Socket.io Client: respond to all events with one handler?

Question

Is it possible to have a socket.io client respond to all events without to have specify each event individually?

For example, something like this (which obviously doesn't work right now):

var socket = io.connect("http://myserver");

socket.on("*", function(){
  // listen to any and all events that are emitted from the
  // socket.io back-end server, and handle them here.

  // is this possible? how can i do this?
});

I want this callback function to be called when any / all events are received by the client-side socket.io code.

Is this possible? How?

I opened the following issue on forwarding all event types, I've also been adding the solutions I found: https://github.com/Automattic/socket.io/issues/1715 — Peter Uithoven, Aug 27 '14 at 19:41

Flion · Answer 1 · 2016-07-04T14:32:05.863

89

Updated solution for socket.io-client 1.3.7

var onevent = socket.onevent;
socket.onevent = function (packet) {
    var args = packet.data || [];
    onevent.call (this, packet);    // original call
    packet.data = ["*"].concat(args);
    onevent.call(this, packet);      // additional call to catch-all
};

Use like this:

socket.on("*",function(event,data) {
    console.log(event);
    console.log(data);
});

None of the answers worked for me, though the one of Mathias Hopf and Maros Pixel came close, this is my adjusted version.

NOTE: this only catches custom events, not connect/disconnect etc

edited Jul 04 '16 at 14:32

answered Nov 27 '15 at 14:58

Flion

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2

Thank you, this helped me debug missing events! – Maitreya May 19 '16 at 08:02
1

Unfortunately not working with things like 'user.*';. Maybe I can manage to implement it. – C4d Mar 16 '17 at 16:54
Hi, very good, but it could be helpful if you could have some output examples ^^ I feel like I need to run the code to understand your answer :) – TOPKAT Oct 03 '19 at 16:47

score 26 · Accepted Answer · answered May 01 '12 at 22:18

26

It looks like the socket.io library stores these in a dictionary. As such, don't think this would be possible without modifying the source.

From source:

EventEmitter.prototype.on = function (name, fn) {
    if (!this.$events) {
      this.$events = {};
    }

    if (!this.$events[name]) {
      this.$events[name] = fn;
    } else if (io.util.isArray(this.$events[name])) {
      this.$events[name].push(fn);
    } else {
      this.$events[name] = [this.$events[name], fn];
    }

    return this;
  };

answered May 01 '12 at 22:18

lukiffer

11,025
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3

also found this: http://stackoverflow.com/questions/8832414/overriding-socket-ios-emit-and-on/8838225 – Derick Bailey May 02 '12 at 00:59
In 2019 I don't think this is the case anymore. – Urasquirrel Jun 09 '19 at 00:17

score 25 · Answer 3 · answered May 11 '16 at 10:07

25

Finally, there is a module called socket.io-wildcard which allows using wildcards on client and server side

var io         = require('socket.io')();
var middleware = require('socketio-wildcard')();

io.use(middleware);

io.on('connection', function(socket) {
  socket.on('*', function(){ /* … */ });
});

io.listen(8000);

answered May 11 '16 at 10:07

Marian Klühspies

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Is it possible that the callback does not fired on `disconnect` only? – gazdagergo Aug 20 '21 at 11:15

score 11 · Answer 4 · answered Oct 14 '12 at 17:41

Here you go ...

var socket = io.connect();
var globalEvent = "*";
socket.$emit = function (name) {
    if(!this.$events) return false;
    for(var i=0;i<2;++i){
        if(i==0 && name==globalEvent) continue;
        var args = Array.prototype.slice.call(arguments, 1-i);
        var handler = this.$events[i==0?name:globalEvent];
        if(!handler) handler = [];
        if ('function' == typeof handler) handler.apply(this, args);
        else if (io.util.isArray(handler)) {
            var listeners = handler.slice();
            for (var i=0, l=listeners.length; i<l; i++)
                listeners[i].apply(this, args);
        } else return false;
    }
    return true;
};
socket.on(globalEvent,function(event){
    var args = Array.prototype.slice.call(arguments, 1);
    console.log("Global Event = "+event+"; Arguments = "+JSON.stringify(args));
});

This will catch events like connecting, connect, disconnect, reconnecting too, so do take care.

