Python socketio example to connect to cryptocompare

Question

I am trying to connect to Cryptocompare's websocket stream using socketIO from a Python client. This is proving to be challenging. Here is some sample Python code:

from socketIO_client import SocketIO

print "connecting to server"
socketIO = SocketIO('https://streamer.cryptocompare.com/',443, transports=['websocket'])
print "Connected"

However, I am not able to connect, whatever I do. In fact, this is the result of that connect

connecting to server
Traceback (most recent call last):
  File "test.py", line 4, in <module>
socketIO = SocketIO('https://streamer.cryptocompare.com/',443, transports=['websocket'])
  File "/usr/local/lib/python2.7/site-packages/socketIO_client/__init__.py", line 353, in __init__
resource, hurry_interval_in_seconds, **kw)
  File "/usr/local/lib/python2.7/site-packages/socketIO_client/__init__.py", line 54, in __init__
self._transport
  File "/usr/local/lib/python2.7/site-packages/socketIO_client/__init__.py", line 62, in _transport
self._engineIO_session = self._get_engineIO_session()
  File "/usr/local/lib/python2.7/site-packages/socketIO_client/__init__.py", line 76, in _get_engineIO_session
transport.recv_packet())
StopIteration

Wrapping the above code in a try-catch and printing the exception yields no extra information. Any help would be greatly appreciated.

Answer 1

The socketIO_client library does not seem to support the XHR polling protocol that is used by cryptocompare. I got it to work by overriding the method recv_packet in the socketIO_client.transports.XHR_PollingTransport class.

import logging
import socketIO_client
from socketIO_client.transports import get_response
from socketIO_client.parsers import get_byte, _read_packet_text, parse_packet_text

from requests.exceptions import ConnectionError

# extra function to support XHR1 style protocol
def _new_read_packet_length(content, content_index):
    packet_length_string = ''
    while get_byte(content, content_index) != ord(':'):
        byte = get_byte(content, content_index)
        packet_length_string += chr(byte)
        content_index += 1
    content_index += 1
    return content_index, int(packet_length_string)

def new_decode_engineIO_content(content):
    content_index = 0
    content_length = len(content)
    while content_index < content_length:
        try:
            content_index, packet_length = _new_read_packet_length(
                content, content_index)
        except IndexError:
            break
        content_index, packet_text = _read_packet_text(
            content, content_index, packet_length)
        engineIO_packet_type, engineIO_packet_data = parse_packet_text(
            packet_text)
        yield engineIO_packet_type, engineIO_packet_data

def new_recv_packet(self):
    params = dict(self._params)
    params['t'] = self._get_timestamp()
    response = get_response(
        self.http_session.get,
        self._http_url,
        params=params,
        **self._kw_get)
    for engineIO_packet in new_decode_engineIO_content(response.content):
        engineIO_packet_type, engineIO_packet_data = engineIO_packet
        yield engineIO_packet_type, engineIO_packet_data

setattr(socketIO_client.transports.XHR_PollingTransport, 'recv_packet', new_recv_packet)

logging.basicConfig(level=logging.DEBUG)

try:
    socket = socketIO_client.SocketIO('https://streamer.cryptocompare.com')
    socket.emit('SubAdd', { 'subs': ['0~Kraken~BTC~USD'] });
    socket.wait()
except ConnectionError:
    print('The server is down. Try again later.')

The solution is heavily based on this github comment: https://github.com/invisibleroads/socketIO-client/issues/129#issuecomment-330058318