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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`
.. |sync| replace:: :mod:`threading`
.. |sans| replace:: `Sans-I/O`_
Both sides
----------
.. table::
:class: support-matrix-table
+------------------------------------+--------+--------+--------+
| | |aio| | |sync| | |sans| |
+====================================+========+========+========+
| Perform the opening handshake | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+
| Send a message | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+
| Receive a message | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+
| Iterate over received messages | ✅ | ✅ | ❌ |
+------------------------------------+--------+--------+--------+
| Send a fragmented message | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+
| Receive a fragmented message after | ✅ | ✅ | ❌ |
| reassembly | | | |
+------------------------------------+--------+--------+--------+
| Receive a fragmented message frame | ❌ | ✅ | ✅ |
| by frame (`#479`_) | | | |
+------------------------------------+--------+--------+--------+
| Send a ping | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+
| Respond to pings automatically | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+
| Send a pong | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+
| Perform the closing handshake | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+
| 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 | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+
| Enforce opening timeout | ✅ | ✅ | — |
+------------------------------------+--------+--------+--------+
| Enforce closing timeout | ✅ | ✅ | — |
+------------------------------------+--------+--------+--------+
| Keepalive | ✅ | ❌ | — |
+------------------------------------+--------+--------+--------+
| Heartbeat | ✅ | ❌ | — |
+------------------------------------+--------+--------+--------+
Server
------
.. table::
:class: support-matrix-table
+------------------------------------+--------+--------+--------+
| | |aio| | |sync| | |sans| |
+====================================+========+========+========+
| 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 | ❌ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+
| Perform HTTP Basic Authentication | ✅ | ❌ | ❌ |
+------------------------------------+--------+--------+--------+
| Perform HTTP Digest Authentication | ❌ | ❌ | ❌ |
+------------------------------------+--------+--------+--------+
| Force HTTP response | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+
Client
------
.. table::
:class: support-matrix-table
+------------------------------------+--------+--------+--------+
| | |aio| | |sync| | |sans| |
+====================================+========+========+========+
| 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 | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+
| Alter opening handshake request | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+
| Connect to non-ASCII IRIs | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+
| Perform HTTP Basic Authentication | ✅ | ✅ | ✅ |
+------------------------------------+--------+--------+--------+
| Perform HTTP Digest Authentication | ❌ | ❌ | ❌ |
| (`#784`_) | | | |
+------------------------------------+--------+--------+--------+
| Follow HTTP redirects | ✅ | ❌ | — |
+------------------------------------+--------+--------+--------+
| Connect via a HTTP proxy (`#364`_) | ❌ | ❌ | — |
+------------------------------------+--------+--------+--------+
| Connect via a SOCKS5 proxy | ❌ | ❌ | — |
| (`#475`_) | | | |
+------------------------------------+--------+--------+--------+
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.
The server doesn't check the Host header and respond with a HTTP 400 Bad Request
if it is missing or invalid (`#1246`).
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`_. However, :func:`~client.connect()` isn't the right
layer for enforcing this constraint. It's the caller's responsibility.