Socket.IO.js build:0.9.10, development. – Kaustubh Karkare Oct 14 '12 at 17:56 — Kaustubh Karkare, Oct 14 '12 at 17:56
Did this end up in a release? – hacklikecrack Nov 23 '13 at 11:16 — hacklikecrack, Nov 23 '13 at 11:16

leszek.hanusz · Answer 5 · 2016-08-18T10:44:00.777

9

Note: this answer is only valid for socket.io 0.x

You can override socket.$emit

With the following code you have two new functions to:

Trap all events
Trap only events which are not trapped by the old method (it is a default listener)

var original_$emit = socket.$emit;
socket.$emit = function() {
    var args = Array.prototype.slice.call(arguments);
    original_$emit.apply(socket, ['*'].concat(args));
    if(!original_$emit.apply(socket, arguments)) {
        original_$emit.apply(socket, ['default'].concat(args));
    }
}

socket.on('default',function(event, data) {
    console.log('Event not trapped: ' + event + ' - data:' + JSON.stringify(data));
});

socket.on('*',function(event, data) {
    console.log('Event received: ' + event + ' - data:' + JSON.stringify(data));
});

edited Aug 18 '16 at 10:44

answered Oct 01 '13 at 16:10

leszek.hanusz

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Any advice on an aync operation before calling apply. setTimeout(function() { original_$emit.apply(socket, ['*'].concat(args)); if(!original_$emit.apply(socket, arguments)) { original_$emit.apply(socket, ['default'].concat(args)); } }, 2000); – Enki Mar 15 '14 at 19:58
I'm using Socket.IO 1.3.6 and there doesn't seem to be a $emit method in `socket` anymore – raimohanska Sep 28 '15 at 13:47
Indeed. Check @Flion answer for 1.x versions – leszek.hanusz Aug 18 '16 at 10:47

score 9 · Answer 6 · answered Nov 27 '20 at 11:42

9

As it is in v3.0 documentation:

socket.onAny((event, ...args) => {
  console.log(`got ${event}`);
});

answered Nov 27 '20 at 11:42

Carlos Oliveira

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23

Dan Dascalescu · Answer 7 · 2013-04-20T11:58:17.810

The current (Apr 2013) GitHub doc on exposed events mentions a socket.on('anything'). It appears that 'anything' is a placeholder for a custom event name, not an actual keyword that would catch any event.

I've just started working with web sockets and Node.JS, and immediately had a need to handle any event, as well as to discover what events were sent. Can't quite believe this functionality is missing from socket.io.

score 6 · Answer 8 · answered May 16 '17 at 22:38

socket.io-client 1.7.3

As of May 2017 couldn't make any of the other solutions work quite how i wanted - made an interceptor, using at Node.js for testing purposes only:

var socket1 = require('socket.io-client')(socketUrl)
socket1.on('connect', function () {
  console.log('socket1 did connect!')
  var oldOnevent = socket1.onevent
  socket1.onevent = function (packet) {
    if (packet.data) {
      console.log('>>>', {name: packet.data[0], payload: packet.data[1]})
    }
    oldOnevent.apply(socket1, arguments)
  }
})

References:

score 4 · Answer 9 · answered May 27 '15 at 22:04

Because your question was pretty general in asking for a solution, I'll pitch this one that requires no hacking the code, just a change in how you use the socket.

