It sounds like what you&#39;re waiting for is [WebRTC][1] which is working it&#39;s way through the standards process.  WebSockets, as other people have pointed out, run over TCP as a result of initiating with an HTTP Upgrade.


  [1]: http://www.webrtc.org/

No, it&#39;s not possible to have UDP communication within JavaScript. Sorry.

Sounds like the question is meant for client-side UDP, but since I ended up here...

You can do UDP in JavaScript on the server using the [node.js](http://nodejs.org/) [`dgram` package](http://nodejs.org/api/dgram.html#dgram_udp_datagram_sockets).

The WebSockets protocol is over TCP only as currently defined.

You could do [UDP with Flash](https://stackoverflow.com/questions/907041/is-it-possible-to-use-udp-in-flash-actionscript) if you are willing to use a RTMFP (Real Time Messaging Flow Protocol) server.


If this question is still pending:
I found a project called JNEXT and there is an example using UDP.
The project itself seems to be paused but at least in Firefox it works (it doesn&#39;t work with Chrome and Opera).
May be it is worth to look for it.


I think you can leverage Silverliht 4 technology. You can create a Silverlight 4 application to communicate with server and then enbamdded it to html page. Then your JavaScript can build TCP connections via Silverlight 4 application!

You could write a WebSocket server to serve as proxy/bridge between TCP/UDP.



I have a data set asking a customer how many pets they have for example. Is there a way with one query I can count the distinct values (1,2,3, etc)?
Thanks!

    +----------+------+
    | Customer | Pets |
    +----------+------+
    |       20 |    2 |
    |       21 |    3 |
    |       22 |    3 |
    |       23 |    2 |
    |       24 |    4 |
    +----------+------+

What I want is a list saying:

- 2 had 2 Pets
- 2 had 3 Pets
- 1 had 4 Pets

Count distinct values

How can I get the ascii character of a given ascii code.

e.g. I&#39;m looking for a method that given the code 65 would return &quot;A&quot;.


Thanks

How to get character for a given ascii value

I&#39;m writing a JavaScript Application that has to receive a huge amount of data from other users. It is not important if some of this data gets lost. Is there some way of using JavaScript WebSockets with UDP instead of TCP?

JavaScript WebSockets with UDP?

<p>I'm writing a JavaScript Application that has to receive a huge amount of data from other users. It is not important if some of this data gets lost. Is there some way of using JavaScript WebSockets with UDP instead of TCP?</p>


Suppose I have one div in my page. how to detect the user click on div content or outside of div content through JavaScript or JQuery. please help with small code snippet.
thanks.

**Edit**: As commented in one of the answers below, I only want to attach an event handler to my body, and also want to know which element was clicked upon.

Detect click inside/outside of element with single event handler

I am trying to use Jasmine to write some BDD specs for basic jQuery AJAX requests. I am currently using Jasmine in standalone mode (i.e. through `SpecRunner.html`). I have configured SpecRunner to load jquery and other .js files. Any ideas why the following doesn&#39;t work? has_returned does not become true, even thought the &quot;yuppi!&quot; alert shows up fine.

    describe(&quot;A jQuery ajax request should be able to fetch...&quot;, function() {
    
      it(&quot;an XML file from the filesystem&quot;, function() {
        $.ajax_get_xml_request = { has_returned : false };  
        // initiating the AJAX request
        $.ajax({ type: &quot;GET&quot;, url: &quot;addressbook_files/addressbookxml.xml&quot;, dataType: &quot;xml&quot;,
                 success: function(xml) { alert(&quot;yuppi!&quot;); $.ajax_get_xml_request.has_returned = true; } }); 
        // waiting for has_returned to become true (timeout: 3s)
        waitsFor(function() { $.ajax_get_xml_request.has_returned; }, &quot;the JQuery AJAX GET to return&quot;, 3000);
        // TODO: other tests might check size of XML file, whether it is valid XML
        expect($.ajax_get_xml_request.has_returned).toEqual(true);
      }); 
    
    });

How do I test that the callback has been called? Any pointers to blogs/material related to testing async jQuery with Jasmine will be greatly appreciated.


