Python3 网络通信 网络聊天室 文件传输

Python3 网络通信 网络聊天室 文件传输

功能描述

该项目将实现一个文字和文件传输的客户端和服务器程序通信应用程序。它将传输和接收视频文件。
文本消息必须通过TCP与服务器通信，而客户端自己用UDP传输视频文件。
程序将支持一下功能：

• 用户身份验证
• 向服务器发布消息
• 编辑或删除消息、读取消息
• 从服务器发送消息
• 读取活动用户的信息
• 上传视频文件从一个用户到另一个用户

简要流程

• 该项目将实现各种应用程序协议来实现以上功能。
• 服务器将监听指定为命令行参数的端口，并等待客户端监听连接。
• 客户端程序将发起一个与服务器的TCP连接。
• 在连接建立后，用户将启动身份验证过程。客户端将与用户交互通过命令行界面。
• 身份验证成功后，用户可以执行一系列命令
• 最终登出
• 客户端和服务器都必须打印有意义的提示消息

简要设计

• Server: 使用一个类来保存每个客户端信息，包括用户名和IP地址的映射，并多线程开始接收每个客户端的处理程序。
• Client: 三个线程:主线程为获取用户输入和发送到服务器，和一个线程为接收服务器响应，一个线程UDP传输文件

功能协议

• Login: flag(“Login”) + username + password
• MSG: flag(“MSG”) + message
• EDT: flag(“EDT”) + msg_index + msg_time + new_msg
• DLT: flag(“DLT”) + msg_index + msg_time
• RDM: flag(“RDM”) + msg_time
• ATU: flag(“ATU”)
• OUT: flag(“OUT”)
• UPD: flag(“UDP”) + username + filename

Usage

• Server： python server.py 端口号 最大密码尝试次数
• Client： python client.py 服务器IP 服务器端口 客户端UDP端口

效果展示

代码

import socket
import threading
import time
import sys
import os

UDP_port = 6666

LoginStatus = False
TCP_running = True

clientSocket = socket.socket()

login_Event = threading.Event()
response_Event = threading.Event()

user_list = []
USERNAME = ""

get IP address and port after ATU command
def get_address_port_by_username(name):
    if len(user_list) == 0:
        print("[error] need run ATU command first")
    else:
        for i in user_list:
            user_info = i.split(", ")
            username = user_info[0]
            address = user_info[1]
            port = user_info[2]
            if username == name:
                return address, port
    return None

LOGIN
def log_in(clientSocket,udp_port):
    global USERNAME
    print("Username: ", end="")
    name = input('')
    print("Password: ", end="")
    pwd = input('')

    FLAG = "LOGIN"
    USERNAME = name
    PWD = pwd

    login_msg = FLAG + "%%" + name + "%%" + PWD + "%%" + str(udp_port)
    clientSocket.send(login_msg.encode('utf-8'))

def reponse_to_client(recv_msg):
    global TCP_running
    global LoginStatus
    global login_Event
    send_msg = ""
    recv_msg_list = []
    recv_msg_list = recv_msg.split("%%")
    res = True
    if len(recv_msg_list) != 0:
        flag = recv_msg_list[0]

    if (flag == "LOGIN"):
        TYPE = recv_msg_list[1]
        if(TYPE == "0"):
            LoginStatus = True
        else:
            LoginStatus = False
        # inform the main loop the result from server
        login_Event.set()
        print(recv_msg_list[2])

    elif (flag == "MSG"):
        print(recv_msg_list[1])
    elif flag == "EDT":
        TYPE = recv_msg_list[1]
        if (TYPE == "0"):
            edit_res = True
        else:
            edit_res = False
        print(recv_msg_list[2])
    elif (flag == "RDM"):
        txt = recv_msg_list[1:]
        for i in txt:
            print(i)
        pass
    elif (flag == "DLT"):
        TYPE = recv_msg_list[1]
        if (TYPE == "0"):
            del_res = True
        else:
            del_res = False
        print(recv_msg_list[2])
        pass
    elif (flag == "ATU"):
        NUM = recv_msg_list[1]
        if NUM == "0":
            print(recv_msg_list[2])
        else:
            txt = recv_msg_list[2:]
            for i in txt:
                print(i)
                user_list.append(i)
    elif (flag == "OUT"):
        TCP_running = False
        print(recv_msg_list[1])

def read_server(s):
    global response_Event
    global TCP_running
    while TCP_running:
        # the thread always receive from server
        content = s.recv(2048).decode('utf-8')
        reponse_to_client(content)

