Connection error: 1006 - connection was closed uncleanly (None)

#code below subscribes to about 2000 rics 
#instrlist is about 2000 

def on_ticks(ws, ticks):
    # Callback to receive ticks.
    for tick in ticks:
        ticker = instrticker_map.get(tick['instrument_token'])
        tick['symbol'] = ticker
        data = json.dumps(tick, cls=DateTimeEncoder)
        socket.send_multipart([ticker.encode(), data.encode()])
        file.write(data)
        file.write("\n")
    file.flush()
    print("Time {}".format(time_now()))


def on_connect(ws, response):
    # Callback on successful connect.
    ws.subscribe(instr_list)

    # Set tick in `full` mode.
    ws.set_mode(ws.MODE_FULL, instr_list)


def on_close(ws, code, reason):
    # On connection close stop the main loop
    # Reconnection will not happen after executing `ws.stop()`
    print("Error - {} - closing socket".format(time_now()))
    ws.stop()
    file.close()


def on_order_update(ws, data):
    pass

def on_message(ws, payload, is_binary):
    pass

def on_reconnect(ws, attempts_count):
    print("Error - %s - on reconnect, attempts %s " % (time_now(), attempts_count))
    pass

def on_noreconnect(ws):
    print("Error - {} - On no reconnect called".format(time_now()))
    pass

def on_error(ws, code, reason):
    print("Error - {} - code {} reason {}".format(time_now(), code, reason))
    pass



# Assign the callbacks.
kws.on_ticks = on_ticks
kws.on_connect = on_connect
kws.on_message = on_message
kws.on_order_update = on_order_update
kws.on_reconnect = on_reconnect
kws.on_noreconnect = on_noreconnect
kws.on_close = on_close
kws.on_error = on_error



# Infinite loop on the main thread. Nothing after this will run.
# You have to use the pre-defined callbacks to manage subscriptions.
kws.connect()