I am running into a problem while using socket.io to do some event handling. For some reason, the following code snippet does not handle the event 'update', or any event for that matter. Let me explain the situation.
I have created a file named updates.js to create a socket.io socket variable named socket_8888 that is bound to port 8888. I then use module.exports to make that socket variable available to any other file that imports updates.js using require('updates.js'). I structured my application this way because I need to emit events from several different files.
In app.js:
var updates = require('updates.js');
setTimeout(function() {
updates.regular.on("update", function () {
console.log("Updated.");
})
}, 1000);
setTimeout(
function () {
console.log(updates.regular.eventNames()); // Verifying that there is actually a listener bound to the socket -> prints ['update']
updates.regular.emit("update", 100)
}, 1500);
In updates.js:
var io = require("socket.io");
var socket_8888 = io(8888);
var updates = {
regular: socket_8888
};
module.exports = updates;
However, a few simple tests have uncovered that events are not being handled, and I really cannot figure out why. The word "Updated" should print a second and a half after I run the application using "node www", but it does not.
The reason I started doing this simple testing was because I am trying to revive an old website of mine, but after a couple years, API updates have rendered a lot of my code useless. So I am trying to rebuild. I am not trying to send events between different files on the server. I am only testing the events locally because the events were not firing to the browser client. For this reason, I decided to investigate using this simple test, and it turns out the events can not even be emitted/listened to on the actual server, let alone be handled on a client that is on a whole different network.
I have already verified that the listener is actually binding to the socket. However, I do not know how to check whether or not the socket is actually emitting the event "update".
I have written the listener to bind only after one second because attempting to bind the moment the application starts does not give Express enough time to set everything up. Otherwise, the socket would still be undefined.
I do not get any error messages. The code just does not work as I expected.
I would really appreciate it if the community can tell me why the event 'update' is not being handled.
To include update module (update.js)
Try this
It work's Perfectly
module.exports = updates
var updates = require('./updates');
Related
I'm using ws version 7.4.0 and I would want to display a console log or perfom operations between the moment where the client is sending a message to the server and before the server fire the on event message.
To represent it:
webserver.on('example', function callback(msg){console.log(msg);}); //act before the call of callback
client------server---[here]---callback
The only way I see right now would be to use a "root" function before the callback of all my events like this:
function callback(msg){console.log(msg);}
webserver.on('example', function root(msg) {console.log('example msg'); callback(msg);});
I don't know if this is a real and/or good solution I really wish to write a clean and organized application.
If someone could give me some advise or a real solution? Thank you.
You could make a wrapper for all of your callbacks like so:
function makeCallback(fn) {
return function(msg) {
if (!environment.prod) console.log(msg);
fn(msg)
};
}
var myCallback = makeCallback(function (msg) {
// something
});
webserver.on('example', myCallback);
Or I think the better solution is to stream the requets into your stdout although I don't know the implications of using this method.
And I want to address the naming of your websocket server. Even though a web socket server is technically a web server, it only responds to the websocket protocol and naming it webserver could be misleading, I would recommend using the naming like in their documents wss.
I am using this (contentful-export) library in my express app like so
const app = require('express');
...
app.get('/export', (req, rex, next) => {
const contentfulExport = require('contentful-export');
const options = {
...
}
contentfulExport(options).then((result) => {
res.send(result);
});
})
now this does work, but the method takes a bit of time and sends status / progress messages to the node console, but I would like to keep the user updated also.. is there a way I can send the node console progress messages to the client??
This is my first time using node / express any help would be appreciated, I'm not sure if this already has an answer since im not entirely sure what to call it?
Looking of the documentation for contentful-export I don't think this is possible. The way this usually works in Node is that you have an object (contentfulExport in this case), you call a method on this object and the same object is also an EventEmitter. This way you'd get a hook to react to fired events.
// pseudo code
someLibrary.on('someEvent', (event) => { /* do something */ })
someLibrary.doLongRunningTask()
.then(/* ... */)
This is not documented for contentful-export so I assume that there is no way to hook into the log messages that are sent to the console.
Your question has another tricky angle though. In the code you shared you include a single endpoint (/export). If you would like to display updates or show some progress you'd probably need a second endpoint giving information about the progress of your long running task (which you can not access with contentful-export though).
The way this is usually handled is that you kick of a long running task via a certain HTTP endpoint and then use another endpoint that serves infos via polling or or a web socket connection.
Sorry that I can't give a proper solution but due to the limitation of contentful-export I don't think there is a clean/easy way to show progress of the exported data.