How do I verify jQuery AJAX events with Jasmine?

I would like to measure a time (in seconds in integers or minutes in floats) a user spends on a page. I know there is an unload event which I can trigger when they leave the page. But how to get a time they have already spent there?

How to measure a time spent on a page?

Is it possible to set width or height of HTML element (ex. `&lt;div&gt;`) in JavaScript in Standards Mode?

Note the following code:

    &lt;html&gt;
    &lt;script language=&quot;javascript&quot; type=&quot;text/javascript&quot;&gt;
        function changeWidth(){
            var e1 = document.getElementById(&quot;e1&quot;);
            e1.style.width = 400;
        } 
    &lt;/script&gt;
    &lt;body&gt;
        &lt;input type=&quot;button&quot; value=&quot;change width&quot; onclick=&quot;changeWidth()&quot;/&gt;
        &lt;div id=&quot;e1&quot; style=&quot;width:20px;height:20px; background-color:#096&quot;&gt;&lt;/div&gt;
    &lt;/body&gt;
    &lt;/html&gt;

When user presses the _change width_ button, the `&lt;div&gt;`&#39;s width should change.

It works fine when doctype declaration determines Quirks Mode. In Standards Mode I&#39;m unable to change the element&#39;s size this way

Is it possible to manipulate the size of an element in Standards Mode? How to bypass this disfunctionality?


Set element width or height in Standards Mode

What is the standard behavior for when a `&lt;button&gt;` element is clicked in a form? Will it submit the form?

Question is about tag/element `&lt;button&gt;`, not `&lt;input type=button&gt;`.

What&#39;s standard behavior when &lt;button&gt; element is clicked? Will it submit the form?

Is there a way to quickly bind to a TCP port/ip address and simply print out all information to STDOUT? I have a simple debugging solution which writes things to 127.0.0.1:4444 and I&#39;d like to be able to simply bind up a port from bash and print everything that comes across. Is there an easy way to do this?

Simple Socket Server in Bash?

I am using `tcpdump` to get HTTP data by executing the below command:   

    sudo tcpdump -A -s 1492 dst port 80

The result of above command:  

1. Headers, I think request and response headers.    
2. Unreadable data.   
3. The url `GET /modules/mod_news_pro_gk1/cache/stories.ilbalad.ajayeb.strange-tractor.jpg`.  

I need a more clear result, for example, readable request &gt; response header &gt; response body etc.
How can I filter my results?  

Can I use tcpdump to get HTTP requests, response header and response body?

I&#39;m looking for a quick and simple method for properly testing if a given TCP port is open on a remote server, from inside a Shell script.

I&#39;ve managed to do it with the telnet command, and it works fine when the port is opened, but it doesn&#39;t seem to timeout when it&#39;s not and just hangs there...

Here&#39;s a sample:

    l_TELNET=`echo &quot;quit&quot; | telnet $SERVER $PORT | grep &quot;Escape character is&quot;`
    if [ &quot;$?&quot; -ne 0 ]; then
      echo &quot;Connection to $SERVER on port $PORT failed&quot;
      exit 1
    else
      echo &quot;Connection to $SERVER on port $PORT succeeded&quot;
      exit 0
    fi


I either need a better way, or a way to force telnet to timeout if it doesn&#39;t connect in under 8 seconds for example, and return something I can catch in Shell (return code, or string in stdout).

I know of the Perl method, which uses the IO::Socket::INET module and wrote a successful script that tests a port, but would rather like to avoid using Perl if possible.

Note: This is what my server is running (where I need to run this from)

SunOS 5.10 Generic_139556-08 i86pc i386 i86pc

Test if remote TCP port is open from a shell script

I know the difference between the two on a technical level.

But in real life, can anyone provide examples (the more the better) of applications (uses) of TCP and UDP to demonstrate the difference?

What are examples of TCP and UDP in real life?

When, exactly, does the BSD socket `send()` function return to the caller?

