February 19, 2012

WebSocket RFC 6455 Handshake

I think I got the request/response bit figured out (it was actually simpler than the draft 76 method). This is my test using headers from the RFC document:

from hashlib import sha1
from base64 import b64encode

WS13_GUID = b'258EAFA5-E914-47DA-95CA-C5AB0DC85B11'

b'GET /chat HTTP/1.1\r\n'
b'Host: server.example.com\r\n'
b'Upgrade: websocket\r\n'
b'Connection: Upgrade\r\n'
b'Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==\r\n'
b'Origin: http://example.com\r\n'
b'Sec-WebSocket-Protocol: chat, superchat\r\n'
b'Sec-WebSocket-Version: 13\r\n'

b'HTTP/1.1 101 Switching Protocols\r\n'
b'Upgrade: websocket\r\n'
b'Connection: Upgrade\r\n'
b'Sec-WebSocket-Accept: {}\r\n'
b'Sec-WebSocket-Protocol: chat\r\n'


def parse_request(request):
req = {}
lines = request.split(b'\r\n')
line = lines.pop(0)
items = line.split(b'\x20',2)
if len(items) != 3:
raise BaseException('Malformed WebSocket Request Method.')
req[b'method'] = items[0]
req[b'request_uri'] = items[1]
req[b'http_version'] = items[2]
for line in lines:
if line:
parts = line.split(b':\x20', 1)
req[parts[0].lower()] = parts[1]
return req

if __name__ == '__main__':
req = parse_request(REQUEST)
salted_key = req[b'sec-websocket-key'] + WS13_GUID
sec_ws_accept = b64encode(sha1(salted_key).digest())
assert(sec_ws_accept == CORRECT_ACCEPT)
print RESPONSE.format(sec_ws_accept)

Step two is to get the VERY DIFFERENT message protocol working.


Joe said...

Thank you for putting this together. I think a lot of people are capable of adventuring through text but unlikely to open a telnet terminal.

I'm having a lot of fun developing on top of Miniboa.

Jim said...

Thanks Joe!

I'm happy that you find Miniboa useful.