Port Forwaring

import socket
import sys
import threading
import time
import math
import functools
from operator import itemgetter
 
settings = list()
weight_list = list()
minus_list = list()
 
def __getitem__(self, row):
    return self.data[row]
 
def gcd(L):
    return functools.reduce(math.gcd, L)
 
def main(setup, error):
    sys.stderr = open(error, 'a')
 
    for line in open(setup):
        parts = line.split()
        weight_list.append([int(parts[0]), parts[1], int(parts[2]), int(parts[3]), int(parts[4]), int(parts[5])])
    settings = list(weight_list)
    for i in range(len(settings)):
        minus_list.append(settings[i][5])
    minus = gcd(minus_list)
    settings.sort(key=itemgetter(5), reverse=True)
    setting = tuple(settings[0])
    settings[0][5] = settings[0][5]-minus
    threading.Thread(target=server, args=(settings, setup, minus, setting)).start()
 
def server(settings, setup, minus, setting):
        try:
                dock_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
                dock_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
                dock_socket.bind(('', 80))
                dock_socket.listen(5)
                while True:
                        client_socket = dock_socket.accept()
                        server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
                        server_socket.connect((setting[1], 80))
                        threading.Thread(target=forward, args=(client_socket, server_socket)).start()
                        threading.Thread(target=forward, args=(server_socket, client_socket)).start()
        finally:
                if settings[0][5]<=0:
                        weight_list = list()
                        for line in open(setup):
                                parts = line.split()
                                weight_list.append([int(parts[0]), parts[1], int(parts[2]), int(parts[3]), int(parts[4]), int(parts[5])])
                        settings = weight_list
                        for i in range(len(settings)):
                                minus_list.append(settings[i][5])
                        minus = gcd(minus_list)
                settings.sort(key=itemgetter(5), reverse=True)
                setting = tuple(settings[0])
                settings[0][5] = settings[0][5]-minus
                threading.Thread(target=server, args=(settings, setup, minus, setting)).start()
 
def forward(source, destination):
        string = ''
        print('work')
        while string:
                string = source.recv(4096)
                if string:
                        destination.sendall(string)
                else:
                        source.shutdown(socket.SHUT_RD)
                        destination.shutdown(socket.SHUT_WR)
 
if __name__ == '__main__':
        main('round-robin.conf', 'error.log')

def forward(socket_source, socket_destination):
    while True:
        data = socket_source.recv(4096)
        if data:
            socket_destination.sendall(data)
    # socket_source.shutdown(socket.SHUT_RD)
    # socket_destination.shutdown(socket.SHUT_WR)

while True:
    data,addr = socket_source.recvfrom(4096)
    if data and addr:
        socket_destination.sendto(data,addr)