News Dissemination System

Objectives

This code implements a news dissemination system using various communication techniques and the TCP/IP protocol stack, particularly UDP, TCP, and IP multicast.

Application Features

Architecture

The news application consists of several components:

• Server:

  • Authenticates and accepts client connections.
  • Manages topics and client subscriptions.
  • Sends multicast addresses to clients for news topics.
  • Communicates with clients over TCP and the administration console over UDP.

• Administration Console:

  • Communicates with the server via UDP.
  • Manages users and configures the application.

• Client:

  • Communicates with the server via TCP.
  • Subscribes to news topics and receives news via multicast.
  • May send news if permitted.

Clients must authenticate with the server using a username and password registered by the administrator. Clients are either subscribers or publishers, based on their permissions.

Server Functionality

• Manage News Topics:

  • Inform clients of available topics and manage client subscriptions.
  • Authenticate clients and manage permissions (subscribers or publishers).
  • Provide multicast addresses for subscribed topics.

• User Management:

  • Manage users with login, password, and permissions, stored in a file.
  • Admin can use a command-line interface (CLI) over UDP to:
    • Add or delete users.
    • List users.
    • Exit the console.
    • Shut down the server.
  • Admin authentication is required to access the CLI.

• Client Access:

  • Validate client access with username and password.
  • Provide information about topics the client is associated with.
  • Handle topic subscription requests and provide multicast addresses.

• Concurrency:

  • Support simultaneous connections from multiple clients.

Server Command Syntax:

news_server {NEWS_PORT} {CONFIG_PORT} {config_file}

Client Functionality

Subscriber Client:

• Authenticate with username and password.
• List topics and subscribe to them.
• Receive news via multicast.
• Remove client from all groups upon exit.

Publisher Client:

• In addition to subscriber functions, can create topics and send news to the multicast group.

Client Command Syntax

news_client {server_address} {NEWS_PORT}

Communication Protocols

• TCP: Used for communications between clients and the server.
• UDP: Used for communications between the server and the administration console.
• Multicast: Used for distributing news to subscribed clients.

Administration Console Commands

• Add user: ADD_USER {username} {password} {admin/client/journalist}
• Delete user: DEL {username}
• List users: LIST
• Exit console: QUIT
• Shut down server: QUIT_SERVER