&gt; How to Use Sockets in JavaScript/HTML?

There is no facility to use general-purpose sockets in JS or HTML. It would be a security disaster, for one.

There is WebSocket in HTML5. The client side is fairly trivial:

    socket= new WebSocket(&#39;ws://www.example.com:8000/somesocket&#39;);
    socket.onopen= function() {
        socket.send(&#39;hello&#39;);
    };
    socket.onmessage= function(s) {
        alert(&#39;got reply &#39;+s);
    };

You will need a specialised socket application on the server-side to take the connections and do something with them; it is not something you would normally be doing from a web server&#39;s scripting interface. However it is a [relatively simple protocol][2]; my noddy Python SocketServer-based endpoint was only a couple of pages of code.

In any case, it doesn&#39;t really exist, yet. Neither the JavaScript-side spec nor the network transport spec are nailed down, and no browsers support it.

You can, however, use Flash where available to provide your script with a fallback until WebSocket is widely available. Gimite&#39;s [web-socket-js][1] is one free example of such. However you are subject to the same limitations as Flash Sockets then, namely that your server has to be able to spit out a cross-domain policy on request to the socket port, and you will often have difficulties with proxies/firewalls. (Flash sockets are made directly; for someone without direct public IP access who can only get out of the network through an HTTP proxy, they won&#39;t work.)

Unless you really need low-latency two-way communication, you are better off sticking with `XMLHttpRequest` for now.

[1]: http://github.com/gimite/web-socket-js
[2]: https://datatracker.ietf.org/doc/html/draft-hixie-thewebsocketprotocol


Specifications:  

 - [Web Sockets API][1]

Articles:

 - [HTML5 WebSocket and WebJneering][2]

Tutorial:  

 - [HTML5 Rocks - WebSockets][3]

Libraries:  

 - Check this SO post [html5 websocket
   need server?][4], it links to
   https://kaazing.com/download


  [1]: https://html.spec.whatwg.org/multipage/web-sockets.html#network
  [2]: http://svwebbuilder.wordpress.com/2008/10/20/html5-websocket-and-webjneering/
  [3]: https://www.html5rocks.com/en/tutorials/websockets/basics/
  [4]: https://stackoverflow.com/questions/1530023/html5-websocket-need-server

I think it is important to mention, now that this question is over 1 year old, that [Socket.IO][1] has since come out and seems to be the primary way to work with sockets in the browser now; it is also compatible with [Node.js][2] as far as I know.


  [1]: http://socket.io/
  [2]: http://nodejs.org/

The logic is of the model is:  

 - A `Building` has many `Rooms`
 - A `Room` may be inside another `Room` (a closet, for instance--ForeignKey on &#39;self&#39;)  
 - A `Room` can only be inside another `Room` in the same building (this is the tricky part)  
  
Here&#39;s the code I have:  

    #spaces/models.py
    from django.db import models    
    
    class Building(models.Model):
        name=models.CharField(max_length=32)
        def __unicode__(self):
            return self.name

    class Room(models.Model):
        number=models.CharField(max_length=8)
        building=models.ForeignKey(Building)
        inside_room=models.ForeignKey(&#39;self&#39;,blank=True,null=True)
        def __unicode__(self):
            return self.number

and:

    #spaces/admin.py
    from ex.spaces.models import Building, Room
    from django.contrib import admin
    
    class RoomAdmin(admin.ModelAdmin):
        pass

    class RoomInline(admin.TabularInline):
        model = Room
        extra = 2

    class BuildingAdmin(admin.ModelAdmin):
        inlines=[RoomInline]

    admin.site.register(Building, BuildingAdmin)
    admin.site.register(Room)


The inline will display only rooms in the current building (which is what I want).  The problem, though, is that for the `inside_room` drop down, it displays all of the rooms in the Rooms table (including those in other buildings).


In the inline of `rooms`, I need to limit the `inside_room` choices to only `rooms` which are in the current `building` (the building record currently being altered by the main `BuildingAdmin` form). 


I can&#39;t figure out a way to do it with either a `limit_choices_to` in the model, nor can I figure out how exactly to override the admin&#39;s inline formset properly (I feel like I should be somehow create a custom inline form, pass the building_id of the main form to the custom inline, then limit the queryset for the field&#39;s choices based on that--but I just can&#39;t wrap my head around how to do it).

