[Python] How do I achieve Python TCP Socket Client/Server with Communications Encrypted?

Backstory: what I have done

{Codes at the bottom} I've already coded the multithreaded client and server programs using python socket, with the help of the following sites:

I. Echo Client and Server

II. Socket Server with Multiple Clients | Multithreading | Python

III. Python Socket Receive Large Amount of Data
​

Regarding Encryption & Decryption

(1) Exactly at what places in my codes should I encrypt/decrypt my message? Do I encrypt the messages themselves after the user inputs or do I encrypt the byte streams after the input messages have been encoded?

(2) And how am I supposed to encrypt/decrypt the communication properly and efficiently? (It'd be nice to see code solutions with explanation, many thanks)
​

My Codes Currently


_server.py

import socket
import os
from _thread import *
import struct # Here to convert Python data types into byte streams (in string) and back

# ---- To Avoid Message Boundary Problem on top of TCP protocol ----
def send_msg(sock: socket, msg): # ---- Use this to send
# Prefix each message with a 4-byte length (network byte order)
msg = struct.pack('>I', len(msg)) + msg
sock.sendall(msg)

def recv_msg(sock: socket): # ---- Use this to receive
# Read message length and unpack it into an integer
raw_msglen = recvall(sock, 4)
if not raw_msglen:
return None
msglen = struct.unpack('>I', raw_msglen)[0]
# Read the message data
return recvall(sock, msglen)

def recvall(sock: socket, n: int):
# Helper function to receive n bytes or return None if EOF is hit
data = bytearray()
while len(data) < n:
packet = sock.recv(n - len(data))
if not packet:
return None
data.extend(packet)
return data

# ---- Server Communication Setup

HOST = '127.0.0.1' # Standard loopback interface address (localhost)
PORT = 65432 # Port to listen on (non-privileged ports are > 1023)
ThreadCount = 0

try: # create socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print ("Socket successfully created")
except socket.error as err:
print ("socket creation failed with error %s" %(err))

try: # bind socket to an address
s.bind((HOST, PORT))
except socket.error as e:
print(str(e))

print('Waitiing for a Connection..')
s.listen(3)

def threaded_client(conn: socket):
conn.send(str.encode('Welcome to the Server'))
while True:
# data = conn.recv(2048) # receive message from client
data = recv_msg(conn)
reply = 'Server Says: ' + data.decode('utf-8')
if not data:
break
# conn.sendall(str.encode(reply))
send_msg(conn, str.encode(reply))
conn.close()

while True:
Client, addr = s.accept()
print('Connected to: ' + addr[0] + ':' + str(addr[1]))
start_new_thread(threaded_client, (Client, )) # Calling threaded_client() on a new thread
ThreadCount += 1
print('Thread Number: ' + str(ThreadCount))
s.close()


_client.py

import socket
import struct # Here to convert Python data types into byte streams (in string) and back

# ---- To Avoid Message Boundary Problem on top of TCP protocol ----
def send_msg(sock: socket, msg): # ---- Use this to send
# Prefix each message with a 4-byte length (network byte order)
msg = struct.pack('>I', len(msg)) + msg
sock.sendall(msg)

def recv_msg(sock: socket): # ---- Use this to receive
# Read message length and unpack it into an integer
raw_msglen = recvall(sock, 4)
if not raw_msglen:
return None
msglen = struct.unpack('>I', raw_msglen)[0]
# Read the message data
return recvall(sock, msglen)

def recvall(sock: socket, n: int):
# Helper function to receive n bytes or return None if EOF is hit
data = bytearray()
while len(data) < n:
packet = sock.recv(n - len(data))
if not packet:
return None
data.extend(packet)
return data

# ---- Client Communication Setup ----

HOST = '127.0.0.1' # The server's hostname or IP address
PORT = 65432 # The port used by the server

try:
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print ("Socket successfully created")
except socket.error as err:
print ("socket creation failed with error %s" %(err))

print('Waiting for connection')
try:
s.connect((HOST, PORT))
except socket.error as e:
print(str(e))

Response = s.recv(1024)
while True:
Input = input('Say Something: ')
# s.send(str.encode(Input))
send_msg(s, str.encode(Input))
# Response = s.recv(1024)
Response = recv_msg(s)
print(Response.decode('utf-8'))

s.close()

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