Why is this code giving me error?

Question

I'm trying to build a tcp server and it keeps giving me this error, can you check out for me please?

########################################
import socket
import threading

server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

bind_ip = "0.0.0.0"
bind_port = 9999

server.bind((bind_ip, bind_port))

server.listen(5)

msg = "[*] Listening on: {0} {1}".format(bind_ip,bind_port)
print(msg)

def handle_client(client_socket):
request = client_socket.recv(1024)

msg1 = "[*] Received: ", request()
print(msg1)

client_socket.send("ACK!")
client_socket.close()

while True:
client, addr = server.accept()

msg2 = "[*] Accepted connection from: {0} {1}".format(addr[0],addr[1])
print(msg2)
client_handler = threading.Thread(target=handle_client,args=(client,))
client_handler.start()
####################################################

Answer 1

It still gives me this error:
##############################
[*] Listening on: 0.0.0.0 9999
Traceback (most recent call last):
File "C:\Users\mathe\Desktop\tcpserver.py", line 22, in <module>
client_socket.send("ACK!")
NameError: name 'client_socket' is not defined
####################################

Sorry for taking so long to reply to you, this website's UI is so disastrous it's awful to find where my threads are.