client.py

import socket
import select
import errno
import sys

HEADER_LENGTH = 10
IP = "127.0.0.1"
PORT = 1234

my_username = input("Username: ")

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

client_socket.connect((IP, PORT))
client_socket.setblocking(False)

username = my_username.encode("utf-8")
username_header = f"{len(username):<{HEADER_LENGTH}}".encode("utf-8")
client_socket.send(username_header + username)

while True:
    message = input(f"{my_username} > ")
    if message:
        message = message.encode("utf-8")
        message_header = f"{len(message) :< {HEADER_LENGTH}}".encode("utf-8")
        client_socket.send(message_header + message)
    try:
        while True:
            username_header = client_socket.recv(HEADER_LENGTH)
            if not len(username_header):
                print("Connection closed by the server")
                sys.exit()
            username_length = int(username_header.decode("utf-8").strip())
            username = client_socket.recv(username_length).decode("utf-8")

            message_header = client_socket.recv(HEADER_LENGTH)
            message_length = int(message_header.decode("utf-8").strip())
            message = client_socket.recv(message_length).decode("utf-8")

            print(f"{username} > {message}")
    except IOError as e:
        if e.errno != errno.EAGAIN and e.errno != errno.EWOULDBLOCK:
            print("reading error", str(e))
            sys.exit()
        continue
    except Exception as e:
        print('General error', str(e))