Hope that helps. :)
When I start my server, I get 1 response from the web socket that shows information about bitcoin but I either never get updates whenever the price changes or I suddenly get loads of updates. I assume I should be getting a new message every second or so. I'm using this web socket https://www.cryptocompare.com/api/#-api-web-socket-current-
Here's my code:
var ioClient = require('socket.io-client');
var cryptocompare = ioClient.connect('wss://streamer.cryptocompare.com')
var subscription = '2~Poloniex~BTC~USD';
cryptocompare.emit('SubAdd', { subs: [subscription] });
cryptocompare.on('error', console.error)
cryptocompare.on('m', function(message) {
console.log(message);
});
In the first instance I would very strongly encourage you to use the Tidwall websockets library
https://github.com/tidwall/SwiftWebSocket
It's incredibly well-written, it's one of the best libraries of any type out there.
Again in the first instance, you'll struggle to know what is going on, until you are using a rock-solid library ...
We need to update the client side UI to indicate that a message fails to deliver. How do I have Socket.IO JS client call a custom callback directly when the message fails to deliver? For example, something like:
socket.emit("event", data).onError(myCallback);
I know Socket.IO provides the Ack mechanism to confirm delivery success. Therefore, one can set up a timer with a handler which calls the failure callback, if the ack is not called after a certain amount of time. But this doesn't seem to be the best way to do.
Also there is the error event provided by Socket.IO, but it doesn't come with info regarding which emit caused the error.
Unfortunately there's no way to get errors from callbacks, the only way is to indeed create your own timeout:
var timeoutId = setTimeout(timeoutErrorFn, 500);
var acknCallbackFn = function(err, userData){
clearTimeout(timeoutId)
//manage UserData
}
socket.emit('getUserData', acknCallbackFn);
Source of the code
And there's another issue about this, open
So for the time being you have to stick with your manual setTimeout.
I'm trying to catch when a user leaves from my Meteor application (version 1.2.0.2) ; something equivalent to the SocketIO disconnect() on the server side.
The user could close his browser, go to another website or simply refresh the page and it would fire anyway
Surprisingly, i'm searching on Internet and everything is mixed up, nothing works properly. I thought Meteor was literally based on this magic-live processing so it must manage this event in a way or another.
Iron router documentation specify this :
onStop: Called when the route is stopped, typically right before a new
route is run.
I also found Router.load and Router.unload but none of them work. This is my current [not working] code which is quite simple
Router.configure
layoutTemplate: 'MasterLayout'
loadingTemplate: 'Loading'
notFoundTemplate: 'NotFound'
Router.onStop (->
console.log('Try to stop')
Users.insert({
name: "This is a test"
lat: 0
lng: 0
})
)
Am I doing something wrong here ? How do you catch this event in my app ?
You need to attach to the onStop of the route, not the router. For instance:
Router.route('/', {
onStop: function() {
console.log("someone left the '/' route");
}
});
Another option is to use the onStop event of subscriptions. That is probably the option most similar to the socketio disconnect you mentioned. You can find an example of that in the typhone source code.
There were two solution working, I found the 2nd and best one by searching in the API Documentation for a while.
First solution : working with subscribe & publish
Anywhere in the controller / front-end side you must subscribe to a collection
# in coffee
#subscribe('allTargets')
# in javascript
this.subscribe('allTargets')
Afterwards you just have to publish and add a onStop listener. This example will take a Targets collection I already defined somewhere before, it just gets all the entries.
# in coffee
Meteor.publish 'allTargets', ->
#onStop ->
# Do your stuff here
return Targets.find()
# in javascript
Meteor.publish('allTargets', function() {
this.onStop(function() {
// Do your stuff here
});
return Targets.find();
});
You have to be careful not to return Targets.find() before you set the onStop listener too. I don't think it's a perfect solution since you don't listen to the connection itself but the changes of a collection.
Second solution : working with DDP connection
I realized through the Meteor API Documentation we can directly listen to the connection and see if someone disconnect from the server-side.
To stay well-organized and clean within my Meteor Iron project I added a new file in app/server/connection.coffee and wrote this code
# in coffee
Meteor.onConnection (connection) ->
connection.onClose ->
# Do your stuff
# in javascript
Meteor.onConnection(function(connection) {
connection.onClose(function() {
// Do your stuff
});
});
You can manage datas with connection.id which's the unique identifier of your browser tab. Both solutions are working well for me.
If you use Meteor.userId through their accounts system, you can't use it outside a method in the server-side so I had to find a workaround with the connection.id.
If anyone has a better solution to manage connections while getting this kind of client datas, don't hesitate to give your input.