CN 2025 Project Phase 2

B12901066吳孟峰、B12902106何易儒

Compilation instructions

To compile server.cpp and client.cpp, run

cd code # go to code/
make

This will create a \bin folder containing two binaries.

Then, to run the server program, use

cd .. # go back to main folder
./bin/server [port]

To run the client program, use

./bin/client [server_ip] [server_port]

For example,

./bin/server 8888
./bin/client 127.0.0.1 8888

Finally, to remove all files in \bin, use

make clean

Usage (commands)

register <username> <password>

Register a new account on the server. Use this only when the client is not logged in.

• Format: register alice s3cr3t
• Success: Server confirms "Register successed".
• Failure: Username already exists or user is already logged in.

login <username> <password> <client_listen_port>

Authenticate and mark the user as online. The <client_listen_port> is the local port this client will open to accept direct Peer-to-Peer (P2P) connections.

• Format: login alice s3cr3t 9001
• Success: Server confirms login, starts a listener thread on the specified port, and marks the user as online.
• Failure: Wrong username/password, port conflict (port already used by another user or valid range error), or user already logged in.

logout

Log out the currently logged-in user and mark them as offline on the server.

• Format: logout
• Success: Server confirms "Logout successed".
• Failure: If no user is currently logged in.

list

Request the server to return the list of currently online users.

• Format: list
• Success: Server displays a list of online usernames.
• Failure: If the client is not logged in.

chat <username>

Initiate a private P2P chat session with another online user. The client queries the server for the target's IP/Port, then connects directly.

• Format: chat bob
• Success: Target accepts the request (y), and both users enter Chat Mode.
• Failure: Target rejects the request (n), target is offline, or connection errors.
• Note: Inside Chat Mode, type _exit to quit the chat and return to the main menu.

group

Request the list of all available chat groups currently active on the server.

• Format: group
• Success: Server lists all existing group names.
• Failure: If the client is not logged in.

create <groupname>

Create a new chat group on the server.

• Format: create study_group
• Success: Server confirms "Create successed".
• Failure: Group name already exists or user is not logged in.

join <groupname>

Join an existing group chat. This initiates Group Mode, allowing messages to be broadcast to all group members.

• Format: join study_group
• Success: Client enters the group room and loads chat history.
• Failure: Group does not exist or connection errors.
• Note: Inside Group Mode, type _exit to leave the room and return to the main menu.

send <username> <filename>

Send a file to another online user via a direct P2P connection.

• Format: send bob homework.txt
• Success: Target accepts the transfer (y,save_path) and the file is transmitted successfully.
• Failure: Target rejects (n), file does not exist locally, or connection errors.

quit

Terminate the client process. If a user is logged in, the client sends a quit signal to the server before exiting.

• Format: quit
• Behavior: Cleanly disconnects from the server and closes the application.