The short answer:
io.sockets.adapter.rooms

I analysed io:

The sockets output part from io as shown in that answer contains the following:

sockets: 
   { manager: [Circular],
     name: '',
     sockets: { '210837319844898486': [Object] },
     auth: false,
     flags: { endpoint: '', exceptions: [] },
     _events: { connection: [Function] } },

Where is the adapter? Where are the rooms?

What is the way to find out adapter and rooms from the output of io?

https://stackoverflow./a/6727354/462608

The short answer:
io.sockets.adapter.rooms

I analysed io:

The sockets output part from io as shown in that answer contains the following:

sockets: 
   { manager: [Circular],
     name: '',
     sockets: { '210837319844898486': [Object] },
     auth: false,
     flags: { endpoint: '', exceptions: [] },
     _events: { connection: [Function] } },

Where is the adapter? Where are the rooms?

What is the way to find out adapter and rooms from the output of io?

• javascript
• node.js
• sockets
• io

3 Answers 3

I think you are trying to get room before joining it. First You have to Join room and than you can get the rooms in io.sockets.adapter.rooms You can checkout this link to know rooms

let room_id = 111

io.sockets.on("connection", function (socket) {
    // Everytime a client logs in, display a connected message
    console.log("Server-Client Connected!");
    socket.join("_room" + room_id);
    socket.on('connected', function (data) {

    });
    console.log(io.sockets.adapter.rooms);
    socket.on('qr_code_scan', function (room_id) {
        io.sockets.in("_room" + room_id).emit("qr_code_scan", true);
    });
});

Log of io.sockets.adapter.rooms

{bjYiUV5YZy54VedKAAAA: Room, _room111: Room}
app.js:55
_room111:Room {sockets: {…}, length: 1}
length:1
sockets:{-isBAZIB-Sm3jArgAAAB: true}
-isBAZIB-Sm3jArgAAAB:true
__proto__:Object
__proto__:Object
-isBAZIB-Sm3jArgAAAB:Room {sockets: {…}, length: 1}
length:1
sockets:{-isBAZIB-Sm3jArgAAAB: true}
-isBAZIB-Sm3jArgAAAB:true
__proto__:Object
__proto__:Object
__proto__:Object

For the current version of "socket.io": "^4.1.2",

io.sockets.adapter.rooms

is a Map like this:

Map(2) { 'hgdAp3ghn1RQZk3iAAAD' => Set(1) { 'hgdAp3ghn1RQZk3iAAAD' }, 'test' => Set(1) { 'hgdAp3ghn1RQZk3iAAAD' } }

when a room already exist, in this case 'test'.

If you invoke it before a room has been created, then it'd be:

Map(1) { 'w2e2Vnav-zmf6pm4AAAD' => Set(1) { 'w2e2Vnav-zmf6pm4AAAD' } }

Thus the long answer is that it depends on the version you are using, and that for version 4.x the room will only be part of the map after an user has joined the room, not before.

I'm not sure what's up with that response. But I can confirm that when I run a basic socket.io example (codesandbox link) using [email protected] and console.log(io) I see the following in my terminal:

Server {
  nsps: {
    '/': Namespace {
      name: '/',
      server: [Circular],
      sockets: [Object],
      connected: [Object],
      fns: [],
      ids: 0,
      rooms: [],
      flags: {},
      adapter: [Adapter],
      _events: [Object: null prototype],
      _eventsCount: 1
    }
  },
  parentNsps: Map {},
  _path: '/socket.io',
  _serveClient: true,
  parser: {
    protocol: 4,
    types: [
      'CONNECT',
      'DISCONNECT',
      'EVENT',
      'ACK',
      'ERROR',
      'BINARY_EVENT',
      'BINARY_ACK'
    ],
    CONNECT: 0,
    DISCONNECT: 1,
    EVENT: 2,
    ACK: 3,
    ERROR: 4,
    BINARY_EVENT: 5,
    BINARY_ACK: 6,
    Encoder: [Function: Encoder],
    Decoder: [Function: Decoder]
  },
  encoder: Encoder {},
  _adapter: [Function: Adapter],
  _origins: '*:*',
  sockets: Namespace {
    name: '/',
    server: [Circular],
    sockets: { WFrro9MpS4d1nSouAAAA: [Socket] },
    connected: { WFrro9MpS4d1nSouAAAA: [Socket] },
    fns: [],
    ids: 0,
    rooms: [],
    flags: {},
    adapter: Adapter {
      nsp: [Circular],
      rooms: [Object],
      sids: [Object],
      encoder: Encoder {}
    },
    _events: [Object: null prototype] { connection: [Array] },
    _eventsCount: 1
  },
  eio: Server {
    clients: { WFrro9MpS4d1nSouAAAA: [Socket] },
    clientsCount: 1,
    wsEngine: 'ws',
    pingTimeout: 5000,
    pingInterval: 25000,
    upgradeTimeout: 10000,
    maxHttpBufferSize: 100000000,
    transports: [ 'polling', 'websocket' ],
    allowUpgrades: true,
    allowRequest: [Function: bound ],
    cookie: 'io',
    cookiePath: '/',
    cookieHttpOnly: true,
    perMessageDeflate: { threshold: 1024 },
    httpCompression: { threshold: 1024 },
    initialPacket: [ '0' ],
    ws: WebSocketServer {
      _events: [Object: null prototype] {},
      _eventsCount: 0,
      _maxListeners: undefined,
      options: [Object],
      [Symbol(kCapture)]: false
    },
    _events: [Object: null prototype] { connection: [Function: bound ] },
    _eventsCount: 1
  },
  httpServer: Server {
    insecureHTTPParser: undefined,
    _events: [Object: null prototype] {
      connection: [Function: connectionListener],
      close: [Function: bound ],
      listening: [Function: bound ],
      upgrade: [Function],
      request: [Function]
    },
    _eventsCount: 5,
    _maxListeners: undefined,
    _connections: 2,
    _handle: TCP {
      reading: false,
      onconnection: [Function: onconnection],
      [Symbol(owner_symbol)]: [Circular]
    },
    _usingWorkers: false,
    _workers: [],
    _unref: false,
    allowHalfOpen: true,
    pauseOnConnect: false,
    httpAllowHalfOpen: false,
    timeout: 120000,
    keepAliveTimeout: 5000,
    maxHeadersCount: null,
    headersTimeout: 60000,
    _connectionKey: '6::::8080',
    [Symbol(IningMessage)]: [Function: IningMessage],
    [Symbol(ServerResponse)]: [Function: ServerResponse],
    [Symbol(kCapture)]: false,
    [Symbol(asyncId)]: 6
  },
  engine: Server {
    clients: { WFrro9MpS4d1nSouAAAA: [Socket] },
    clientsCount: 1,
    wsEngine: 'ws',
    pingTimeout: 5000,
    pingInterval: 25000,
    upgradeTimeout: 10000,
    maxHttpBufferSize: 100000000,
    transports: [ 'polling', 'websocket' ],
    allowUpgrades: true,
    allowRequest: [Function: bound ],
    cookie: 'io',
    cookiePath: '/',
    cookieHttpOnly: true,
    perMessageDeflate: { threshold: 1024 },
    httpCompression: { threshold: 1024 },
    initialPacket: [ '0' ],
    ws: WebSocketServer {
      _events: [Object: null prototype] {},
      _eventsCount: 0,
      _maxListeners: undefined,
      options: [Object],
      [Symbol(kCapture)]: false
    },
    _events: [Object: null prototype] { connection: [Function: bound ] },
    _eventsCount: 1
  }
} 

With the rooms in io.sockets.adapter.rooms.