I learned the hard way that the browsers' WebSocket API does not support back-pressure. Is there a way to work around this limitation without having to manually implement control flow on the application layer protocol? Would it for example be possible to implement a full WebSocket client in WASM, instead of having to proxy everything through the browser's API?
Back-pressure: no changes to the protocol that are addressing this issue are published to this time.
WebAssembly: there is no access to the WebSocket API (or any other) at this time from a pure WebAssembly module. You will have to use JavaScript in one way or another.
Related
I am working on a project which is basically a Customer Feedback Analysis Dashboard. There are few graphs on the dashboard and data for each graph is fetched from the server through API requests.
Right now the dashboard is updated every time the page is refreshed. I want it to be updated immediately when there is a new feedback in the system. I am confused, whether I use websockets to send data for each graph or just a flag and use that flag to fetch data through API requests.
Like, facebook/twitter does. They tell you about new posts/tweets and when you click that button your feed/wall gets updated.
If you want to "push" data from server to client and you want that data to show up in a timely fashion (e.g. within 10-20 seconds of when it was available on the server), then you will want to implement some sort of "push" solution where the server can efficiently push data to the client whenever there is new data to send.
There are several possible approaches:
webSockets
socket.io
Server-sent events
Mobile platform-specific push (Android and iOS)
For a general purpose solution that works within a browser, you will want to use one of the first three. socket.io is built on top of webSockets (it just adds more features) so architecturally, they are similar.
Server-sent events are fairly new (modern browsers only) and are only for one way communication (from server to client). webSockets can be used for communication either way.
I'd personally recommend socket.io because of the features it offers (such as automatic client reconnection) and a simplified messaging layer. You can see the feature difference between socket.io and webSockets here. With socket.io, the client makes a connection to the server when the web page is loaded and that connection is persistent. After the connection is established, then either client or server can send messages to the other at any time in a very efficient manner.
Other useful references:
Push notification | is websocket mandatory?
websocket vs rest API for real time data?
Why to use websocket and what is the advantage of using it?
What are the pitfalls of using Websockets in place of RESTful HTTP?
Ajax vs Socket.io
I built a realtime application that, thanks to Socket.IO, can serve a lot of different client types (C#, Java, Browser, ...)! I know that there are a lot of Socket.IO alternatives, but from my understanding, everything is more or less based on WebSockets. (I know that Socket.IO has fallbacks if WebSockets are not working, but that they are more less "inferior workarounds" so to speak...)
My question is: Is there any comparable real-time engine available that is NOT based on WebSockets, but can still serve all those different clients?
You don't say what your endpoints are. If one of the endpoints is a browser with purely the built-in capabilities of the browser and Javascript, then a webSocket is your only way to get a continuous connection from the browser to some other destination.
If a webSocket is not supported (in an older browser), then the other socket.io fallbacks (such as xhr-long-polling) are the next best alternatives. As the browser has limited communication capabilities, if you can't use a webSocket, then an ajax call is your only other generally supported option without requiring plug-ins on each browser (such as Flash or Java or something like that). socket.io already supports the next-best options that are available in a browser - you can't do better than that if you're talking about a standard browser with no custom plug-ins.
If your endpoints don't necessarily include a browser and you can use any language or library you want, then you can use plain TCP sockets and then use whatever protocol you want over a TCP socket.
The WebSocket protocol establishes a bidirectional communication channel between server and client; they kind of speak more naturally with each other. The server can just send something to the client and the other way around. In http it just goes in one direction, there's a request and a response and everything needs to be initiated with a request from the client.
From my experience, realtime webApps like a multiplayer game or a chat become easier to develop and it apparently creates less overhead than using http - but still you can do the same things more or less elegant with http as well (see e.g. long polling).
Look at gmail or other existing webApps, they all use http (so does Socket.io as a fallback) and it works quite well.
I am searching for a server push technology for my web application.
I would like to use a similar technology as StackOverflow, as that one is working very well.
So, are there any suggestions?
For server-to-client push Server-Sent Events is a better choice than WebSockets. GitHub uses SSE for automatically showing new comments, pull requests, etc.
SSE is HTTP-compatible, so it will work with proxy servers and you won't need HTTPS to have it working in practice (e.g. plenty of mobile operators have a HTTP proxy that breaks unencrypted WebSockets, but SSE works fine).
SSE connection is lightweight and quick. There's no extra handshake and connection upgrade procedure. If you have SSE on every page, then your server will have less work to do.
SSE protocol is super simple. You don't need special web server or library for it, and it can be polyfilled for old browsers.
I suggest you have a look at QWebSockets, if you control the server-side.
Otherwise, socket.io is a good candidate.
There are also ghosted services like Pusher and PubNub, which are free for a moderate number of push messages.
Need to be able to continuously receive calls when a Chrome webpage is open. How do I do that even for users who are inside a strict enterprise network?
WebSockets? (but there's the proxy problems that doesn't know what wss:// is)
HTTP? (but will I have to poll?)
Other?
Since you included the "vLine" tag, I'll reply with some information on how our WebRTC platform will behave in an enterprise network. vline.js will use a secure WebSocket by default if the browser supports it and fall back to HTTPS long polling. As described here, the secure WebSocket may work depending on the exact proxy configuration. Feel free to test it out by using GitTogether or creating your own vLine service for testing.
I'm trying to develop an extension that detects every connection made by the browser to figure out the URLs being accessed. I know that this is possible via writing an HTTP/SOCKS proxy and configuring the browser to flow traffic via that. However, that's kind of overkill for the application that I'm trying to develop and it's best done as a Firefox Add-on if that's possible. Any clues/pointers would be highly appreciated.
Use nsIHttpActivityDistributor and there is many information about the http transaction and socket transport through observeActivity callback.
Read the official documentation https://developer.mozilla.org/en/Monitoring_HTTP_activity.