        # inform the mian loop, resume it
        response_Event.set()
    # s.close()
    os._exit(1)

def execute_command(clientSocket):
    response_Event.clear()
    while TCP_running:
        print("Enter one of the following commands (MSG, DLT, EDT, RDM, ATU, OUT, UPD): ", end="")
        msg = input('')
        if not msg:
            continue
        command = msg.split(" ")[0]

        if command == "MSG":
            if len(msg.split(" ")) < 2:
                print("need arguments")
                continue

            txt = msg.split(" ")[1:]
            msg = command + "%%" + ' '.join(txt)
        elif command == "EDT":
            if len(msg.split(" ")) < 2:
                print("[error] need arguments")
                continue
            args = msg.split(" ")[1:]
            index = args[0][1:]
            dt = ' '.join(args[1:5])
            txt = ' '.join(args[5:])
            msg = command + "%%" + index + "%%" + dt + "%%" + txt

        elif command == "DLT":
            if len(msg.split(" ")) < 2:
                print("[error] need arguments")
                continue
            args = msg.split(" ")[1:]
            index = args[0][1:]
            dt = ' '.join(args[1:])
            msg = command + "%%" + index + "%%" + dt
            pass
        elif command == "RDM":
            if len(msg.split(" ")) < 2:
                print("[error] need arguments")
                continue

            dt = ' '.join(msg.split(" ")[1:])
            msg = command + "%%" + dt
        elif command == "ATU":
            if len(msg.split(" ")) < 2:
                pass
            else:
                print("[error] too many arguments")
                continue
            pass
        elif command == "OUT":
            if len(msg.split(" ")) < 2:
                pass
            else:
                print("[error] too many arguments")
                continue
            pass
        elif command == "UPD":
            if len(msg.split(" ")) < 3:
                print("[error] need more arguments")
                continue
            else:
                UDP_send(msg.split(" ")[1], msg.split(" ")[2])
                continue
        else:
            print("[error] unknown command")
            continue

        clientSocket.send(msg.encode('utf-8'))
        # block, waiting for server response
        time.sleep(0.3)
        response_Event.wait(30)
        response_Event.clear()

mian func
def tcp_start(server_IP, server_port, udp_port):
    global clientSocket
    clientSocket = socket.socket()
    clientSocket.connect((server_IP, server_port))

    TCP_t = threading.Thread(target=read_server, args=(clientSocket,)).start()

    # login
    while LoginStatus == False:
        log_in(clientSocket, udp_port)
        # waiting for server ...

        time.sleep(0.3)
        # block, waiting for server response
        login_Event.wait(30)
        login_Event.clear()
        if LoginStatus:
            # print("Debug: log in success")
            pass
        else:
            # print("Debug: log in fail")
            pass

    # commands
    execute_command(clientSocket)

def UDP_send(username, filename):
    global USERNAME
    address, port = get_address_port_by_username(username)
    BUF_SIZE = 1024
    # print(address, port)
    server_addr = (address, int(port))

    client = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    count = 0
    f = open(filename, 'rb')
    while True:
        if count == 0:
            # send the first message inculding filename
            data = "UDP%%"+USERNAME+"_"+filename
            client.sendto(data.encode('utf-8'), server_addr)

        data = f.read(BUF_SIZE)
        if str(data) != "b''":
            client.sendto(data, server_addr)
        else:
            client.sendto('end'.encode('utf-8'), server_addr)  # end for the file and send a speical "end" flag
            # lecture1.mp4 has been uploaded
            print(filename + " has been uploaded.")
            execute_command(clientSocket)
            break
        count += 1
        time.sleep(0.001)
    f.close()
    client.close()

def UDP_recv(udp_port):
    BUF_SIZE = 1024
    server_addr = ('127.0.0.1', udp_port)