In _non-blocking mode_, it should return immediately, correct?

As for _blocking_ mode, the [man page](http://manpages.ubuntu.com/manpages/lucid/man2/send.2.html) says:

&gt;When  the  message  does  not  fit  into the send buffer of the socket, **send()** normally blocks, unless the  socket  has  been  placed  in  non-blocking  I/O  mode.

Questions:

1. Does this mean that the `send()` call will always return immediately if there is room in the kernel send buffer?
2. Is the behavior and performance of the `send()` call identical for TCP and UDP? If not, why not?


Blocking sockets: when, exactly, does &quot;send()&quot; return?

What is the difference between TCP and UDP? 

I know that TCP is used in the case of non-time critical applications, and UDP is used for games or applications that require fast transmission of data. I know that TCP is used for HTTP, HTTPs, FTP, SMTP, and Telnet. I know that UDP is used for DNS and DHCP.

But why? What characteristics of TCP and UDP make it useful for their respective use cases? 

Difference between TCP and UDP?

I just came home from my exam in network-programming, and one of the question they asked us was **&quot;If you are going to stream video, would you use TCP or UDP? Give an explanation for both stored video and live video-streams&quot;**. To this question they simply expected a short answer of TCP for stored video and UDP for live video, but I thought about this on my way home, and is it necessarily better to use UDP for streaming live video? I mean, if you have the bandwidth for it, and say you are streaming a soccer match, or concert for that matter, do you really need to use UDP?

Lets say that while you are streaming this concert or whatever using TCP you start losing packets (something bad happened in some network between you and the sender), and for a whole minute you don&#39;t get any packets. The video-stream will pause, and after the minute is gone packets start to get through again (IP found a new route for you). What would then happen is that TCP would retransmit the minute you lost and continue sending you the live stream. As an assumption the bandwidth is higher than the bit-rate on the stream, and the ping is not too high, so in a short amount of time, the one minute you lost will act as a buffer for the stream for you, that way, if packet-loss happens again, you won&#39;t notice.

Now, I can think of some appliances where this wouldn&#39;t be a good idea, like for instance video-conferences, where you **need** to always be at the end of the stream, because delay during a video-chat is just horrible, but during a soccer-match, or a concert what does it matter if you are a single minute behind the stream? Plus, you are guaranteed that you get all the data and it would be better to save for later viewing when it&#39;s coming in without any errors.

So this brings me to my question. Are there any drawbacks that I don&#39;t know of about using TCP for live-streaming? Or should it really be, that if you have the bandwidth for it you should go for TCP given that it is &quot;nicer&quot; to the network (flow-control)?

TCP vs UDP on video stream

First of all, is there any problem with using both UDP and TCP on the same server?

Secondly, can I use the same port number?

Can TCP and UDP sockets use the same port?

I am playing around with HTML5 WebSockets. I was wondering, how do I close the connection gracefully? Like, what happens if user refreshes the page, or just closes the browser?

There is a weird behavior when a user just refresh the page without calling `websocket.close()` - when they return after the refresh it will hit the `websocket.onclose` event.

Closing WebSocket correctly (HTML5, Javascript)

I am curious if anyone has any information about the scalability of HTML WebSockets. For everything I&#39;ve read it appears that every client will maintain an open line of communication with the server. I&#39;m just wondering how that scales and how many open WebSocket connections a server can handle. Maybe leaving those connections open isn&#39;t a problem in reality, but it feels like it is.

Do HTML WebSockets maintain an open connection for each client? Does this scale?

[Socket.IO][1] seems to be the most popular and active WebSocket emulation library. [Juggernaut][2] uses it to create a complete pub/sub system.

[Faye][3] is also popular and active, and has its own javascript library, making its complete functionality comparable to Juggernaut. Juggernaut uses node for its server, and Faye can use either node or rack. Juggernaut uses Redis for persistence (**correction:** it uses Redis for pub/sub), and Faye only keeps state in memory.

