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This functionality was removed in [1] (included in 3.0.0), but
catch-all listeners and socket middleware features are complementary
rather than mutually exclusive.
The only difference with the previous implementation is that passing an
error to the `next` handler will create an error on the server-side,
and not on the client-side anymore.
```js
io.on("connection", (socket) => {
socket.use(([ event, ...args ], next) => {
next(new Error("stop"));
});
socket.on("error", (err) => {
// to restore the previous behavior
socket.emit("error", err);
// or close the connection, depending on your use case
socket.disconnect(true);
});
});
```
This creates additional possibilities about custom error handlers, which
may be implemented in the future.
```js
// user-defined error handler
socket.use((err, [ event ], next) => {
// either handle it
socket.disconnect();
// or forward the error to the default error handler
next(err);
});
// default error handler
socket.use((err, _, next) => {
socket.emit("error", err);
});
```
Related: https://github.com/socketio/socket.io/issues/3678
[1]: 5c73733985