Maybe this is too complex for the admin site, but it seems like something that would be generally useful... 


Limit foreign key choices in select in an inline form in admin

I am new to Python, and I am familiar with implementations of [Multimaps][1] in [other][2] [languages][3]. Does Python have such a data structure built-in, or available in a commonly-used library?

To illustrate what I mean by &quot;multimap&quot;:

    a = multidict()
    a[1] = &#39;a&#39;
    a[1] = &#39;b&#39;
    a[2] = &#39;c&#39;

    print(a[1])  # prints: [&#39;a&#39;, &#39;b&#39;]
    print(a[2])  # prints: [&#39;c&#39;]

  [1]: http://en.wikipedia.org/wiki/Multimap
  [2]: http://www.sgi.com/tech/stl/Multimap.html
  [3]: http://docs.guava-libraries.googlecode.com/git/javadoc/com/google/common/collect/Multimap.html

Is there a &#39;multimap&#39; implementation in Python?

How to Use Sockets in JavaScript\HTML?

May be using some cool HTML5?

Libraries?
Tutorials?
Blog Articles?


How to Use Sockets in JavaScript\HTML?

How to Use Sockets in JavaScript\HTML?
May be using some cool HTML5?
Libraries?
Tutorials?
Blog Articles?

[JQuery](http://jquery.com/) has two versions for download, one is &lt;i&gt;Production (19KB, Minified and Gzipped)&lt;/i&gt;, and the other is _Development (120KB, Uncompressed Code)_.

Now the compact 19kb version, if you download it, you will see is still a javascript executable code. How did they compactify it? And how can I &#39;minify&#39; my code like that too?

How to &#39;minify&#39; Javascript code

Using `&amp;url=&#39;+encodeURIComponent(url);` to pass a URL from browser to server will encode the url but when it is decoded at the server, the parameters of url are interpreted as seperate parameters and not as part of the single url parameter.

What is the recommended way to pass urls as url parameters ?

What is the recommended way to pass urls as url parameters?

Using the following jQuery will get the RGB value of an element&#39;s background color:

    $(&#39;#selector&#39;).css(&#39;backgroundColor&#39;);

Is there a way to get the hex value rather than the RGB?

How to get hex color value rather than RGB value?

I want to offer the right version of a download.  The versions I have are:

 - 32-bit Windows
 - 64-bit Windows
 - Linux

Detecting Linux using the User Agent field is easy; but is it possible to reliably figure out if Windows is 32-bit or 64-bit?

Users might be using weird browsers - IE and Firefox are common, and we probably have an Opera user somewhere; maybe a Chrome user too.  I know that 64-bit Windows 7 ships with 32-bit and 64-bit versions of IE, and I&#39;d like to send them both the 64-bit version of my download.

(Edited to add: I know that I should provide all the options, and I will.  But [people don&#39;t read the options][1].  So I wanted to provide the right download by default, to improve usability.  Of course, while this is helpful if I get it right, it&#39;s extremely unhelpful if I get it wrong.  And from the answers so far, it doesn&#39;t look like there&#39;s a reliable way of doing this).



  [1]: http://www.joelonsoftware.com/uibook/chapters/fog0000000062.html

Detect 64-bit or 32-bit Windows from User Agent or Javascript?

If you have worked with JavaScript at any length you are aware that Internet&amp;nbsp;Explorer does not implement the ECMAScript function for Array.prototype.indexOf() [including Internet&amp;nbsp;Explorer&amp;nbsp;8]. It is not a huge problem, because you can extend the functionality on your page with the following code.

    Array.prototype.indexOf = function(obj, start) {
         for (var i = (start || 0), j = this.length; i &lt; j; i++) {
             if (this[i] === obj) { return i; }
         }
         return -1;
    }

When should I implement this?

Should I wrap it on all my pages with the following check, which checks if the prototype function exists and if not, go ahead and extend the Array prototype?

    if (!Array.prototype.indexOf) {

        // Implement function here

    }

Or do browser check and if it is Internet&amp;nbsp;Explorer then just implement it?

    //Pseudo-code

    if (browser == IE Style Browser) {

         // Implement function here

    }


How to fix Array indexOf() in JavaScript for Internet Explorer browsers

I want to float a `div` to center. Is it possible? `text-align: center` is not working in IE. 

