FAQ¶

Why is this library slow?¶

The send and validate_utf8 methods are very slow in pure Python. You can disable UTF8 validation in this library (and receive a performance enhancement) with the skip_utf8_validation parameter. If you want to get better performance, please install both numpy and wsaccel, and import them into your project files - these external libraries will automatically be used when available. Note that wsaccel can sometimes cause other issues.

How to solve the “connection is already closed” error?¶

The WebSocketConnectionClosedException, which returns the message “Connection is already closed.”, occurs when a WebSocket function such as send() or recv() is called but the WebSocket connection is already closed. One way to handle exceptions in Python is by using a try/except statement, which allows you to control what your program does if the WebSocket connection is closed when you try to use it. In order to properly carry out further functions with your WebSocket connection after the connection has closed, you will need to reconnect the WebSocket, using connect() or create_connection() (from the _core.py file). The WebSocketApp run_forever() function automatically tries to reconnect when the connection is lost.

What’s going on with the naming of this library?¶

To install this library, you use pip3 install websocket-client, while import websocket imports this library, and PyPi lists the package as websocket_client. Why is it so confusing? To see the original issue about the choice of import websocket, see issue #60 and to read about websocket-client vs. websocket_client, see issue #147

Is WebSocket Compression using the permessage-deflate extension supported?¶

No, RFC 7692 for WebSocket Compression is unfortunately not supported by the websocket-client library at this time. You can view the currently supported WebSocket features in the latest autobahn compliance HTML report, found under the compliance folder. If you use the Sec-WebSocket-Extensions: permessage-deflate header with websocket-client, you will probably encounter errors, such as the ones described in issue #314.

If a connection is re-establish after getting disconnected, does the new connection continue where the previous one dropped off?¶

The answer to this question depends on how the WebSocket server handles new connections. If the server keeps a list of recently dropped WebSocket connection sessions, then it may allow you to recontinue your WebSocket connection where you left off before disconnecting. However, this requires extra effort from the server and may create security issues. For these reasons it is rare to encounter such a WebSocket server. The server would need to identify each connecting client with authentication and keep track of which data was received using a method like TCP’s SYN/ACK. That’s a lot of overhead for a lightweight protocol! Both HTTP and WebSocket connections use TCP sockets, and when a new WebSocket connection is created, it uses a new TCP socket. Therefore, at the TCP layer, the default behavior is to give each WebSocket connection a separate TCP socket. This means the re-established connection after a disconnect is the same as a completely new connection. Another way to think about this is: what should the server do if you create two WebSocket connections from the same client to the same server? The easiest solution for the server is to treat each connection separately, unless the WebSocket uses an authentication method to identify individual clients connecting to the server.

How to disable ssl cert verification?¶

Set the sslopt to {"cert_reqs": ssl.CERT_NONE}. The same sslopt argument is provided for all examples seen below.

WebSocketApp example

ws = websocket.WebSocketApp("wss://echo.websocket.org")
ws.run_forever(sslopt={"cert_reqs": ssl.CERT_NONE})

create_connection example

ws = websocket.create_connection("wss://echo.websocket.org",
  sslopt={"cert_reqs": ssl.CERT_NONE})

WebSocket example

ws = websocket.WebSocket(sslopt={"cert_reqs": ssl.CERT_NONE})
ws.connect("wss://echo.websocket.org")

How to disable hostname verification?¶

Please set sslopt to {"check_hostname": False}. (since v0.18.0)

WebSocketApp example

ws = websocket.WebSocketApp("wss://echo.websocket.org")
ws.run_forever(sslopt={"check_hostname": False})

create_connection example

ws = websocket.create_connection("wss://echo.websocket.org",
  sslopt={"check_hostname": False})

WebSocket example

ws = websocket.WebSocket(sslopt={"check_hostname": False})
ws.connect("wss://echo.websocket.org")

How to enable SNI?¶

SNI support is available for Python 2.7.9+ and 3.2+. It will be enabled automatically whenever possible.

Why don’t I receive all the server’s message(s)?¶

Depending on how long your connection exists, it can help to ping the server to keep the connection alive. See issue #200 for possible solutions.

Using Subprotocols¶

The WebSocket RFC outlines the usage of subprotocols. The subprotocol can be specified as in the example below:

>>> ws = websocket.create_connection("ws://example.com/websocket",
  subprotocols=["binary", "base64"])