    # UDP: socket.SOCK_DGRAM
    server = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    server.bind(server_addr)

    count = 0
    f = None
    filename = ""
    while True:
        data, addr = server.recvfrom(BUF_SIZE)
        if count == 0:
            # recive the starting message inculding filename
            recv_data_array = data.decode('utf-8').split("%%")
            if len(recv_data_array) > 1:
                if recv_data_array[0] == "UDP":
                    filename = recv_data_array[1]
                    f = open(filename, 'wb')
            count += 1
        elif str(data) != "b'end'":
            try:
                f.write(data)
                # print(count)
            except:
                print("[erroe] can not write")
            count += 1
        else:
            f.close()
            # print(count)
            count = 0
            print("\nReceived " + filename.split("_")[1] + " from " + filename.split("_")[0])

if __name__ == '__main__':
    # python client.py server_IP server_port client_udp_server_port
    if len(sys.argv) > 3:
        server_IP = sys.argv[1]
        server_port = int(sys.argv[2])
        client_udp_server_port = int(sys.argv[3])
        udp_recv_t = threading.Thread(target=UDP_recv, args=(client_udp_server_port,)).start()
        tcp_start(server_IP, server_port, client_udp_server_port)
    else:
        print("[error] Usage: python client.py server_IP server_port client_udp_server_port ")

    # just for test
    # server_IP = "127.0.0.1"
    # server_port = 9000
    # client_udp_server_port = 7777
    # udp_recv_t = threading.Thread(target=UDP_recv, args=(client_udp_server_port,)).start()
    # tcp_start(server_IP, server_port, client_udp_server_port)

Python 3
coding: utf-8

from socket import *
import time
import sys
import threading
import traceback

If true, print debug information
__DEBUG = False
max number of consecutive failed attempts
MAX_ERR_COUNT = 0
server IP
serverIP = '127.0.0.1'

record clients who try to connect to server
client_connect_list = []

ClientInfo class
manager client infomation
class ClientInfo():
    m_IP=""
    m_loginTimestamp = -1
    m_preLoginTime = -1
    m_username=""
    m_UDPServerPort = -1
    m_errorCount = 0

    def __init__(self, IP):
        self.m_IP = IP

    def add_logInfo(self, name, timestamp, UDPport):
        self.m_loginTimestamp = timestamp
        self.m_username = name
        self.m_UDPServerPort = UDPport

        if self.m_errorCount < MAX_ERR_COUNT:
            self.m_preLoginTime = self.m_loginTimestamp
            # print("Debug: self.m_errorCount: " + str(self.m_errorCount))
            return True
        else:
            if (int(self.m_loginTimestamp) - int(self.m_preLoginTime) > 30):
                self.m_errorCount = 0
                self.m_errorCount = self.m_errorCount + 1
                return True
            else:
                return False
    # record number_of_consecutive_failed_attempts
    def error_password(self):
        self.m_errorCount = self.m_errorCount + 1

check name and password
def check_credential(username, password):
    res = False
    with open('credentials.txt', 'r') as file:
        credential_list = file.readlines()
        for credential in credential_list:
            name = credential.strip().split(" ")[0]
            pwd = credential.strip().split(" ")[1]
            if (name==username and pwd == password):
                res = True
                break
    if __DEBUG: print("check_credential: res: " , res)
    return  res

Get client infomation by IP
def get_client_from_connect_list(IP):
    for c in client_connect_list:
        if c.m_IP == IP:
            return c
    return None

Add a new client to cse_userlog.txt
def add_user_log(name, timestamp, IP, UDPport):
    dt = time.strftime("%d %b %Y %H:%M:%S", time.localtime(int(timestamp)))
    address = IP[0]
    txt = dt + "; " + name + "; " + address + "; " + str(UDPport)
    index = 0
    # read old file to get log index
    with open('cse_userlog.txt', mode='r', encoding="utf-8") as user_file:
        log_list = user_file.readlines()
        if log_list:
            last_line = log_list[-1]
            index = int(last_line.strip().split("; ")[0])
        else:
            index = 0
    # write new log in file
    with open('cse_userlog.txt', mode='a+', encoding="utf-8") as user_file:
        msg = str(index+1) + '; ' + txt
        user_file.write(msg + "\n")

OUT: delete a client from cse_userlog.txt and adjust other client's index
def del_user_log(name):
    new_log_list=[]
    index = 1
    with open('cse_userlog.txt', mode='r', encoding="utf-8") as user_file:
        log_list = user_file.readlines()
        for log in log_list:
            log_arr = log.split("; ")
            log_txt = log_arr[1:]
            log_prot = log_arr[4]
            log_addr = log_arr[3]
            log_name = log_arr[2]
            if log_name == name:
                if __DEBUG: print("Debug: find same IP need to delete: " + str(log_arr[0]))
                pass
            else:
                txt = "; ".join(i for i in log_txt)
                msg = str(index) + "; " + txt
                index = index + 1
                new_log_list.append(msg)

    with open('cse_userlog.txt', mode='w', encoding="utf-8") as user_file:
        user_file.writelines(new_log_list)

