# Djumbai

A UNIX local messaging service

## Components

1. **Initiation of Message Sending:**
   - A Unix user initiates a message sending process using a Command Line Interface (CLI) tool.

2. **Creation of Processes:**
   - The CLI tool spawns a process called `djumbai-client-send`. This process runs under the context of the initiating Unix user.
   - `djumbai-client-send` spawns another process called `djumbai-enqueue`, which operates under the `djumbaiq` user context.

3. **Message Queuing:**
   - `djumbai-enqueue` process writes the message to a message queue, which functions as a named pipe. This queue acts as an intermediary storage for the message.

4. **Message Retrieval:**
   - The `djumbai-dequeue` process, functioning as a daemon, runs under the `djumbaid` user context. Its purpose is to retrieve messages from the message queue.

5. **Message Transmission:**
   - Once messages are retrieved, `djumbai-dequeue` sends them to the `djumbai-send` process. This process operates with root privileges.

6. **Receiving and Delivery:**
   - `djumbai-send` spawns a process named `djumbai-client-receive`, which operates under the context of the user/group intended to receive the message.
   - `djumbai-client-receive` writes the received message to the recipient's message-box.

7. **Message Retrieval by User:**
   - The recipient Unix user can utilize the CLI tool at any time to read messages stored in their inbox.

This structured breakdown elucidates the sequential steps involved in the Unix message sending process, including process spawning, message queuing, retrieval, transmission, and eventual delivery to the intended recipient.


## Cenas concretas

Mail queue - FIFO em /opt/djumbai/fifos/message_queue e so pode ser acedida por users do grupo djumbai_queue, que contem djumbai_enqueue e djumbai_dequeue

Send FIFO - FIFO em /opt/djumbai/fifos/send_fifo e so pode ser acedida por users do grupo djumbai_send, que contem djumbai_dequeue e djumbai_send

Mailbox pessoal _ Diretoria em /opt/djumbai/user/$uid/mailbox, que so pode ser acedida pelo user com UID $uid

SentBox pessoal - Diretoria em /opt/djumbai/user/$uid/sentbox, que so pode ser acedida pelo user com UID $uid

Mailbox grupo - Diretoria em /opt/djumbai/group/$gid/mailbox, que so pode ser acedida pelo grupo com GID $gid