README.md

assignment report

I use python 3.7.9 for this assignment

Data structure design

credential

there is a file called credential.txt, which is used for Authentication

the struct is

username1 password1

username2 password2

user data

there is a file called userData.json

it records the offline message, blacklist, start time, end time and it's IP and port number

Every we set up a new server ,userData.json file will be renewed

the struct is

    "username": {
        "message": ["", ""],
        "blackList": ["", ""],
        "active_period": [
            {
                "start":
                "end":
            }
        ],
        "clientAddress": [IP, port]
    }

program design

server

The server will record

• users be blocked
• online user
• client threads
• port been used

The server can

• Authentication
• Message
• Notifications
• Find users online
• Find online history
• show Blacklist to client

client

client is responsible to receive data from server and communicate with user

Client have two thread

• input thread

​ this thread keeps listening to the user's input,

​ when the thread receive a input, it will respond to server or to a p2p-connection client

• receive thread

​ this thread keeps listening to the server

each p2p connection is connected, then there will have one more thread which keeps listening to the p2p-connection client

how system works

• set up server

• set up client

  • input user name

  • input the password

  you can have multiple user

• when you want to create a p2p connection, remember to input the yes or no

the other system design is similar to the assignment specification

errors

• in the credentials.txt there may have some test user name and password, delete it before test
• logout broadcast in private not finish
• sometime there will have some json error, it happens rarely(I don't know it still exists or not)

Application Layer Protocol

messages the clients and server exchange

• server

  • sending:
    • by clientsocket.send()
    • it will auto reply to the client's message
  • receiving:
    • by clientsocket.recv(1024)
    • it will split the receiver's data by <space>, it will keep tracking the first keyword, and do the corresponding reply

• client

  • sending:

  • • by clientsocket.send()

    • it will send message corresponding to user input to the server

    • it will read the input from user and auto communication with server

  • receiving:

    • by clientsocket.recv(1024)
    • receive user input
    • receive server reply

actions

setup

1. the server keeps accepting new client, create a new thread when a new client connected,

   and the server will auto reply to clients

2. Then the server will do Authentication with client

3. Then client will create two thread for receiving message from server and for receiving input from the user

   • the thread listen to user will detect Peer to peer Messaging(private()) and stopprivate()
   • the thread listen to server will detect startprivate()

4. the client will ask the server for the offline message

5. the client will tell server to broadcast the presence

6. message exchanging start

private

the square is client1 who want to start a p2p connection with triangle (client 2)

the circle is server

When the triangle receive [request], a global variable privateMessage will be changed in ReceiveServer(Thread), it will tell InputThread(Thread) to receive a yes/no