connections to handlers | ✅ | ✅ | — | ❌ |
+------------------------------------+--------+--------+--------+--------+
Client
------
.. table::
:class: support-matrix-table
+------------------------------------+--------+--------+--------+--------+
| | |aio| | |sync| | |sans| | |leg| |
+====================================+========+========+========+========+
| Connect to a TCP socket | ✅ | ✅ | — | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Connect to a Unix socket | ✅ | ✅ | — | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Connect using a preexisting socket | ✅ | ✅ | — | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Encrypt connection with TLS | ✅ | ✅ | — | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Close connection on context exit | ✅ | ✅ | — | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Reconnect automatically | ✅ | ❌ | — | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Configure ``Origin`` header | ✅ | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Configure ``User-Agent`` header | ✅ | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Modify opening handshake request | ✅ | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Modify opening handshake response | ✅ | ✅ | ✅ | ❌ |
+------------------------------------+--------+--------+--------+--------+
| Connect to non-ASCII IRIs | ✅ | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Follow HTTP redirects | ✅ | ❌ | — | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Perform HTTP Basic Authentication | ✅ | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+--------+
| Connect via HTTP proxy | ✅ | ✅ | — | ❌ |
+------------------------------------+--------+--------+--------+--------+
| Connect via SOCKS5 proxy | ✅ | ✅ | — | ❌ |
+------------------------------------+--------+--------+--------+--------+
Known limitations
-----------------
There is no way to control compression of outgoing frames on a per-frame basis
(`#538`_). If compression is enabled, all frames are compressed.
.. _#538: https://github.com/python-websockets/websockets/issues/538
The server doesn't check the Host header and doesn't respond with HTTP 400 Bad
Request if it is missing or invalid (`#1246`_).
.. _#1246: https://github.com/python-websockets/websockets/issues/1246
The client doesn't support HTTP Digest Authentication (`#784`_).
.. _#784: https://github.com/python-websockets/websockets/issues/784
The client API doesn't attempt to guarantee that there is no more than one
connection to a given IP address in a CONNECTING state. This behavior is
mandated by :rfc:`6455`, section 4.1. However, :func:`~asyncio.client.connect()`
isn't the right layer for enforcing this constraint. It's the caller's
responsibility.
It is possible to send or receive a text message containing invalid UTF-8 with
``send(not_utf8_bytes, text=True)`` and ``not_utf8_bytes = recv(decode=False)``
respectively. As a side effect of disabling UTF-8 encoding and decoding, these
options also disable UTF-8 validation.
|
