Client.py

import socket
import select
import errno
import sys

HEADER_LENGTH = 10
Host = "127.0.0.1"
Port = 8080

my_username = input("Username: ")
client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
#socket.socket([family], [type] , [proto] )
# AF_INET:Server與Server間的串接
# SOCK_STREAM:用TCP方式
client_socket.connect((Host, Port))
client_socket.setblocking(False)
# 取消socket的阻塞狀態
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: {}'.format(str(e)))
            sys.exit()
        continue

    except Exception as e:
        print('Reading error: {}'.format(str(e)))
        sys.exit()