IRsea

About

A chatting application, designed along the lines of IRC. Made as a course assignment for Network Security (CSE550). The following commands are supported :

• /register <USERNAME> <PASSWORD> : register yourself with the server
• /login <USERNAME> <PASSWORD> : login to access the commands below
• /exit : log out and exit from the service
• /who : see all the users who're logged in right now
• /msg <USERNAME> <MESSAGE> : send a message to a specific user
• /create_grp <GROUP_NAME> : create a group
• /join_grp <GROUP_NAME> : join an existing group
• /msg_group <MESSAGE> : broadcast a message to an entire group which you've currently joined
• /send <USERNAME> <FILENAME> : send a file to another user
• /recv : receive file being sent by someone

Working

Server

• Four threads work in parallel.
• One thread listens on the port assigned for registration of users.
• One thread clears the outgoing message queue by sending data to respective group users.
• One thread clears the outgoing message queue by sending data to respective users.
• One thread creates a new thread (for communication) for every incoming request by the client. This thread is deleted once the client is done with their interaction with the server.

Client

• Two threads work in parallel.
• One thread listens to the server for incoming data (which may be sent by the server itself, or data redirected by the server).
• One thread is for HCI; sending data to the server as the user requests.

Running it

• To run the server, run: make. Then, run it as ./server (from server folder).
• To run a client, run: make. Then, run it as ./client <SERVER ADDRESS> (from client folder)
• If you don't mind concurrency bugs, run: make. Then, run it as ./server (from server(no_locks) folder).
• Run make clean to remove compiled programs.

Specifics

• Default user (hello,world) for testing.
• Mutex locks are inserted around every shared variable to ensure concurrency.
• Maximum length per message: 512 characters.
• Creating group (on the client's end) is not enough to send messages to that group; joining is required as well.
• /recv will create a file by the name of 'file_from_server'. To receive more files (and avoid them overwriting this file), move the file to some other location after receiving it.
• Files pushed to ther server are stored in the folder 'temp_data'.
• strtok() is not thread safe (as standard implementation doesn't use TLS). Thus, strtok_r() has been used.
• 'User is offline/doesn't exist' is flashed to the client if they try messaging a user who is offline or doesn't exist (further specification isn't provided to avoid any secutiry attacks).

Cases tested (& handled)

• Register via client.
• Register and then logs in.
• Already registered user logs in.
• Unregistered user tries to log in.
• Logged in user tries to log in again.
• Joining a non-existent group.
• Messaging a group they haven't joined/not part of.
• Sending a message to group after joining it.
• Sending message to user who doesn't exist/isn't online.
• Sending file to user who's online, sending file to yourself.
• Sending file to user who doesn't exist/isn't online.
• Sending file, going offline, and then the reciepent downloads it.
• Server shuts down in between.
• Client shuts down their service unexpectedly.
• Checking who's online.
• Messages sent to a group do not come back to the sender (as it doesn't make sense).
• Any message received includes, in brackets, name of the user/group from which it is.
• User tries sending a file that doesn'r exist on their system.
• Messages from people have username in brackets, messages from groups have group's name in square brackets.
• Multiple files waiting for a person to receive (multiset is used in backend, so a person can have multiple pending files).
• A message is sent to the reciepent whenever a file is sent for them by anyone.

Example (for client)

>> Welcome to IRsea!
/register test user
>> Registered!
/login hello world
>> Signed in!
/who
>> hello
random_user
/msg random_user what's up?
>> (random_user)  nothing much
/create_grp random
>> Group created!
/join_grp random
>> Joined group!
>> [random_user] hi, random user :)
/send random_user Makefile                    
>> File sent to server!
/recv
>> File received!
random_command
>> Invalid command! Please read the README for the list of supported commands
/exit
>> Exiting!
Thanks for using IRsea!