Decentralized Chat System using Mnesia DBMS

This is a Distributed and decentralized Peer-to-Peer(P2P) group chat system using Mnesia (a distributed telecommunications DBMS)that supports exchanges of text messages between multiple group(not individual) along with basic functionalities

Instructions

To run the code, compile the files chat_client, chat_server, chat_supervisor & db_logic respectively.

To start the chat service, start erlang with a name and set cookies, and run chat_client:start_link():

> erl -sname alice -cookies 1234

(alice@DESKTOP-BCH0NID)1> chat_client:start_link().

{local,chat_supervisor} (<0.86.0>) starting... 
{local,chat_server} (<0.87.0>) starting...     
true

To connect another peer, start erlang with a name, and the same cookie, and run chat_client:addNode(Host), where Host is any running peer (note this gives an error {aborted,{already_exists,schema,'bob@DESKTOP-BCH0NID'}}, but running mnesia:info() confirms all is as should be):

> erl -sname bob -cookies 1234

(bob@DESKTOP-BCH0NID)1> chat_client:addNode('alice@DESKTOP-BCH0NID').

{local,chat_supervisor} (<0.103.0>) starting... 
{local,chat_server} (<0.104.0>) starting...
[{aborted,{already_exists,schema,'bob@DESKTOP-BCH0NID'}}]

From any running peer you can interact with the service via the following functions in chat_client:

• addNode/1: Add local node to the cluster if the chat has been started. i.e. this is not called from the node that initialises the chat-service. (Host must be a running peer)
• createGroup/1: Creates a new group with the given name
• groupList/0 : Show all available group(s) as a list
• sendMessage/2: Sends a message to the given group
• findUser/2: Checks whether the user, User exists in the given group
• findGroup/1: Checks whether the group, Group exists
• listUsers/1: Lists all users in the given group
• viewHistory/1: Lists the chat history for the given group

Examples

(After compiling as described)

Starting the chat and connecting another peer

shell 1

> erl -sname alice -cookies 1234

(alice@DESKTOP-BCH0NID)1> chat_client:start_link().

{local,chat_supervisor} starting... 
{local,chat_server} starting...     
true

shell 2

> erl -sname bob -cookies 1234

(bob@DESKTOP-BCH0NID)1> chat_client:addNode('alice@DESKTOP-BCH0NID').

{local,chat_supervisor} starting... 
{local,chat_server} starting...
[{aborted,{already_exists,schema,'bob@DESKTOP-BCH0NID'}}]

Creating a group

(alice@DESKTOP-BCH0NID)2> chat_client:createGroup(birds). 
The group birds has been created.
ok

Seeing the List of chat group(s)

This function is useful if the user forgets the group name or to see other group available as open chat channels

(alice@DESKTOP-BCH0NID)10> chat_client:groupList().
---List of available groups--- 
 [birds,dinosaurs,mammals]
ok

Sending a message to a group

Sending a message will result in the chat-history being shown to any peers, which have sent a message to the given group.

shell 1

(alice@DESKTOP-BCH0NID)3> chat_client:sendMessage(birds, "Hello from Alice, the 
parrot :)").
You have sent your message to all users in group named 'birds'. 
 Users: ['alice@DESKTOP-BCH0NID']
---Chat history of group named 'birds'---
---START---
'Alice': 
 "Hello from Alice, the parrot :)" -- ['2021-05-22 12:17:02']

---END OF CHAT HISTORY--
ok

shell 2

(bob@DESKTOP-BCH0NID)3> chat_client:sendMessage(birds, "Hello, Alice. Welcome to the group!").
You have sent your message to all users in group named 'birds'. 
 Users: ['bob@DESKTOP-BCH0NID','alice@DESKTOP-BCH0NID']
---Chat history of group named 'birds'---
---START---
'Alice': 
 "Hello from Alice, the parrot :)" -- ['2021-05-22 12:17:02']

'Bob': 
 "Hello, Alice. Welcome to the group!" -- ['2021-05-22 12:20:06']

---Chat history of group named 'birds'---
---START---
---END OF CHAT HISTORY--
ok

The message sent from bob, will result in the chat-history being shown to alice:

(alice@DESKTOP-BCH0NID)5> 'Alice':
 "Hello from Alice, the parrot :)" -- ['2021-05-22 12:17:02']

(alice@DESKTOP-BCH0NID)5> 'Bob':
 "Hello, Alice. Welcome to the group!" -- ['2021-05-22 12:20:06']

Searching for a user

(alice@DESKTOP-BCH0NID)4> chat_client:findUser(birds, 'bob@DESKTOP-BCH0NID').
User named 'bob@DESKTOP-BCH0NID' exists. 
ok

(alice@DESKTOP-BCH0NID)5> chat_client:findUser(birds, 'mary@DESKTOP-BCH0NID').
User named 'mary@DESKTOP-BCH0NID' DOES NOT exist! 
ok

Searching for a group

(alice@DESKTOP-BCH0NID)6> chat_client:findGroup(birds). 
Group named 'birds' exists.
ok

(alice@DESKTOP-BCH0NID)7> chat_client:findGroup(wolves). 
Group named 'wolves' DOES NOT exist!
ok

Listing users in a group

(alice@DESKTOP-BCH0NID)8> chat_client:listUsers(birds). 

Users: ['bob@DESKTOP-BCH0NID','alice@DESKTOP-BCH0NID']
['bob@DESKTOP-BCH0NID','alice@DESKTOP-BCH0NID']

Viewing chat-history for a group

(alice@DESKTOP-BCH0NID)9> chat_client:viewHistory(birds).
---Chat history of group named 'birds'---
---START---
'Alice':
 "Hello from Alice, the parrot :)" -- ['2021-05-22 12:17:02']

'Bob':
 "Hello, Alice. Welcome to the group!" -- ['2021-05-22 12:20:06']

ok