Tornado websockets supporting binary part 2

Question

I am attempting to pass binary data over websockets, more specifically compressed strings over websockets. In my current setup I use tornado as the server with a websocket client transmitting the binary data. The binary data is formed by compressing the data with zlib. Both client and server are as simple as they get and are shown below.

Server:

import tornado.websocket
import tornado.httpserver
import tornado.ioloop
import tornado.web

class WebSocketServer(tornado.websocket.WebSocketHandler):
    def open(self):
        print 'OPEN'

    def on_message(self, message):
        print 'len = {}'.format(len(message))
        print 'GOT MESSAGE: {}'.format(message.decode('zlib'))

    def on_close(self):
        print 'CLOSE'

app = tornado.web.Application([
        (r'/', WebSocketServer)
    ])
http_server = tornado.httpserver.HTTPServer(app)
http_server.listen(9500)
tornado.ioloop.IOLoop.instance().start()

Client:

import websocket

host = 'localhost'
port_ws = 9500
ws = websocket.create_connection('ws://{}:{}/'.format(host, port_ws))
message = 'this is my message'.encode('zlib')
print 'Length of message is {}'.format(len(message))
ws.send(message)

The client does not throw any errors, it prints out that the message: Length of message is 24. The message is encoded as a str as per the zlib standard. The server on the other end does not show that it received any messages, it just understands that a client had connected, and then disconnected. Does anyone know where the problem is? I am not sure if the problem lays within tornado or the websockets library. Any suggestions?

---

EDIT: In response to the comment below (@plg), I modified the scripts above to show that:

1. Non-encoded messages can be send from client to the tornado server
2. Tornado can reply with an encoded message

Server:

import tornado.websocket
import tornado.httpserver
import tornado.ioloop
import tornado.web

class WebSocketServer(tornado.websocket.WebSocketHandler):
    def open(self):
        print 'OPEN'

    def on_message(self, message):
        print 'len = {}'.format(len(message))
        print 'GOT MESSAGE: {}'.format(message)
        self.write_message(message.encode('zlib'))

    def on_close(self):
        print 'CLOSE'

app = tornado.web.Application([
        (r'/', WebSocketServer)
    ])
http_server = tornado.httpserver.HTTPServer(app)
http_server.listen(9500)
tornado.ioloop.IOLoop.instance().start()

Client:

import websocket

host = 'localhost'
port_ws = 9500
ws = websocket.create_connection('ws://{}:{}/'.format(host, port_ws))
#message = 'this is my message'.encode('zlib')
message = 'this is my message'
print 'Length of message is {}'.format(len(message))
ws.send(message)
assert ws.recv().decode('zlib') == message

The system works just fine. The assert does not throw an error. The decoded message matches the send message. So I guess there is a problem with either:

1. Sending an encoded message from the client
2. Tornado receiving encoded messages

To be quite honest, I do believe that the first option is more probable than tornado. In my opinion, I believe tornado would alert me if an incoming message is not properly decoded as per the websocket standard. Any more suggestions?

---

EDIT: More development on who is at fault. Instead of using my own server to relay back and fourth my connection, I relayed the connection to ws://echo.websocket.org/. My testing application is as shows:

import websocket

host = 'localhost'
port_ws = 9500
ws = websocket.create_connection('ws://echo.websocket.org/')
message = 'this is my message'
ws.send(message.encode('zlib'))
got = ws.recv().decode('zlib')
print 'GOT: {}'.format(got)
assert got == message

This actually passed the test, the data was received just fine. So I guess there is something wrong with tornado receiving the data?

Answer 1

After looking though the source code of the websocket library, I found that by default it is formatting the packets as text. By changing the line:

ws.send('message')
# to:
ws.send('message', opcode=websocket.ABNF.OPCODE_BINARY)
# or better yet:
ws.send_binary('message')

The packet will be sent over just fine. Tornado I guess was just ignoring the fake binary packets since they were marked as text and contained binary.