ATU: read other user log from cse_userlog.txt and return
def show_user_log_exclude_self(name):
    new_log_list=[]

    with open('cse_userlog.txt', mode='r', encoding="utf-8") as user_file:
        log_list = user_file.readlines()
        for log in log_list:
            log_arr = log.split("; ")
            log_txt = log_arr[1:]
            log_name = log_arr[2]
            if log_name == name :
                if __DEBUG: print("Debug: find same name no need to show: " + str(log_arr[0]))
                pass
            else:
                txt = "; ".join(i for i in log_txt)
                msg = txt
                new_log_list.append(msg)
    return  new_log_list

MSG: When someone posts a new message, add it to the messagelog.txt
def add_msg_log(name, timestamp, txt):
    dt = time.strftime("%d %b %Y %H:%M:%S", time.localtime(int(timestamp)))
    log_txt = dt + "; " + name + "; " + txt
    index = 0
    with open('messagelog.txt', mode='r', encoding="utf-8") as msg_file:
        log_list = msg_file.readlines()
        if log_list:
            last_line = log_list[-1]
            index = int(last_line.strip().split("; ")[0])
        else:
            index = 0
    with open('messagelog.txt', mode='a+', encoding="utf-8") as msg_file:
        msg = str(index + 1) + '; ' + log_txt + '; ' + 'no'
        msg_file.write(msg + "\n")
    return index + 1

convert formatted date time to timestamp
def dt_to_timestamp(dt):
    timeArray = time.strptime(dt, "%d %b %Y %H:%M:%S")
    timeStamp = int(time.mktime(timeArray))
    return timeStamp

RDM: read message log by different time
def read_msg_log(timestamp):
    new_log_list=[]
    with open('messagelog.txt', mode='r', encoding="utf-8") as msg_file:
        log_list = msg_file.readlines()
        for log in log_list:
            log_arr = log.split("; ")
            log_dt = log_arr[1]
            log_timestamp = dt_to_timestamp(log_dt)
            log_name = log_arr[2]
            if log_timestamp < timestamp:
                pass
            else:
                new_log_list.append(log)
    return new_log_list

DLT: delete a client's own message by time
def del_msg_log(name, del_index, del_dt):
    del_res = False
    del_txt = ""
    new_log_list=[]
    index = 1
    with open('messagelog.txt', mode='r', encoding="utf-8") as msg_file:
        log_list = msg_file.readlines()
        for log in log_list:
            log_arr = log.split("; ")
            log_txt = log_arr[1:]
            log_dt = log_arr[1]
            log_name = log_arr[2]
            if log_dt == del_dt and log_name == name and index == del_index:
                del_res = True
                del_txt = log_arr[3]
                if __DEBUG: print("Debug: find same name and index and time need to delete: " + str(log_arr[0]))
                pass
            else:
                txt = "; ".join(i for i in log_txt)
                msg = str(index) + "; " + txt
                index = index + 1
                new_log_list.append(msg)

    with open('messagelog.txt', mode='w', encoding="utf-8") as msg_file:
        msg_file.writelines(new_log_list)

    return del_res, del_txt

EDT: edit a client's own message by time
def edit_msg_log(name, edit_index, edit_dt, edit_txt):
    edit_res = False
    new_log_list=[]
    edit_time = ''
    with open('messagelog.txt', mode='r', encoding="utf-8") as msg_file:
        log_list = msg_file.readlines()
        for log in log_list:
            log_arr = log.split("; ")
            log_index = log_arr[0]
            log_txt = log_arr[3]
            log_dt = log_arr[1]
            log_name = log_arr[2]
            if log_dt == edit_dt and log_name == name and log_index == str(edit_index):
                edit_res = True
                edit_time = time.strftime("%d %b %Y %H:%M:%S", time.localtime(int(time.time())))
                log_arr[3] = edit_txt
                log_arr[1] = edit_time
                log_arr[4] = "yes\n"
                if __DEBUG: print("Debug: find same name and index and time need to edit: " + str(log_arr[0]))
                log = "; ".join(log_arr)
                new_log_list.append(log)
                if __DEBUG: print("Debug: new log ", log)
            else:
                new_log_list.append(log)

    with open('messagelog.txt', mode='w', encoding="utf-8") as msg_file:
        msg_file.writelines(new_log_list)