Align a div to center

I am developing a mobile web application (for iPhone &amp; Android) with a local database (using html5 webstorage) so my app is still usable when the user is offline.

This is working perfectly, but I want to save the local data on a server. So I need to synchronize the local DB with a DB on a server. The synchronisation can only be one way, but in the future, I would like to synchronize it in the both way (server &lt;-&gt; local DB).

This requierement looks very common (or will be common in the future for mobile web app), but I can&#39;t find a library doing that.

I know google is doing that in their mobile web app (ex. gmail), and I found the [WSPL project][2] a google project but without source to download.


If I can&#39;t find a solution, I will create a library to do that, as one way sync doesn&#39;t look difficult, but I wonder if there are other solutions.


  [2]: http://ajaxian.com/archives/web-storage-portability-layer-abstract-on-top-of-html5-and-gears-storage

Best way to synchronize local HTML5 DB (WebSQL Storage, SQLite) with a server (2 way sync)

How to draw a dotted line with css?

I have a table with a colored background and I need to specify the padding between the table and it&#39;s content, I.E. cells.  
The table tag doesn&#39;t seem to accept a padding value.  
Firebug shows the table and tbody&#39;s layout with padding 0 but doesn&#39;t accept any value entered for them, so I guess they just don&#39;t have the padding property.  
But the thing is I want the same separation between cells than the top cells with the table top and the bottom cells with the table&#39;s bottom.  
Again, what I want is not cell-padding.

EDIT: Thanks, what I really needed, I realize now, was border-spacing, or its html equivalent, cellspacing.  
But for some reason, they don&#39;t do anything in the site I&#39;m working on.  
Both work great on a separate HTML, but in the site they don&#39;t.  
I thought it could be some style overwriting the property, but cellspacing and an inline border-spacing shouldn&#39;t get overwritten, right?  
(I use firefox )

EDIT 2: No, TD padding is NOT what I need. With TD padding, top and bottom paddings of adjacent cells sum up, so there&#39;s double the space (pad actually) between two cells than between the top cell and the table top border. I want to have exactly the same distance between them.

How do you specify table padding in CSS? ( table, not cell padding )

I&#39;m looking for a tool that will give me the proper generated source including DOM changes made by AJAX requests for input into W3&#39;s validator. I&#39;ve tried the following methods:


 1. 
[Web Developer Toolbar][1] - Generates invalid source according to the doc-type (e.g. it removes the self closing portion of tags). Loses the doctype portion of the page.
 2. [Firebug][2] - Fixes potential flaws in the source (e.g. unclosed tags). Also loses doctype portion of tags and injects the console which itself is invalid HTML.
 3. IE Developer Toolbar - Generates invalid source according to the doc-type (e.g. it makes all tags uppercase, against XHTML spec).
 4. Highlight + View Selection Source - Frequently difficult to get the entire page, also excludes doc-type.

Is there any program or add-on out there that will give me the exact current version of the source, without fixing or changing it in some way? So far, Firebug seems the best, but I worry it may fix some of my mistakes.

**Solution**

It turns out there is no exact solution to what I wanted as Justin explained. The best solution seems to be to validate the source inside of Firebug&#39;s console, even though it will contain some errors caused by Firebug. I&#39;d also like to thank Forgotten Semicolon for explaining why &quot;View Generated Source&quot; doesn&#39;t match the actual source. If I could mark 2 best answers, I would.

  [1]: https://addons.mozilla.org/en-US/firefox/addon/60 &quot;Web Developer Toolbar&quot;
  [2]: https://addons.mozilla.org/en-US/firefox/addon/1843

Best Way to View Generated Source of Webpage?

I would like to use WebSockets in my Windows Forms or WPF-application. Is there a .NET-control that is supporting WebSockets implemented yet? Or is there any open source project started about it?

An open source solution for a Java Client supporting WebSockets could also help me.

Is there a WebSocket client implemented for .NET?

I&#39;m trying to implement a C# web socket server, but its giving me a few troubles.
I&#39;m running a webserver(ASP.NET) to host the page with the javascript and the web socket server is implemented as a C# console application.

I&#39;m able to detect the connection attempt from the client (chrome running the javascript) and also to retrieve the handshake from the client. But the client doesn&#39;t seem to accept the handshake I&#39;m sending back (the `onopen` function on the web socket is never called).