I just decided to have my client app send the exact same event, but with a different payload.

socket.emit("ev", { "name" : "miscEvent1"} );
socket.emit("ev", { "name" : "miscEvent2"} );

And on the server, something like...

socket.on("ev", function(eventPayload) {
   myGenericHandler(eventPayload.name);
});

I don't know if always using the same event could cause any issues, maybe collisions of some kind at scale, but this served my purposes just fine.

score 3 · Answer 10 · answered Jun 23 '13 at 08:30

3

There is a long discussion about this topic going on at the Socket.IO repository issue page. There are a variety of solutions posted there (e.g., overriding EventEmitter with EventEmitter2). lmjabreu released another solution a couple weeks ago: a npm module called socket.io-wildcard that patches in a wildcard event onto Socket.IO (works with the current Socket.IO, ~0.9.14).

answered Jun 23 '13 at 08:30

sffc

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4

But that is only serverside... his module is not usable on the clientside (browser) – Sander Jan 06 '14 at 08:57

score 2 · Answer 11 · answered Jan 24 '20 at 13:48

Even though this is a old question, I have the same problem and solved using the native socket in Node.js, which has a event of .on('data'), fired everytime some data comes. So this is what I've done so far:

const net = require('net')

const server = net.createServer((socket) => {
    // 'connection' listener.
    console.log('client connected')

    // The stuff I was looking for
    socket.on('data', (data) => {
        console.log(data.toString())
    })

    socket.on('end', () => {
        console.log('client disconnected')
    })
})

server.on('error', (err) => {
    throw err;
})

server.listen(8124, () => {
    console.log('server bound');
})

score 1 · Answer 12 · answered Apr 30 '15 at 01:04

All methods I found (including socket.io-wildcard and socketio-wildcard) didn't work for me. Apparently there is no $emit in socket.io 1.3.5...

After reading socket.io code, I patched up the following which DID work:

var Emitter = require('events').EventEmitter;
var emit = Emitter.prototype.emit;
[...]
var onevent = socket.onevent;
socket.onevent = function (packet) {
    var args = ["*"].concat (packet.data || []);
    onevent.call (this, packet);    // original call
    emit.apply   (this, args);      // additional call to catch-all
};

This might be a solution for others as well. However, ATM I don't exactly understand why nobody else seems to have issues with the existing "solutions"?!? Any ideas? Maybe it's my old node version (0.10.31)...

I can confirm it works and, as you observed, is the only one which works (in the sense: for me too). Thank you very much! — mark, May 21 '15 at 20:20

score 1 · Answer 13 · answered Jun 24 '15 at 15:15

@Matthias Hopf answer

Updated answer for v1.3.5. There was a bug with args, if you wanna listen on old event and * event together.

var Emitter = require('events').EventEmitter;
var emit = Emitter.prototype.emit;
// [...]
var onevent = socket.onevent;
socket.onevent = function (packet) {
    var args = packet.data || [];
    onevent.call (this, packet);    // original call
    emit.apply   (this, ["*"].concat(args));      // additional call to catch-all
};

score 1 · Answer 14 · answered Jun 06 '22 at 12:39

1

In v4, Socket.IO has Catch-all listeners. For example:

socket.prependAny(() => {
   console.log("This will be fired first");
});

answered Jun 06 '22 at 12:39

Cees Jol

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Your answer could be improved with additional supporting information. Please [edit](https://stackoverflow.com/posts/72517845/edit) to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers in the [help center](https://stackoverflow.com/help/how-to-answer). – Ethan Jun 07 '22 at 20:30

score 0 · Answer 15 · edited Sep 21 '18 at 01:51

I'm using Angular 6 and the npm package: ngx-socket-io

import { Socket } from "ngx-socket-io";

...

constructor(private socket: Socket) { }

...

After connect the socket, I use this code, this is handling all custom events...

const onevent = this.socket.ioSocket.onevent;
this.socket.ioSocket.onevent = function (packet: any) {
  const args = packet.data || [];
  onevent.call(this, packet);    // original call
  packet.data = ["*"].concat(args);
  onevent.call(this, packet);      // additional call to catch-all
};
this.socket.on("*", (eventName: string, data: any) => {
  if (typeof data === 'object') {
    console.log(`socket.io event: [${eventName}] -> data: [${JSON.stringify(data)}]`);
  } else {
    console.log(`socket.io event: [${eventName}] -> data: [${data}]`);
  }
});

Socket.io Client: respond to all events with one handler?

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