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socket.io-monitor

socket.io-monitor

Monitor sockets, rooms, events in your socket.io server. This module includes the server and client libraries.

See socket.io-monitor-cli for a realtime dashboard in your console.

Installation

npm install --save socket.io-monitor

Usage (local)

  1. Bind your socket.io server:
const monitor = require('socket.io-monitor')
const { emitter } = monitor.bind(io, { server: false })
  1. In same process, use emitter to grab info:
emitter.getState()
/* {
  rooms: [ { name: 'room1', sockets: [ 'id1', 'id2' ] }, … ],
  sockets: [ { id: 'id1', connectedAt: 12345 }, { id: 'id2', connectedAt: 56789 }, … ]
*/
 
emitter.on('join', ({ id, rooms }) => console.log('socket %s joins rooms %s', id, rooms))

Usage (remote)

  1. Bind your socket.io server:
const monitor = require('socket.io-monitor')
const { server } = monitor.bind(io, { port: 9042, host: 'localhost' })
 
server.then(srv => {
  console.log('connection OK')
})
  1. In another process, connect to your monitor server:
const monitor = require('socket.io-monitor')
const client = monitor.connect({ port: 9042, host: 'localhost' })
 
client.then(emitter => {
  console.log('connection OK')
  emitter.on('join', ({ id, rooms }) => console.log('socket %s joins rooms %s', id, rooms))
})

Events

  • (remote only) init state
    • (local only) method getState() returns state
  • (local only) client { client, state }
    • client is the remote monitor client (you can listen/emit to all remote events)
    • state is the initial state data, sent along init event
  • broadcast { name, args, rooms, flags }
  • join { id, rooms }
  • leave { id, room }
  • leaveAll { id }
  • connect { id }
  • disconnect { id }
  • emit { id, name, args }
  • recv { id, name, args }
  • string { id, string }
    • this event should be used by monitor client implementation to display alternative string representation of a socket. This event is never emitted for you, see example below.

State

  • rooms: [ { name: string, sockets: [ string ] } ]
  • sockets: [ { id: string, connectedAt: timestamp-ms } ]

Socket string representation

You can emit string event to provide alternative string representation for a socket, that can be used by monitor client.

// Example 1: when user emits a "login" event, we use it as string representation 
const { emitter } = monitor.bind(io, options)
 
io.on('connection', socket => {
  socket.on('login', username => {
    // store somewhere that socket is bound to this username 
    emitter.emit('string', { id: socket.id, string: username })
  })
})

Real-life use case: once a socket is authenticated and bound to a user we put it in a dedicated room user:$username. This is frequently done to be able to target a socket knowing only the username. We take advantage of this situation to only rely on emitter instead of modifying existing code:

const { emitter } = monitor.bind(io, options)
// 'join' event is emitted each time a socket joins a room 
emitter.on('join', ({ id, room }) => {
  // we only have to check if room has the known prefix, and voilà! 
  if (room.match(/^user:/)) {
    emitter.emit('string', { id, string: room.substring(5) })
  }
})

In both cases however, emitting string representation just when a socket connects is not enough: when you connect a monitor client, it will fetch existing sockets and will not receive string events for them. In current version it's up to you to handle this case too. This part may change in the future to make it easier. The current best way is to listen for client event which is called when a monitor client receives state data:

emitter.on('client', (client, state) => {
  // state.rooms = list of rooms with socket ids in them 
  // state.sockets = list of sockets 
  // in our sample, an identified socket is in a room named "user:$username" 
  state.rooms.forEach(({ name, sockets }) => {
    if (name.match(/^user:/)) {
      const id = sockets[0]
      const string = name.substring(5)
      client.emit('string', { id, string })
    }
  })
})