    return edit_res, edit_time

parse the msg from client and make different responses based on different client commands
def reponse_to_client(clientSocket, IP, recv_msg):
    socket_status = True
    send_msg = ""
    recv_msg_list = []
    recv_msg_list = recv_msg.split("%%")
    pwd_status = True
    if len(recv_msg_list) != 0:
        flag = recv_msg_list[0]
    else:
        print("[error] parse error")
        pass

    if __DEBUG: print("Debug: flag is " + flag)
    client = get_client_from_connect_list(IP)
    # response to login
    if (flag == "LOGIN"):
        name = recv_msg_list[1]
        pwd = recv_msg_list[2]
        UDPPort = recv_msg_list[3]
        pwd_status = check_credential(name, pwd)
        # if wrong name and password, number of consecutive failed attempts adds 1
        if not pwd_status:
            client.error_password()

        if client is None:
            client = ClientInfo(IP)
            client_connect_list.append(client)
        # save user information
        add_status = client.add_logInfo(name, time.time(), UDPPort)
        if add_status == True:
            if pwd_status == False:
                TYPE = "1"
                if client.m_errorCount == MAX_ERR_COUNT:
                    DATA = "Invalid Password. Your account has been blocked. Please try again later"
                else:
                    DATA = "Invalid Password. Please try again!"
            elif pwd_status == True:
                TYPE = "0"
                DATA = "Log in sucessfully!"
                add_user_log(name, client.m_loginTimestamp, IP, client.m_UDPServerPort)
                server_output = client.m_username + " log in sucessfully"
                print(server_output)
        else:
            TYPE = "2"
            DATA = "Your account is blocked due to multiple login failures. Please try again later"
        FLAG = flag
        send_msg = FLAG + "%%" + TYPE + "%%" + DATA

    # response to "MSG" command
    elif (flag == "MSG"):
        txt = recv_msg_list[1]
        if __DEBUG: print("Debug: " + txt)
        timestamp = time.time()
        msg_index = add_msg_log(client.m_username, timestamp, txt)
        dt = time.strftime("%d %b %Y %H:%M:%S", time.localtime(int(timestamp)))
        FLAG = flag
        DATA = "Message #" + str(msg_index) + " posted at " + dt
        send_msg = FLAG + "%%" +  DATA
        server_output = client.m_username + " posted MSG #" + str(msg_index) + " \"" + txt + "\" at " + dt + "."
        print(server_output)

    # response to "RDM" command
    elif (flag == "RDM"):
        FLAG = flag
        DATA = ""
        dt = recv_msg_list[1]
        try:
            timestamp = dt_to_timestamp(dt)
        except Exception as e:
            print(e)
            send_msg = FLAG + "%%" + "unknown time, please check time format"
            clientSocket.send(send_msg.encode('utf-8'))
            return
        log_list = read_msg_log(timestamp)
        if len(log_list) == 0:
            DATA = "no new message"
        else:
            # print(log_list)
            for log in log_list:
                log_arr = log.split("; ")
                log_edit_status = log_arr[4]
                log_index = log_arr[0]
                log_name = log_arr[2]
                log_txt = log_arr[3]
                log_dt = log_arr[1]
                if log_edit_status.strip() == "no":
                    log_edit_status = "posted"
                elif log_edit_status.strip() == "yes":
                    log_edit_status = "edited"
                m = "#" + log_index + " " + log_name + ", " + log_txt + ", " + log_edit_status + " at " + log_dt + "%%"
                DATA = DATA + m
        send_msg = FLAG + "%%" + DATA
        #Yoda issued RDM command
        server_output = client.m_username + " issued RDM command."
        print(server_output)

    # response to "EDT" command
    elif (flag == "EDT"):
        FLAG = flag
        edit_index = int(recv_msg_list[1])
        edit_dt = recv_msg_list[2]
        edit_txt = recv_msg_list[3]
        edit_res, edit_time = edit_msg_log(client.m_username, edit_index, edit_dt, edit_txt)

        if edit_res:
            TYPE = "0"  # del success
            DATA = "Message #" + str(edit_index) + " edited at " + edit_time + "."
            server_output = client.m_username + " edited MSG #" + str(edit_index) + " \"" + edit_txt + "\" at " + edit_time + "."
            print(server_output)
        else:
            TYPE = "1"  # del fail
            DATA = "Edit message fail, can not find such message"
            server_output = client.m_username + " " + DATA
            print(server_output)
        send_msg = FLAG + "%%" + TYPE + "%%" + DATA

