The meaning is not modified: this packet type is still used by the
server when the connection to a namespace is refused.
Breaking change: the Socket instance will now emit a "connect_error"
event instead of "error" (which is not a reserved event anymore)
```js
// before
socket.on("error", () => {});
// after
socket.on("connect_error", () => {});
```
Inspired from EventEmitter2 [1]
The API is similar to the one on the server-side:
```js
socket.onAny((event, ...args) => {});
socket.prependAny((event, ...args) => {});
socket.offAny(); // remove all listeners
socket.offAny(listener);
const listeners = socket.listenersAny();
```
[1]: https://github.com/EventEmitter2/EventEmitter2
Inspired from EventEmitter2 [1]
```js
io.on("connect", socket => {
socket.onAny((event, ...args) => {});
socket.prependAny((event, ...args) => {});
socket.offAny(); // remove all listeners
socket.offAny(listener);
const listeners = socket.listenersAny();
});
```
Breaking change: the socket.use() method is removed
This method was introduced in [2] for the same feature (having a
catch-all listener), but there were two issues:
- the API is not very user-friendly, since the user has to know the structure of the packet argument
- it uses an ERROR packet, which is reserved for Namespace authentication issues (see [3])
[1]: https://github.com/EventEmitter2/EventEmitter2
[2]: https://github.com/socketio/socket.io/issues/434
[3]: https://github.com/socketio/socket.io-protocol
The meaning is not modified: this packet type is still used by the
server when the connection to a namespace is refused. But I feel the
name makes more sense:
```js
socket.on("connect", () => {});
socket.on("connect_error", () => {});
// instead of
socket.on("error", () => {});
```
Depending on the adapter, Socket#join() may return:
- nothing (in-memory and Redis adapters)
- a promise (custom adapters)
Breaking change: Socket#join() and Socket#leave() do not accept a
callback argument anymore.
Before:
```js
socket.join("room1", () => {
io.to("room1").emit("hello");
});
```
After:
```
socket.join("room1");
io.to("room1").emit("hello");
// or await socket.join("room1"); for custom adapters
```
Note: the need for an asynchronous method came from the Redis adapter,
which did override the Adapter#add() method in earlier versions, but
this is not the case anymore.
Reference:
- https://github.com/socketio/socket.io/blob/2.3.0/lib/socket.js#L236-L258
- https://github.com/socketio/socket.io-adapter/blob/1.1.2/index.js#L56-L65
- 05f926e13e
Related: https://github.com/socketio/socket.io/issues/3662
The Access-Control-Allow-xxx headers added by the cors middleware were
overwritten when sending an error response.
Those lines should have been removed in [1].
[1]: 61b949259e
Related: https://github.com/socketio/engine.io/issues/605
These extension points may be used by another adapter, in order to open
or close a connection to a database for example.
In Socket.IO v2, the join() method did accept a callback:
```js
socket.join("room1", () => {
io.to("room1").emit("hello");
});
```
Depending on the adapter, it may now return a promise:
```js
await socket.join("room1");
io.to("room1").emit("hello");
```
Related: https://github.com/socketio/socket.io/issues/3662
A volatile packet will be dropped if:
- the socket is not connected
- the low-level transport is not ready (for example, a HTTP POST request is already pending)
Syntax:
```js
socket.volatile.emit("volatile event", "might or might not be sent");
```
In order to be able to cast it on the argument of the "connect" event:
```js
import { Socket } from "socket.io";
io.on("connect", (socket: Socket) => {
// ...
});
```
The client bundles are included in the repository in order to remove
socket.io-client from the list of production dependencies and thus to
reduce the total number of dependencies when installing the server.
This means the release of the client and the server must now be in sync
(which is almost always the case actually).
The minified build is now served:
- /<path>/socket.io.js
- /<path>/socket.io.js.map
- /<path>/socket.io.min.js
- /<path>/socket.io.min.js.map
The content will now be compressed as well.
There are two issues with the typings:
- on the client-side, the Emitter class is not properly imported (hence the @ts-ignore)
- on the server-side, the Socket class is not exported (in order to cast it in the "connect" event)
Both the "connected" and the "_sockets" maps were used to track the
Socket instances in the namespace.
Let's merge them into "sockets". It's a breaking change, but:
- the "sockets" object did already exist in Socket.IO v2 (and appears in some examples/tutorials)
- "sockets" makes more sense than "connected" in my opinion
- there was already a breaking change regarding the "connected" property (from object to Map)
Breaking change: the "connected" map is renamed to "sockets"
After a given timeout, a client that did not join any namespace will be
closed in order to prevent malicious clients from using the server
resources.
The timeout defaults to 45 seconds, in order not to interfere with the
Engine.IO heartbeat mechanism (30 seconds).
The binary detection was moved from the parser to the client/server in
[1], in order to allow the user to skip the binary detection for huge
JSON payloads.
```js
socket.binary(false).emit(...);
```
The binary detection is needed in the default parser, because the
payload is encoded with JSON.stringify(), which does not support binary
content (ArrayBuffer, Blob, ...).
But other parsers (like [2] or [3]) do not need this check, so we'll
move the binary detection back here and remove the socket.binary()
method, as this use case is now covered by the ability to provide your
own parser.
Note: the hasBinary method was copied from [4].
[1]: f44256c523
[2]: https://github.com/darrachequesne/socket.io-msgpack-parser
[3]: https://github.com/darrachequesne/socket.io-json-parser
[4]: https://github.com/darrachequesne/has-binary
