IO

Exposed as the io namespace in the standalone build, or the result of calling require("socket.io-client").

<script src="/socket.io/socket.io.js"></script>
<script>
  const socket = io("http://localhost");
</script>

const io = require("socket.io-client");
// or with import syntax
import { io } from "socket.io-client";

io.protocol

• (Number)

The protocol revision number (currently: 5).

The protocol defines the format of the packets exchanged between the client and the server. Both the client and the server must use the same revision in order to understand each other.

You can find more information here.

io([url][, options])

• url (String) (defaults to window.location)
• options (Object)
  • forceNew (Boolean) whether to reuse an existing connection
• Returns Socket

Creates a new Manager for the given URL, and attempts to reuse an existing Manager for subsequent calls, unless the multiplex option is passed with false. Passing this option is the equivalent of passing "force new connection": true or forceNew: true.

A new Socket instance is returned for the namespace specified by the pathname in the URL, defaulting to /. For example, if the url is http://localhost/users, a transport connection will be established to http://localhost and a Socket.IO connection will be established to /users.

Query parameters can also be provided, either with the query option or directly in the url (example: http://localhost/users?token=abc).

const io = require("socket.io-client");

const socket = io("ws://example.com/my-namespace", {
  reconnectionDelayMax: 10000,
  auth: {
    token: "123"
  },
  query: {
    "my-key": "my-value"
  }
});

is the short version of:

const { Manager } = require("socket.io-client");

const manager = new Manager("ws://example.com", {
  reconnectionDelayMax: 10000,
  query: {
    "my-key": "my-value"
  }
});

const socket = manager.socket("/my-namespace", {
  auth: {
    token: "123"
  }
});

See new Manager(url[, options]) for the list of available options.

Please note: manager.socket("/my-namespace", options ) will only read the auth key in the options object.
query: {…} and other optional values are only used when passed via a new Manager(uri, options) instance.

See Migrating from 2.x to 3.0 for more on the difference between the auth and query options.