sequenceDiagram

```mermaid
sequenceDiagram
  participant U as User (view in browser)
  participant C as Client (1st person, bundle from :3001)
  participant S as Server (express @ :3000)
  participant R as Room (clients sub'd to room)
  participant O as Other Users (view in browser)

  U->>C: click LOGIN
  C->>S: POST http://hostname:3000/login
  Note right of C: Origin: http://hostname:3001<br>Sec-Fetch-Site: cross-site<br>Referrer: http://host:3001/
  S->>C: 200 OK
  Note left of S: Access-Control-Allow-Origin: *<br>Connection: keep-alive<br>Keep-Alive: timeout=5<br>X-Powered-By: Express<br>Date: Fri, 02 Dec 2022...
  note left of S: JSON: LOGGEDIN object

  U->>C: click CONNECT
  C->>S: GET wss://hostname:3000/
  note right of C: Upgrade: websocket<br>Connection: keep-alive, Upgrade<br>Sec-Fetch-Dest/Mode: websocket<br>Sec-WebSocket-Key: A3be...SQ==
  S->>C: 101 Switching Protocols
  note left of S: Connection: Upgrade<br>Sec-Websocket-Accept: AAswx...KQ=<br>Upgrade: websocket
  note left of S: WS msg: UNICAST_WELCOME
  S->>R: WS BCAST_ENTRY
  R->>O: "system chat line user entry"
  R->>O: [add user to participants list]

  U->>C: enter text, click SEND
  C->>U: "user's own chat line"
  C->>S: SEND_CHAT
  S->>R: BCAST_CHAT
  R->>O: "sending user's chat line"
```