        pass

    # response to "DLT" command
    elif (flag == "DLT"):
        FLAG = flag
        del_index = int(recv_msg_list[1])
        del_dt = recv_msg_list[2]
        del_res, del_txt = del_msg_log(client.m_username, del_index, del_dt)
        del_time = time.strftime("%d %b %Y %H:%M:%S", time.localtime(int(time.time())))
        if del_res:
            TYPE = "0"  # del success
            DATA = "Message #" + str(del_index) + " deleted at " + del_time + "."
            server_output = client.m_username + " deleted MSG #" + str(
                del_index) + " \"" + del_txt + "\" at " + del_time + "."
            print(server_output)
        else:
            TYPE = "1"  # del fail
            DATA = "Delete message fail, can not find such message"
            server_output = client.m_username + " " + DATA
            print(server_output)

        send_msg = FLAG + "%%" + TYPE + "%%" + DATA

    # response to "ATU" command
    elif (flag == "ATU"):
        FLAG = flag
        DATA = ""
        user_list = show_user_log_exclude_self(client.m_username)
        NUM = len(user_list)
        if len(user_list) == 0:
            DATA = "no other active user"
        else:
            for user in user_list:
                user_arr = user.split("; ")
                user_dt = user_arr[0]
                user_name = user_arr[1]
                user_address = user_arr[2]
                user_port = user_arr[3]
                txt = user_name + ", " + user_address + ", " + user_port.strip() + ", active since " + user_dt + "."
                DATA = DATA + txt + '%%'
        send_msg = FLAG + "%%" + str(NUM) + "%%" + DATA
        server_output = client.m_username + " issued ATU command."
        print(server_output)

    # response to "OUT" command
    elif (flag == "OUT"):
        del_user_log(client.m_username)
        client = get_client_from_connect_list(IP)
        FLAG = flag
        send_msg = FLAG + "%%" + "Bye, " + client.m_username + "!"
        socket_status = False
        server_output = client.m_username + " logout"
        print(server_output)

    if send_msg != "":
        clientSocket.send(send_msg.encode('utf-8'))

    if not socket_status:
        clientSocket.close()

Try to recvice msg from client
def read_client(socket, IP):
    try:
        return socket.recv(2048).decode('utf-8')
    except:
        # if exception, indicating that the connection failed, the client is deleted
        print(str(IP) + ' Left!')

Always wait for a message from the client
def recv_handler(socket, clientAddress):
    try:
        while True:
            content = read_client(socket, clientAddress)
            if content is None:
                break
            else:
                if __DEBUG: print(str(clientAddress) + " received: " + content)

                reponse_to_client(socket, clientAddress, content)

    except Exception as e:
        # raise Exception
        print("[error]: ", e)
        exstr = traceback.format_exc()
        if __DEBUG: print("debug: " + exstr)
        pass

def start(server_port):
    serverSocket = socket(AF_INET, SOCK_STREAM)
    serverSocket.bind((serverIP, server_port))
    serverSocket.listen(1)
    print("Server start ... ")
    print("waiting client ...")
    while True:
        clientSocket, clientAddress = serverSocket.accept()

        # record each client when server accept successfully
        client = ClientInfo(clientAddress)
        client_connect_list.append(client)
        if __DEBUG: print(str(clientAddress) + ' is trying to connect!')

        # start recv_handler for each client
        threading.Thread(target=recv_handler, args=(clientSocket, clientAddress)).start()

if __name__ == '__main__':
    # create messagelog.txt
    msg_file = open('messagelog.txt', 'w')
    msg_file.close()
    # create cse_userlog.txt
    user_file = open('cse_userlog.txt', 'w')
    user_file.close()

    # python server.py server_port number_of_consecutive_failed_attempts
    if len(sys.argv) > 2:
        server_port = int(sys.argv[1])
        MAX_ERR_COUNT = int(sys.argv[2])
        start(server_port)
    else:
        print("[error] Usage: python server.py server_port number_of_consecutive_failed_attempts ")

    # just for test
    # server_port = 9000
    # MAX_ERR_COUNT = 6
    # start(server_port)

Original: https://www.cnblogs.com/HsinTsao/p/15406909.html
Author: HsinTsao
Title: Python3 网络通信 网络聊天室 文件传输