Interactive brokers native API. - problem with client. disconnect() - interactive-brokers

Question

I am a noob programmer without a computer science background. I learned to code by trial and error and with online help.
I wrote the following code to download hourly candles from IB TWS.
There is a problem with client.disconnet(). This causes "Error Code: 504 & Error Message: Not connected".
If I remove this line -client.disconnect() from the code and run it again, the error message disappears but API connection stays active. API connection staying active is ok but it seems inefficient way of doing it.
How can it overcome this error message
Thanks
Here is the full code and error message
from ibapi.client import EClient, Contract
from ibapi.wrapper import EWrapper
from ibapi.utils import iswrapper
import datetime
from datetime import date
from datetime import time
from threading import Thread
import time
import socket
import pandas as pd
import talib as ta
import os
class ReadTicker(EWrapper, EClient):
''' Serves as the client and the wrapper '''
def __init__(self, addr, port, client_id):
EClient.__init__(self, self)
# Initialize properties
self.usdpair = {'AUD':'14433401', 'EUR':'12087792', 'GBP':'12087797'}
self.candle_dict = {}
# Connect to TWS
self.connect('127.0.0.1', 7497, 304)
# Launch the client thread
thread = Thread(target=self.run)
thread.start()
#iswrapper
def historicalData(self, req_id, bar):
''' Callback to reqHistoricalData '''
# Add the instrument prices to the dictionary
self.candle_dict['Date'].append(bar.date)
self.candle_dict['Open'].append(bar.open)
self.candle_dict['High'].append(bar.high)
self.candle_dict['Low'].append(bar.low)
self.candle_dict['Close'].append(bar.close)
def error(self, req_id, code, msg):
print('Error Code: {} & Error Message: {}'.format(code, msg))
def main():
start = datetime.time(9, 0, 0)
end = datetime.time(22, 0, 0)
current = datetime.datetime.now().time()
if start <= current <= end:
# Make directory for csv file n create path
if not os.path.exists(r'C:\TWSAPI\samples\Python\Testbed\xlsfiles'):
os.makedirs(r'C:\TWSAPI\samples\Python\Testbed\xlsfiles')
root = r'C:\TWSAPI\samples\Python\Testbed\xlsfiles'
#Create the client and connect to TWS
client = ReadTicker('127.0.0.1', 7497, 304)
time.sleep(10) #Sleep interval to allow time for connection to server
reqId = 2001
for usdpair in client.usdpair:
# Define the contract
usdcontract = Contract()
usdcontract.symbol = usdpair
usdcontract.secType = 'CASH'
usdcontract.exchange = 'IDEALPRO'
usdcontract.currency = "USD"
usdcontract.conId = client.usdpair[usdpair]
print('OHLC Data download for {}USD started.'.format(usdpair))
for v in ['Date','Open', 'High', 'Low', 'Close']:
client.candle_dict[v] = []
now = datetime.datetime.now().strftime("%Y%m%d %H:%M:%S")
client.reqHistoricalData(reqId, usdcontract, now, '7 D', '1 hour', 'TRADES', False, 1, False, [])
reqId += 1
time.sleep(5)
df = pd.DataFrame(client.candle_dict, columns=['Date', 'Open', 'High', 'Low', 'Close'])
df['Date'] = pd.to_datetime(df['Date'])
df.to_csv(root + '/'+ usdpair + 'USD' + '.csv', encoding='utf-8', index= False)
client.candle_dict.clear()
client.disconnect()
else:
print('Trading time is over')
if __name__ == '__main__':
main()
Error Message: is as follows:
Error Code: 2104 & Error Message: Market data farm connection is OK:uscrypto
Error Code: 2104 & Error Message: Market data farm connection is OK:usfarm.nj
Error Code: 2104 & Error Message: Market data farm connection is OK:hfarm
Error Code: 2104 & Error Message: Market data farm connection is OK:cashfarm
Error Code: 2106 & Error Message: HMDS data farm connection is OK:euhmds
Error Code: 2106 & Error Message: HMDS data farm connection is OK:cashhmds
Error Code: 2106 & Error Message: HMDS data farm connection is OK:hkhmds
Error Code: 2106 & Error Message: HMDS data farm connection is OK:fundfarm
Error Code: 2106 & Error Message: HMDS data farm connection is OK:ushmds
Error Code: 2158 & Error Message: Sec-def data farm connection is OK:secdefhk
OHLC Data download for AUDUSD started.
Error Code: 162 & Error Message: Historical Market Data Service error message:No historical market data for AUD/CASH#FXSUBPIP Last 3600
OHLC Data download for EURUSD started.
Error Code: 504 & Error Message: Not connected
unhandled exception in EReader thread
Traceback (most recent call last):
File "C:\Users\venky\anaconda3\lib\site-packages\ibapi-9.76.1-py3.8.egg\ibapi\reader.py", line 34, in run
data = self.conn.recvMsg()
File "C:\Users\venky\anaconda3\lib\site-packages\ibapi-9.76.1-py3.8.egg\ibapi\connection.py", line 99, in recvMsg
buf = self._recvAllMsg()
File "C:\Users\venky\anaconda3\lib\site-packages\ibapi-9.76.1-py3.8.egg\ibapi\connection.py", line 119, in _recvAllMsg
buf = self.socket.recv(4096)
OSError: [WinError 10038] An operation was attempted on something that is not a socket
OHLC Data download for GBPUSD started.
Error Code: 504 & Error Message: Not connected
PS C:\TWSAPI\samples\Python\Testbed>