What are the advantages and disadvantages of using only socket based communication vs a hybrid of REST and socket (using socket only when bidirectional communication is necessary, like receiving messages in a chat).
When I say only socket, I mean that instead of sending a GET request asking for /entities, I'd send update_needed and the server would send a push via socket.
My question is not really about performance, it's more about the concept, like delegate vs block/lambda (using socket would be like the delegate concept and REST is more like block).
It all boils down to what type of application and level of scalability you have in mind.
WebSocket/REST: Client connections?
How to handle CQRS from a client-side perspective
Hard downsides of long polling?
The main reason why I wouldn't use WebSockets in any major project is simply that still many users don't use a modern browser that support them. Namely IE 8 and 9 don't support them and both together still have a market share of over 20 % (Oct 15).
Related
I've been working through a bunch of WebRTC examples, and they all require a custom Websocket server for exchanging the signalling data. OTOH, every WebRTC doc states that you can use anything for signalling, including carrier pidgeons.
So I've been wondering, just out of curiosity: why isn't signalling usually done using a boring old REST API (or similar)? It's not as if the setup process has realtime requirements, for which using Websockets would make sense...
Because you want the setup process to be as quick as possible—usually—and there can be quite a few messages to exchange, especially if you use ICE trickling. Using AJAX you'd have to use repeated polling, which is certainly slower. If that's good enough for you and you see some advantage in doing it that way vs. web sockets, more power to you. But typically you'd want to forward messages to the other peer as soon as you get them, not whenever the other peer happens to poll the server next. And the only practical option to push data from the server to the client are web sockets.
You could use server-sent events for the server-to-client push and AJAX for the client-to-server sending… but why, when web sockets already provide duplex communication?
I am working on an automation project using Raspberry pi and Windows IoT. Is it possible to broadcast to a web page, similar to Server-Send-Event? I am monitoring certain events and instead of calling server every few seconds for updates, I would like server to send the alert to web page direct. Any help would be greatly appreciated.
I think you can use WebSockets. WebSockets are an advanced technology that makes it possible to open an interactive communication session between the user's browser and a server. You can refer to this sample. Or you can use IoTWeb to embed a simple HTTP and WebSocket server into your application.
Update:
WebSockets are a great addition to the HTTP protocol suite, but there are numerous situations where they cannot be used.
Some companies have firewalls that will prevent WebSockets from
working.
If you are deploying software in a shared hosting
environment, you may not be permitted to use WebSockets.
If you are
behind a reverse proxy that isn’t configured or the software doesn’t
support pass-through of WebSocket protocol, WebSockets won’t work.
Another option is long polling,the browser does an XHR request and the server simply doesn’t respond until it has something to send. But in this way, if you want to do 2-way communications with the server, you are effectively using 2 sockets. One is tied up hanging/waiting for the long poll response, and the other is sent by the client to send new information to the server. Long polling is also problematic because the client has to be able to handle XHR errors, some of which are tricky to handle or even impossible to handle. You can search more differences and disadvantages from internet.
I'm building web app that needs to communicate with another application using socket connections. This is new territory for me, so want to be sure that sockets are different than websockets. It seems like they're only conceptually similar.
Asking because initially I'd planned on using Django as the foundation for my project, but in the SO post I linked to above it's made very clear that websockets aren't possible (or at least not reliable, even with something like django-websockets) using the preferred Django setup (Apache with mod_wsgi). Yet I've found other posts that casually import Python's socket module for something as simple as grabbing the server's hostname.
So:
Are they really different?
Is there any reason not to use Django for a project that relies on establishing socket connections with an outside server?
To answer your questions.
Even though they achieve (in general) similar things, yes, they are really different. WebSockets typically run from browsers connecting to Application Server over a protocol similar to HTTP that runs over TCP/IP. So they are primarily for Web Applications that require a permanent connection to its server. On the other hand, plain sockets are more powerful and generic. They run over TCP/IP but they are not restricted to browsers or HTTP protocol. They could be used to implement any kind of communication.
No. There is no reason.
Websockets use sockets in their implementation. Websockets are based on a standard protocol (now in final call, but not yet final) that defines a connection "handshake" and message "frame." The two sides go through the handshake procedure to mutually accept a connection and then use the standard message format ("frame") to pass messages back and forth.
I'm developing a framework that will allow you to communicate directly machine to machine with installed software. It might suit your purpose. You can follow my blog if you wish: http://highlevellogic.blogspot.com/2011/09/websocket-server-demonstration_26.html
WebSocket is just another application level protocol over TCP protocol, just like HTTP.
Some snippets < Spring in Action 4> quoted below, hope it can help you understand WebSocket better.
In its simplest form, a WebSocket is just a communication channel
between two applications (not necessarily a browser is
involved)...WebSocket communication can be used between any kinds of
applications, but the most common use of WebSocket is to facilitate
communication between a server application and a browser-based application.
You'd have to use WebSockets (or some similar protocol module e.g. as supported by the Flash plugin) because a normal browser application simply can't open a pure TCP socket.
The Socket.IO module available for node.js can help a lot, but note that it is not a pure WebSocket module in its own right.
It's actually a more generic communications module that can run on top of various other network protocols, including WebSockets, and Flash sockets.
Hence if you want to use Socket.IO on the server end you must also use their client code and objects. You can't easily make raw WebSocket connections to a socket.io server as you'd have to emulate their message protocol.
WebSocket is a computer communications transport protocol (like TCP, HTTP 1.0, HTTP 1.1, HTTP 2.0, QUIC, WebRTC, etc.)
