This project is a hybrid instant messaging application that combines Client-Server and Peer-to-Peer (P2P) communication models. The application enables users to engage in one-to-one chats or group conversations, offering flexibility and efficient resource utilization.

• One-to-One Chat:
  Users can start private chats. Device information (ID and port) is fetched from the server, and a direct P2P connection is established, offloading communication from the server.

• Group Chat:
  Users in a one-to-one chat can seamlessly add others to form a group. Each participant creates direct P2P sockets with every other participant, ensuring decentralized communication.

• Offline Messaging:
  Messages sent to offline or busy users are stored on the server in a dedicated "pending messages" directory. These are delivered when the recipient becomes available.

• Crash Handling:
  Devices detect crashes based on communication errors and update their connections accordingly to maintain an uninterrupted experience for active users.

• Chat History:
  Maintains message history for one-to-one chats for reference and continuity.

• File Sharing:
  Files can be shared using the /s command. Received files are saved locally for easy access.

• User Directory and Contact List:
  A built-in directory system stores usernames and contact details, while a dynamic chatDevices variable tracks active chats.

• Server Recovery:
  Server states are saved upon disconnection in a server_info.txt file for smooth recovery during restarts.

• Timestamps:
  User activity is tracked with timestamps formatted as HH:MM:SS, dynamically updated with a tempo_attuale() function.

• Socket Programming: Ensures real-time communication.
• Hybrid Architecture: Combines the benefits of Client-Server and Peer-to-Peer models.
• File Management: For offline message storage, contact directory, and server persistence.

1. Clone this repository.
2. Start the server to manage user data and offline messages.
3. Launch the client application to initiate one-to-one or group chats, or share files using the /s command.

To test file sharing:

• Share a file named fileprova.txt.
• Check the received file in recv.txt.

Developer: Francesco Moretti
University: University of Pisa, Computer Networks (2022/2023)