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Channels & Messaging

Campus Connect enables real-time direct messaging between users, organized into channels. This system supports:

  • Direct Messaging (DMs) with unique channel instances
  • Message creation, retrieval, editing, and deletion
  • Channel-based access control via guards
  • Real-time WebSocket updates per channel
ER Diagram 
erDiagram
    USER ||--o{ CHANNEL : participates_in
    USER ||--o{ MESSAGE : sends
    CHANNEL ||--o{ MESSAGE : contains

    USER {
        string _id
        string username
    }

    CHANNEL {
        string _id
        string type
        string name
        string[] participants
    }

    MESSAGE {
        string _id
        string channelId
        string senderId
        string content
        boolean edited
        date createdAt
    }

Channel Types

  • DM: Private channel between two users
  • GROUP: Multi-user channels (not yet implemented)

Endpoints

GET /channels

Returns all channels the current user is a participant in.

POST /channels/channel/getDMChannel

Creates or retrieves a DM channel between the current user and another user.

{ "userId": "targetUserId" }

Messaging

POST /channels/message

Sends a message to a channel.

{
  "channelId": "abc123",
  "content": "Hello world"
}

GET /channels/:channelId/messages

Returns all messages in the specified channel, sorted by creation time.

POST /channels/message/:messageId/edit

Edits a message if the sender matches the current user.

{
  "content": "Edited message content"
}

POST /channels/message/:messageId/delete

Deletes a message if the sender is the current user.

Channel Access Control

All routes are protected by the ChannelsGuard.

  • Verifies the user is a participant in the given channel
  • Allows bypass for DM creation (/channel/getDMChannel)
  • Returns 403 Forbidden if unauthorized

Real-Time Messaging

Messages are emitted to clients using Socket.IO under the /channels namespace.

WebSocket Events

joinChannel

Client joins a Socket.IO room by channel ID.

leaveChannel

Client leaves the specified room.

message.sent (Server Internal)

When a message is sent, the ChannelsGateway listens to this event and broadcasts it via messageReceived.

messageReceived

Clients listening on a channel receive new messages in real-time.

Message Lifecycle

  1. Client sends message via HTTP → POST /channels/message
  2. Backend saves message and emits → message.sent
  3. Gateway receives event and emits to clients in room → messageReceived

WebSocket Authentication

On socket connection, the server:

  • Parses the connect.sid cookie
  • Verifies session with Redis
  • Disconnects unauthenticated clients