As Websockets are not allways implemented nowadays, some libraries try to circumvent this with the Flash plugin for example. However, that is not always available, and there are Websocket-like features with Ajax connections in frameworks too. However, is there an Websocket standard conforming abstraction library that provides a reliable Websocket in any cases? Eg. cross-browser, firewall safe etc.?
Socket.IO is probably the closest thing. There is a primary server implementation in Node.js but Socket.IO can also be thought of as a higher level protocol layer that can use various transports underneath (with WebSockets being preferred) and as such there are other implementations of Socket.IO servers in other languages.
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Is there a reason why HTTP2 is required when websocket is already available?
Nathan Aw (Singapore)
Why do we need HTTP/2 when we have WebSockets? Well why did we need WebSockets when we have TCP? Or even IP? Protocols are basically agreed standards that can be implemented by independent parties.
WebSockets are good for two way communication but are mostly unstructured on top of that and application specific. HTTP is (mostly) a series of one-way requests to the server (ask for a resource, receive an answer) — though HTTP/2 enhances that slightly with HTTP/2 push and the binary framing layer could in theory be used more for proper two way push. So the full two way nature of WebSockets — the very thing they are good at — is not really needed for most HTTP use cases.
Looking at HTTP, it has various extras that WebSockets does not have. Including defined methods, headers and compression. This allows a well-defined understanding between various HTTP implementations to facilitate communications for its use case including features like multiplexing, caching, compression, redirects, error handling... etc. If you had to reinvent all of those on top of WebSockets (which is a very raw protocol), you’d end up with an HTTP/2 like protocol.
Could HTTP/2 have used WebSockets to act as it’s underlying transport layer? Possibly, but that’s an unnecessary extra level of abstraction (IP->TCP->WS->HTTP2->HTTP), not to mention that websockets are often established over HTTP initially. HTTP is big enough to have its own transport protocol so in fact they’ve gone the other way and specified WebSockets over HTTP/2.
Finally, it should also be noted that HTTP/2 does not make Web Sockets obselete either. They are different and with different advantages and disadvantages.
I am working on a project which involves real time chat (messaging, including group chats).
I have worked with websockets before, So I started working on this using spring-websockets and I did some reading about what is the best way to implement it. Then I came across STOMP (as a sub-protocol for websockets)and as there is direct support for STOMP in spring it was bit easy to achieve what I was supposed to do.
But my doubt is as far as my understanding STOMP and XMPP are similar protocols(messaging protocols) but I could not find any questions/blogs where the differences are explained and why somebody would prefer one over another?
It will be really helpful if somebody explains how these two protocols differ?
Thank you.
As the successor of Jabber, XMPP is more focused on instant messaging instead of STOMP. XMPP is an extensible protocol and could be used for other purposes, but there are plenty of built-in mechanism and implementations regarding IM. STOMP offers a more general mechanism and "message" here refers a broad meaning.
Let's say you choose STOMP for your project. Then you will probably need to define basic messages for certain scenarios (peer-to-peer, group chat) which are already offered by XMPP.
To compare two protocols;
STOMP message is carried as plain text (as its name indicates) whereas XMPP is structured as XML.
STOMP connections can be established via TCP or WebSockets. XMPP supports TCP or HTTP (WebSocket standard is also propopsed).
In Java world, Spring has the ability to talk STOMP and it's very easy to implement. However, XMPP support can be added by adding 3rd Party APIs (i.e. Smack)
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 had a huge confusion in WebSockets. I read some blog about WebSockets and it requires node websocket server, I downloaded the demo files and the chat application didn't seem to work. To summarize this, what do I need to use WebSockets? Do I need to download node server or something? And what is something to relate with socket.io to one another?
WebSockets?
WebSockets is a standard for implementing socket communication (to a server) over the web.
Is node required?
Now this server which the socket communication prevails between can be implemented in any way whatsoever. Node is surely a popular option to implement the server side in however its not the only, you can use python, erlang, ruby, or any other language where you can bind a socket connection.
What is socket.io?
socket.io is javascript library which makes it possible for socket OR socket-like connections over the web. See the WebSockets is a recent standard, not all browsers support it, only the modern ones do (proof: http://caniuse.com/#search=websockets). What makes socket.io so popular, rainbow and fairy tale like (and one of the main reasons why you happened to stumble upon it while researching WebSockets) is that it will make socket/socket-like communications possible in all browsers.
socket: when socket.io detects a browser supporting WebSockets, in which case it uses this WebSockets implementation for the socket communications.
socket-like: however when socket.io detects a browser which does NOT support WebSockets it will still provide you with socket-like communication. Tid bit: the internals of this feature use AJAX polling.
Node is a good place to start for websockets, but by no means the only place.
I would probably start here:
http://www.html5rocks.com/en/tutorials/websockets/basics/
I was doing AJAX implementation and would like to use Websocket when the client web browser supports it. Is there any frameworks that supports Websocket but falls-back to other methods when it detects the client side doesn't support Websocket.
There is also Atmosphere
http://atmosphere.dev.java.net
which support both client and server.
Yes sort of see www.kaazing.org
Kaazing Gateway supports all major browsers (Firefox version 1.5 and higher, Internet Explorer version 5.5 and higher, Safari version 3.0 and higher, Opera version 9.5 and higher, and Google Chrome version 0.2 and higher).
Socket.io is designed for this.
http://socket.io/
It is purely javascript that tries several different transport methods including XHR long-polling, WebSocket and FlashSocket amongst others.
You could also use Nirvana from www.my-channels.com.
When WebSocket is not supported it will fall back to a Comet based approach transparently.
Of course, you could try using jWebSocket, it is a pure Java/JavaScript high speed bidirectional communication solution for the Web - secure, reliable and fast. jWebSocket is provided to you to create innovative HTML5 based streaming and communication applications on the web. HTML5 WebSockets will replace the existing XHR approaches as well as Comet services by a new flexible and ultra high speed bidirectional TCP socket communication technology. jWebSocket is an open source Java and JavaScript implementation of the HTML5 WebSocket protocol with a huge set of extensions. Some demos or examples can be seen for you in the website, you can visit it here: https://jwebsocket.org/