✨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