Socket is an endpoint for sending and receiving data across the network (like Port number)
Example of Socket:
(TCP, 8.8.8.4, 8080, 8.8.8.8, 8070)
where:
(protocol, local address, local port, remote address, remote port)
Regarding your question (b), be aware that the Websocket specification hasn't been finalised. According to the W3C:
Implementors should be aware that this specification is not stable.
Personally I regard Websockets to be waaay too bleeding edge to use at present. Though I'll probably find them useful in a year or so.
We are building a proprietary system involving a client and a server linked over TCP/IP. Occasionally, the server will have some new expected or unexpected information that would be of interest to the client. My understanding is that SOAP and REST are query/response systems that require the client to request something and the server responds back. We need the client to register and the server to respond back if and when the new information is available. Are these protocols capable of such behavior? In addition, we need standard database-like queries requiring immediate response.
If you are in the Microsoft world, take a look at WCF, it is capable of this type of communication.
Whether you are in the Microsoft world or not, I would suggest looking into XMPP and AMQP.
First, REST isn't a protocol, it's more of an architecture style.
Second, neither of these are designed for push data delivery.
You could use either for the query-type messages, but you'll need to devise an out-of-band communication protocol to use for push notifications. If your data is fairly simple you could just use a basic TCP socket.
Closed. This question needs to be more focused. It is not currently accepting answers.
Want to improve this question? Update the question so it focuses on one problem only by editing this post.
Closed 4 years ago.
Improve this question
I'm looking to establish some kind of socket/COMET type functionality from my server(s) to my iPhone application. Essentially, anytime a user manages to set an arbitrary object 'dirty' on the server, by say, updating their Address.. the feedback should be pushed from the server to any clients keeping a live poll to the server. The buzzword for this is COMET I suppose. I know there is DWR out there for web browser applications, so I'm thinking, maybe it's best to set a hidden UIWebView in each of my controllers just so I can get out of the box COMET from their javascript framework? Is there a more elegant approach?
There are a couple of solutions available to use a STOMP client.
STOMP is incredibly simple and lightweight, perfect for the iPhone.
I used this one as my starting point, and found it very good. It has a few object allocation/memory leak problems, but once I got the hang of iPhone programming, these were easy to iron out.
Hope that helps!
Can you use ordinary TCP/IP socket in your application?
A) If yes then definitely a raw TCP/IP socket is more elegant solution. From your iPhone app you just wait for notification events. The socket is open as long as your application is open. If you want you can even use HTTP protocol / headers.
On the server side you can use some framework to write servers which efficiently handle thousands of open TCP/IP connections. e.g Twisted, EventMachine or libevent. Then just bind the server main socket to http port (80).
The idea is to use a server which keeps just a single data structure per client. Receives update event from some DB application and then pushes it to right client.
B) No, you have to use Apache and http client on iPhone side. Then you should know that whole COMET solution is in fact work around for limitations of HTTP protocol and Apache / PHP.
Apache was designed to handle many short time connections. As far I know only newest versions Apache (mpm worker) can handle efficiently big number of opened connection. Previously Apache was keeping one process per connection.
Web browsers have a limit of concurrent open connections to one web server (URL address in fact, eg. www.foo.com, not IP address of www.foo.com). And the limit is 2 connections. Additionally, a browser will allow only for AJAX connections to the same server from which the main HTML page was downloaded.
I wrote a web server for doing exactly this kind of thing. I'm pushing realtime updates through the server with long polling and, as an example, I had safari on the iPhone displaying that data.
A given instance of the server should be able to handle a few thousand concurrent clients without trying too hard. I've got a plan to put them in a hierarchy to allow for more horizontal scaling (should be quite trivial, but doesn't affect my current application).
WebSync has a javascript client that works on the iPhone, if that's what you're after
Would long-polling work for what you want to achieve? You can implement the client-side in a few lines of regular Javascript, which will be lighter than any framework could possibly be.
It would also be trivial to implement it in ObjC (connect, wait for a response or timeout, repeat)
The answers to my question Simple "Long Polling" example code? hopefully explain how extremely simple Long Polling is..
Basically you would just request a URL as usual - the web-server would accept the connection, but not send any data until it's available. When you receive data, or the connection times-out, you reconnect (and repeat)
The most complicated bit would be server server-side, as you cannot use a regular threaded web-server like Apache, although this is also the case with Comet..
StreamHub Comet Server works with the iPhone out of the box, no plugins or anything required. Just browsed to their website on my iPhone and all the examples worked, didn't need to install Flash or anything.
Do you want/have do the communication for your app over http? If not, you can use CFNetwork framework to use sockets (TCP/UDP) to allow your app and server to communicate. From what I have seen of the CFNetwork stack, it is pretty cool, and makes it fairly straitforward to read and write to streams, and allows for synchronous and asynchronous communication. It also allows for you to define callbacks on your socket allowing you to get notified of events like data received, connection made, etc. So, in your example you could send the information over the socket to your server, and then you could define a callback that would listen for incoming data on the stream and then update your app accordingly.
EDIT: Did a little more research, and if you go the socket approach, you may want to also look at the NSStream classes. They are Cocoa abstractions build on top of the CFSocket stuff.
you didn't mention what serverside tech you're using. But in case it's microsoft .net (or for any other googlers who come across this), there is a simple option for comet: http://www.codeplex.com/ncomet.
COMET, LightStreamer, AJAX all that junk is broken. It is basics of TCP that no 'keep-alives' are ever guaranteed without pinging traffic.. So you can forget that long-polling if any decent reliability or timely delivery is to be guaranteed..
It's just hype everyone saw through back in 2003 when the lame-mania kicked off..