问使用echo客户端/服务器测试的NameError :客户端无法向服务器发送自定义消息

EN

import socket

HOST = ''
PORT = 4040

def create_listen_socket(host, port):
    """ Setup the sockets our server will receive connection
    requests on """
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    sock.bind((host, port))
    sock.listen(100)
    return sock

def recv_msg(sock):
    """ Wait for data to arrive on the socket, then parse into
    messages using b'\0' as message delimiter """
    data = bytearray()
    msg = ''
    # Repeatedly read 4096 bytes off the socket, storing the bytes
    # in data until we see a delimiter
    while not msg:
        recvd = sock.recv(4096)
        if not recvd:
            # Socket has been closed prematurely
            raise ConnectionError()
        data = data + recvd
        if b'\0' in recvd:
            # we know from our protocol rules that we only send
            # one message per connection, so b'\0' will always be
            # the last character
            msg = data.rstrip(b'\0')
    msg = msg.decode('utf-8')
    return msg

def prep_msg(msg):
    """ Prepare a string to be sent as a message """
    msg += '\0'
    return msg.encode('utf-8')

def send_msg(sock, msg):
    """ Send a string over a socket, preparing it first """
    data = prep_msg(msg)
    sock.sendall(data)

import tincanchat

HOST = tincanchat.HOST
PORT = tincanchat.PORT

def handle_client(sock, addr):
    """ Receive data from the client via sock and echo it back """
    try:
        msg = tincanchat.recv_msg(sock) # Blocks until received
                                    # complete message
        print('{}: {}'.format(addr, msg))
        tincanchat.send_msg(sock, msg) # Blocks until sent
    except (ConnectionError, BrokenPipeError):
        print('Socket error')
    finally:
        print('Closed connection to {}'.format(addr))
        sock.close()

if __name__ == '__main__':
    listen_sock = tincanchat.create_listen_socket(HOST, PORT)
    addr = listen_sock.getsockname()
    print('Listening on {}'.format(addr))

    while True:
        client_sock, addr = listen_sock.accept()
        print('Connection from {}'.format(addr))
        handle_client(client_sock, addr)

import sys, socket
import tincanchat

HOST = sys.argv[-1] if len(sys.argv) > 1 else '127.0.0.1'
PORT = tincanchat.PORT

if __name__ == '__main__':
    while True:
        try:
            sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
            sock.connect((HOST, PORT))
            print('\nConnected to {}:{}'.format(HOST, PORT))
            print("Type message, enter to send, 'q' to quit")
            msg = input()
            if msg == 'q': break
            tincanchat.send_msg(sock, msg) # Blocks until sent
            print('Sent message: {}'.format(msg))
            msg = tincanchat.recv_msg(sock) # Block until
                                        # received complete
                                        # message
            print('Received echo: ' + msg)
        except ConnectionError:
            print('Socket error')
            break
        finally:
            sock.close()
            print('Closed connection to server\n')

Connected to 127.0.0.1:4040
Type message, enter to send, 'q' to quit
Hello
Closed connection to server

Traceback (most recent call last):
  File "C:\xxxxxxxxx\1.2-echo_client-uni.py", line 22, in         <module>
    except ConnectionError:
NameError: name 'ConnectionError' is not defined