I&#39;ve been reading the [The Web Socket protocol][1] and I can&#39;t see what I&#39;m doing wrong.
Heres a bit of the server code:

    Socket listener = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.IP);
    IPEndPoint ep = new IPEndPoint(IPAddress.Parse(&quot;127.0.0.1&quot;), 8181);
    listener.Bind(ep);
    listener.Listen(100);
    Console.WriteLine(&quot;Wainting for connection...&quot;);
    Socket socketForClient = listener.Accept();
    if (socketForClient.Connected)
    {
        Console.WriteLine(&quot;Client connected&quot;);
        NetworkStream networkStream = new NetworkStream(socketForClient);
        System.IO.StreamWriter streamWriter = new System.IO.StreamWriter(networkStream);
        System.IO.StreamReader streamReader = new System.IO.StreamReader(networkStream);
    
        //read handshake from client:
        Console.WriteLine(&quot;HANDSHAKING...&quot;);
        char[] shake = new char[255];
        streamReader.Read(shake, 0, 255);
    
        string handshake =
           &quot;HTTP/1.1 101 Web Socket Protocol Handshake\r\n&quot; +
           &quot;Upgrade: WebSocket\r\n&quot; +
           &quot;Connection: Upgrade\r\n&quot; +
           &quot;WebSocket-Origin: http://localhost:8080\r\n&quot; +
           &quot;WebSocket-Location: ws://localhost:8181\r\n&quot; +
           &quot;\r\n&quot;;
    
        streamWriter.Write(handshake);
        streamWriter.Flush();

I&#39;m running to web server on port 8080 and the web socket server on port 8181, both on my localhost.

I&#39;ve tried sending the handshake in different encodings (ASCII, bytes and Hex) but this doesn&#39;t seem to make a difference. The connection is never fully established.
The javascript looks like this:

    var ws;
    var host = &#39;ws://localhost:8181&#39;;
    debug(&quot;Connecting to &quot; + host + &quot; ...&quot;);
    try {
     ws = new WebSocket(host);
    } catch (err) {
     debug(err, &#39;error&#39;);
    }
    ws.onopen = function () {
     debug(&quot;connected...&quot;, &#39;success&#39;);
    };
    ws.onclose = function () {
     debug(&quot;Socket closed!&quot;, &#39;error&#39;);
    };
    ws.onmessage = function (evt) {
     debug(&#39;response: &#39; + evt, &#39;response&#39;);
    };

I&#39;m guessing that the error lies in the C# server as chrome is sending the information as it should, but as a said the `onopen` function is never called.

**So my question in short:**
Has any of you ever accomplished this - and if yes, how did you do it?
And of cause: Do you see any apparent errors in the code (hope thats not to much to ask)


  [1]: https://datatracker.ietf.org/doc/html/draft-hixie-thewebsocketprotocol-75

Websocket server: onopen function on the web socket is never called

I&#39;ve read about [WebSockets][1] and I wonder why browser couldn&#39;t simply open trivial TCP connection and communicate with server like any other desktop application. And why this communication is possible via websockets?

  [1]: http://en.wikipedia.org/wiki/Web_Sockets 

What is the fundamental difference between WebSockets and pure TCP?

I found this project: http://code.google.com/p/standalonewebsocketserver/ for a WebSocket server, but I need to implement a WebSocket client in python, more exactly I need to receive some commands from XMPP in my WebSocket server.

Is there a WebSocket client implemented for Python?

I&#39;m looking for a websocket/node.js chat implementation which supports multiple rooms.

I&#39;m also going to write an app which needs multiple rooms or servers, and I&#39;m just looking for some code samples of how people do it.

Thanks.

I know there&#39;s a service http://pusherapp.com which provides this service, but I&#39;m looking for an open source example.

Content Type	Original Author	Original Content on Stackoverflow
Question	Rella	View Question on Stackoverflow
Solution 1 - Javascript	bobince	View Answer on Stackoverflow
Solution 2 - Javascript	o.k.w	View Answer on Stackoverflow
Solution 3 - Javascript	Ricket	View Answer on Stackoverflow

How to Use Sockets in JavaScript\HTML?

Javascript Problem Overview

Javascript Solutions

Solution 1 - Javascript

Solution 2 - Javascript

Solution 3 - Javascript

Is there a 'multimap' implementation in Python?

Limit foreign key choices in select in an inline form in admin

Attributions