how to limit tornado websocket message size

Question

I have written a websocket server in tornado and on_message method is called when a message is received. The problem is, the message size is unlimited by defual

Answer 1

Since version 4.5 Tornado will close the connection automatically if it receives more than 10 MiB of data in a single websocket frame (message). So, you don't have to worry about someone sending huge data in a single message. You can see this in the source code. It's also mentioned in the docs of WebsocketHandler in the second-last paragraph.

If you'd like to change the default frame limit you can pass your Application class an argument called websocket_max_message_size with the size in bytes.

app = tornado.web.Application(
      # your handlers etc,
      websocket_max_message_size=128
)