Server to browser communications

Discussion in 'JavaScript' started by astrazone, Aug 10, 2011.

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  1. #1
    I was wondering how to make the server send events to the browser(client) when database is updated?
    Google and facebook have it with their chat systems but I couldn't really understand how they work because after the page was sent, the connection is terminated.

    So how can I set up something that will receive data on database update?

    Thanks in advance,
    Astrazone
     
    astrazone, Aug 10, 2011 IP
  2. Cash Nebula

    Cash Nebula Peon

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    #2
    The client may be polling the server at regular intervals and checking for new data.
     
    Cash Nebula, Aug 10, 2011 IP
  3. astrazone

    astrazone Member

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    #3
    Lets think about it for a sec... Facebook has 750,000,000 users and 50% are active all the time, so its 375,000,000 users that need to send a request about every second no server in the world can handle it, 22500000000 requests per minute.
    And I read about it somewhere that they are using something that can receive data from the server like this http://dev.w3.org/html5/eventsource/.
    Did anyone ever used it? because I cant understand what do I need to use it.

    Update : I also found this, but I have no idea how to set it up and what do I need for it. looking for good advice about all of this
     
    astrazone, Aug 10, 2011 IP
  4. JohnnySchultz

    JohnnySchultz Peon

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    #4

    Yes, your right that can't be handled by a single server but Facebook has multiple servers, each server handle requests on a certain number of users. That's why it can handle those millions of users.

    On to your first question, checking database statuses like in chat are constantly checked with a certain interval. Sometimes this checking is done using Flash instead of Javascript intervals because it takes a big load to the browser. Flash will then call a certain javascript function to tell the browser that there's an update in the chat.
     
    JohnnySchultz, Aug 11, 2011 IP
  5. astrazone

    astrazone Member

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    #5
    I think that I am more interested in something like WebSync or CometD.
    But I dont know how to install CometD and the instructions aren't helping...
     
    astrazone, Aug 11, 2011 IP
  6. Farbyte

    Farbyte Member

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    #6
    The only way to do this from server side is to allow connections from the server to the client and have a port listening on the client.
    This would require opening firewalls etc.
     
    Farbyte, Aug 11, 2011 IP
  7. astrazone

    astrazone Member

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    #7
    I agree with you Farbyte, but I think that a server application would be faster than simply doing an AJAX request every second. I just need a simple guide on how to set it up on my server/XAMPP.
     
    astrazone, Aug 11, 2011 IP