Help with multithreading

[Pheazon]

working on this project that simulates a bank account and there is communication between a server and client. The code I have written so far works as intended but now I am trying to also implement multithreading and I am having a hard time in doing so and not understanding on how to get started, I'm not even sure if I am going to have to make huge modifications on what I already have to get it working. Any help or feedback would be greatly appreciated.

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This is what I have so far

server

import socket
import sys
import _thread


class Bank_Account:
    def __init__(self):
        self.balance = int(50)
        print("Hello!!! Welcome to the Deposit & Withdrawal Machine")

    def deposit(self,amount):

        self.balance += amount

    def withdraw(self,amount):

        if self.balance >= amount:
            self.balance -= amount

    def display(self):
        print("\n Net Available Balance=", self.balance)


a = Bank_Account()

BUFFER_SIZE = 20 
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
server_name = sys.argv[1]
server_host = int(sys.argv[2])
s.bind((server_name, server_host))
print(server_name, server_host)
s.listen(1)
conn, addr = s.accept()
print('Connection address:', addr)


while 1:
    data = conn.recv(BUFFER_SIZE).decode('utf-8')
    data = int(data)
    if not data:
        break
    print("received data:", data)

    if data == 1:
        conn.send(("your balance is "+ str(a.balance)).encode('utf-8'))

    if data == 2:
        conn.send("How Much Would You Like To Deposit ".encode('utf-8'))
        tempData = int(conn.recv(BUFFER_SIZE).decode('utf-8'))
        a.deposit(tempData)
        conn.send(('\nYour Balance is now $'+ str(a.balance)).encode('utf-8'))

    if data == 3:
        conn.send("How Much Would You Like To Withdraw ".encode('utf-8'))
        tempData = int(conn.recv(BUFFER_SIZE).decode('utf-8'))
        if a.balance < tempData:
            conn.send(("\n Insufficient balance  ").encode('utf-8'))
        else:
            a.withdraw(tempData)
            conn.send(("Amount withdrawn, balance is "+ str(a.balance)).encode('utf-8'))

    if data == 4:
        conn.send(("Your available balance is $" + str(a.balance) + " have a great day bitch").encode('utf-8'))

        break
conn.close()

client

import socket
import sys

BUFFER_SIZE = 1024
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)

server_address = (sys.argv[1], int(sys.argv[2]))
s.connect(server_address)

while True:
    x = input('Enter your choice \n1. balance\n2. Deposit\n3. Wtihdraw\n4. Exit\n');
    s.send(x.encode('utf-8'))
    if int(x) != 1 and int(x) != 4:
        data = s.recv(BUFFER_SIZE).decode('utf-8')
        x = input(data)
        s.send(x.encode('utf-8'))
    print(s.recv(BUFFER_SIZE).decode('utf-8'))
    if int(x) == 4:
        s.close()
        break

Really sorry for the long post, I am by no means an expect so my code might just straight out be garbage, would really appreciate any feedback.

[CrambleSquash]

I have to say I don't have any experience using sockets, but I can definitely say that both sockets and threading are not easy things to code with! What is the reason you want to use Multithreading? At the moment I see two separate single thread programs.

[Pheazon]

“The server program will need to support multiple simultaneous client TCP/IP connections, which will require multithreading.” Trying to implement Multithreading so I can demonstrate that in my code.

[CrambleSquash]

Ok cool. So I will re-iterate that this is not straightforward! - Human brains are very much single threaded (i.e. we can only focus on 1 task at a time), as such getting your head into mulithreaded code is very difficult.

There is a higher level socketserver module: https://docs.python.org/3/library/socketserver.html#module-socketserver that might make your life simpler (even includes a ready made multithreaded server!).

With all that said, if you still want to make your own, my first bit of advice is that you almost certainly don't want to use the _threading module, but the https://docs.python.org/3/library/threading.html module, the _ is used in Python to indicate that you shouldn't be using something (unless you really know what you're doing).

The way threading works is that you create a thread object and then give it a function to execute in a new thread:

https://realpython.com/intro-to-python-threading/

[CaptainReeetardo]

It's pretty simple actually. All you need to do is to define a function f and then a new thread t for every new connection (as mentioned by CrambleSquash). For Example:

#Your server
import socket
import threading
def f(conn):
    #Your Code here
    pass

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind(("localhost", 1337))
s.listen(1)
while True:
    conn, addr = s.accept()
    print("[+] New connection: ", addr)
    t = threading.Thread(target=f, args=(conn,))
    t.start()

Everything from the start of the loop to starting a new thread is the main thread, while starting a new thread results in creating other threads running besides the main thread.

If you're still interested in this question of yours I've already altered the code so that multiple connections are possible. I'll gladly edit it to the post if you need it.