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✨MESSAGING APPLICATION✨

THis Application allow users to send and receive messages and images to other users.

Working Features

  • Creates an account for a client and allows him to login at any time.
  • Personal chat between two persons.
  • Group creation, Group chat and Admin Powers.
  • Image sharing
  • End to End Encryption
  • Load Balancing of servers

Tech

  • Python
  • Postgres
  • Socket Library
  • Threading
  • Bcrypt Library
  • pickle

Running

  • server side:
python3 load_server.py
python3 master_server.py
python3 server.py $PORT        # Run this as many terminals as you wish with a port number as an argument(Each time you run this a server is created)
  • client side:
python3 client.py

If there are no servers available, a message "Sorry, No services available" will be printed and the program is terminated else the client is binded to the server which is less busy.

For Login/#..

Program will ask for Login/#

  • For Login:

    Input: LOGIN
Input: Username
Input: Password

  • For #:

    Input: #
Input: Username
Input: Password

During # a .pem file is created that stores the private key of the user which is used for decrypting messages. During login we just load this key from that file. This has a demmerit that once a user # from a device, he has to login from that directory only all the times.

In case of successful login/#, the program will show the available clients and groups

For Personal Chat between two persons...

Program can send both text messages and images.

  • Login/#

  • To Enter personal chatroom

     Input: 1
 Input: username of person to whom you want to chat with

  • For text:

    Input: text 
Input: message

  • For Image:

    Input: image
Input: path to image

  • For leaving chat with that person

     Input: 0

  • To leave this chat room:

     Input: @#@EXIT@#@

If the receiver is offline then the message is stored in the database.

For Group Creation...

  • Login/#

  • To create a group

    Input: 2
Input: name of the group you want to create
Input: names of the participants

  • After you entered all the participants name

     Input: -1

A new group with given name and creator as the admin is created. This data is stored in database

For Group Chat...

  • Login/#

  • For entering a group chatroom

    Input: 3
Input: Name of the Group you want to chat with

  • For Chatting

    Input: 1
Input: type of image(text or image)
Input: 0 to stop messaging

  • For Adding a participant

    Input: 2
Output(if not an admin): Only admin can add/remove partipants
Input: Participant name

  • For Removing a participant

    Input: 3
Output(if not an admin): Only admin can add/remove partipants
Input: Participant name

  • For exiting chat with this group

    Input: 0

  • For leaving this chatroom

    Input: @#@EXIT@#@

Internal mechanism:

                                           client1 client2 client3  client4
                                              |      |        |       |
                                              |      |        |       |
                                               -----------------------
                                                          |
                                                     load_server
                                                          |
                                                          |
                                                  -----------------
                                                  |       |       |
                                               server1 server2 server3
                                                  |       |       |
                                                   \      |      /
                                                    \     |     /
                                                    master_server

Binding of clients and servers

  • First when we run the load_server.py, it will wait for the connections from clients
  • We also run the master_clients that will wait for servers
  • master_server is connected to all the servers that are currently working
  • Once a client.py is runned, the request is sent to load_server.py, Then it will check for the server which has least no. of clients
  • Then the client binds with that server
  • If a client is connected to a server, we will update this data in the database, From this info we will know how many clients a server is currently handling.
  • We also know which client is connected to which server from this table

Chatting

  • Consider client-A and client-B are connected to server-1. Then if A wants to send message to B the the encrypted message will go to server-1, server-1 sends this message to B, B will decrypt it and read
  • If A and B are connected to different servers, let A connected to server-1 and B to server-2. server-1 recieves message from A, since B is not connected to server-1, It will send this message to master_server. The master_server sends the message to server-2 to which B is connected. Then server-2 will send this message to B
  • If B is offline then the encrypted message is stored in the database. Once B comes online, he recieves the message through the server he connected from the database

Encryption

  • Used bcrypt for encrypting passwords and stored in database. We took a fixed salt. Since decrypting from encrypted password is not possible, any other person cannot know the password of client even though they have access of database.
  • Used rsa encryption for the messages and send the encrypted message to server. Only the sender and reciever(might be a person(personal message) or a set of people(group message)) will know what the message is.

Load Balancing

  • Distributed the clients among the servers equally using load_server so that the work load is equally balanced.
  • For the intercommunication between the servers we are running the master_server that acts as a intermediate in message transfer from a server to another server