websockets for python and twisted
August 7, 2010
RestMQ has a unique endpoint for consumers which uses websockets. As such, I implemented websockets for cyclone and twisted some time ago. Last July there was an upgrade to the protocol to implement a ‘secure’ handshake. This new spec broke most of the implementations because it mixed the upgrade headers part and the first 8 bytes from the content.
I’ve upgraded both cyclone and txwebsockets to understand the ‘old’ spec (hixie 75) and the new one. Basically the handshake involves extracting numbers from two headers (Sec-Websocket-Key1 and Sec-Websocket-Key2), dividing the resulting number by the number of spaces, concatenating them with 8 bytes read from the socket and sending back the md5 digest of this mess back after the new headers. Code to test and calculate the handshake from the headers value can be found here .