1. Is everything above accurate?
2. Faye says it implements [Bayeux][4] -- i think Juggernaut does not do this -- is that because Juggernaut is lower level (IE, I can implement Bayeux using Juggernaut)
3. Could Faye switch to using the Socket.IO browser javascript library if it wanted to? Or do their javascript libraries do fundamentally different things?
4. Are there any other architectural/design/philosophy differences between the projects?


  [1]: http://socket.io/
  [2]: https://github.com/maccman/juggernaut
  [3]: http://faye.jcoglan.com/
  [4]: http://svn.cometd.com/trunk/bayeux/bayeux.html

Faye vs. Socket.IO (and Juggernaut)

I&#39;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 &lt;a href=&quot;https://stackoverflow.com/questions/152457/what-is-the-difference-between-a-port-and-a-socket&quot;&gt;sockets&lt;/a&gt; are different than &lt;a href=&quot;https://stackoverflow.com/questions/4363899/making-moves-w-websockets-and-python-django-twisted&quot;&gt;websockets&lt;/a&gt;.  It seems like they&#39;re only conceptually similar.  

Asking because initially I&#39;d planned on using Django as the foundation for my project, but in the SO post I linked to above it&#39;s made very clear that websockets aren&#39;t possible (or at least not reliable, even with something like django-websockets) using the preferred Django setup (Apache with mod_wsgi).  Yet I&#39;ve found other posts that casually import Python&#39;s socket module for something as simple as &lt;a href=&quot;https://stackoverflow.com/questions/4093999/how-to-use-django-to-get-the-name-for-the-host-server&quot;&gt;grabbing the server&#39;s hostname&lt;/a&gt;.

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? 

Difference between socket and websocket?

Both [WebSockets][1] and [Server-Sent Events][2] are capable of pushing data to browsers. To me they seem to be competing technologies. What is the difference between them? When would you choose one over the other?


  [1]: http://dev.w3.org/html5/websockets/
  [2]: https://html.spec.whatwg.org/multipage/server-sent-events.html#server-sent-events

WebSockets vs. Server-Sent events/EventSource

I am working on a websocket implementation and do not know what the sense of a mask is in a frame.

Could somebody explain me what it does and why it is recommend?

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-------+-+-------------+-------------------------------+
     |F|R|R|R| opcode|M| Payload len |    Extended payload length    |
     |I|S|S|S|  (4)  |A|     (7)     |             (16/64)           |
     |N|V|V|V|       |S|             |   (if payload len==126/127)   |
     | |1|2|3|       |K|             |                               |
     +-+-+-+-+-------+-+-------------+ - - - - - - - - - - - - - - - +
     |     Extended payload length continued, if payload len == 127  |
     + - - - - - - - - - - - - - - - +-------------------------------+
     |                               |Masking-key, if MASK set to 1  |
     +-------------------------------+-------------------------------+
     | Masking-key (continued)       |          Payload Data         |
     +-------------------------------- - - - - - - - - - - - - - - - +
     :                     Payload Data continued ...                :
     + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - +
     |                     Payload Data continued ...                |
     +---------------------------------------------------------------+


Content Type	Original Author	Original Content on Stackoverflow
Question	user142019	View Question on Stackoverflow
Solution 1 - Javascript	Chad	View Answer on Stackoverflow
Solution 2 - Javascript	Pablo Santa Cruz	View Answer on Stackoverflow
Solution 3 - Javascript	Nick Benes	View Answer on Stackoverflow
Solution 4 - Javascript	kanaka	View Answer on Stackoverflow
Solution 5 - Javascript	Klaus	View Answer on Stackoverflow
Solution 6 - Javascript	John	View Answer on Stackoverflow
Solution 7 - Javascript	Tim R.	View Answer on Stackoverflow

JavaScript WebSockets with UDP?

Javascript Problem Overview

Javascript Solutions

Solution 1 - Javascript

Solution 2 - Javascript

Solution 3 - Javascript

Solution 4 - Javascript

Solution 5 - Javascript

Solution 6 - Javascript

Solution 7 - Javascript

How to get character for a given ascii value

Count distinct values

Attributions