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  1. #1
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    Is Bluetooth scatter-net possible ?

    Well from here I learnt that Bluetooth works in three modes single slave operation, a multi-slave operation and a scatternet operation.

    • I was wondering if I use scatternet will this increase the range of Bluetooth from 10mts/30ft to the area where the phones are scattered or spread?
    • Does Java ME support scatternet operation?
    • Is there any test code that I can view and understand on this forum/discussion board using scatternet?

  2. #2
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    Does this or that help?

    The specification might be able to that, however, real implementations of today still have problems with multi-slave sceanrios. Even on desktop computers and the latest Bluetooth chip there are a lot of problems with scatternet. Actually, you cannot do (code) much about that in many APIs anyway. Make sure your server is the master (role switch: append ;mater=true to your server URL) or your server fetches slaves manually (always master) or you do not do anything (scatternet).

  3. #3
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    Re: Is Bluetooth scatter-net possible ?

    Quote Originally Posted by traud View Post
    Does this or that help?

    The specification might be able to that, however, real implementations of today still have problems with multi-slave sceanrios. Even on desktop computers and the latest Bluetooth chip there are a lot of problems with scatternet. Actually, you cannot do (code) much about that in many APIs anyway. Make sure your server is the master (role switch: append ;mater=true to your server URL) or your server fetches slaves manually (always master) or you do not do anything (scatternet).
    Links that you have given are fantastic and I learnt several new things about Bluetooth such as the ""bluetooth.connected.devices.max" property and the limitations of the Series 40 devices versus the S60 devices.
    Well I haven't done anything practical yet on Bluetooth so I wouldn't know and most of what you say I cannot understand due to my limited knowledge of Bluetooth...

    Well I conclude that Scatternet operation is difficult to implement on J2ME enabled devices and might turn out to be buggy or the operation may not be consistent...

    What about one master and multiple slaves will that at least work realiably on S60 devices(since Series 40 devices have limitation of number of bluetooth connections).

    I was trying to use scatternet more as a way to increase the working range of Bluetooth from 10meters to the area of scattered clients but I think that may not work out now... Is there any other way to hop data across Bluetooth devices and increase the range?

  4. #4
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    Well, the real Bluetooth range of Series 40 is much larger …

    As written, doing scatternet is very easy as you do not have to consider (or add) anything. However, you will get into much trouble in real world as the current Bluetooth chips and their J2ME bridges are very limited. I am happy when I find one which supports master/slave-switch while connected.

    If you are new to J2ME, MIDlets and Bluetooth, I recommend to start with a book or tutorials rather than code examples as you will have to debug a lot on your own. There are a lot of bugs, tweaks and lessons to be learnt. Bluetooth is complicated. I do not have a good J2ME book at hand right now, however, start with the references of this one for JSR-82 (perhaps your library has its previous edition) or read at least the PDF coming with the specification. If you like to start with tutorials, continue here…

  5. #5
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    Re: Is Bluetooth scatter-net possible ?

    Quote Originally Posted by traud View Post
    Well, the real Bluetooth range of Series 40 is much larger …

    As written, doing scatternet is very easy as you do not have to consider (or add) anything. However, you will get into much trouble in real world as the current Bluetooth chips and their J2ME bridges are very limited. I am happy when I find one which supports master/slave-switch while connected.

    If you are new to J2ME, MIDlets and Bluetooth, I recommend to start with a book or tutorials rather than code examples as you will have to debug a lot on your own. There are a lot of bugs, tweaks and lessons to be learnt. Bluetooth is complicated. I do not have a good J2ME book at hand right now, however, start with the references of this one for JSR-82 (perhaps your library has its previous edition) or read at least the PDF coming with the specification. If you like to start with tutorials, continue here…
    How much larger is the range? of what I read of bluetooth the range is around 10mts and then I practically tried sending some info between a Nokia and a SE but it gave an error the moment I went behind a wall or moved one level up in my apartment..
    Bluetooth yes I'm new thanks for the links will go through them... why does Bluetooth require so much of testing is the implementation buggy or what?

  6. #6
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    Re: Is Bluetooth scatter-net possible ?

    Quote Originally Posted by traud View Post
    As written, doing scatternet is very easy as you do not have to consider (or add) anything. However, you will get into much trouble in real world as the current Bluetooth chips and their J2ME bridges are very limited. I am happy when I find one which supports master/slave-switch while connected.
    [/url]
    I thought that scatter-net was difficult so its good news that its not as difficult as it seems, but I don't understand the operation at the moment so I need to do some reading of the links that you have provided..
    Also I don't understand "master/slave switch" what does it mean?

  7. #7
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    Re: Is Bluetooth scatter-net possible ?

    Quote Originally Posted by KevinBoyd View Post
    I thought that scatter-net was difficult so its good news that its not as difficult as it seems, but I don't understand the operation at the moment so I need to do some reading of the links that you have provided.
    Scatter-net is easy as you simply cannot control it from within JSR-82. Either it works or not. Isn’t that easy?
    Quote Originally Posted by KevinBoyd View Post
    Also I don't understand "master/slave switch" what does it mean?
    You will understand it after reading. Basically, there are three secarios:
    1. Your (master and server) user collects all clients (slaves) manually.
    2. Your users just use your MIDlet.
      1. You specify ;master=true in the connection URL
        Your current device (master and client) connects to your server (slave). Then your server switches its role to master. This allows more clients (masters) to find your server. However, the server must support master/slave-switch while connected.
      2. You do not specify anything, every device offers a service and tries to connect to other services.
        Depending on the used Bluetooth chips it works or not. In mobile phone world, you will end up with the latter.
    Quote Originally Posted by KevinBoyd View Post
    How much larger is the range?
    Depends.
    Quote Originally Posted by KevinBoyd View Post
    Why does Bluetooth require so much of testing is the implementation buggy or what?
    JSR-82 is a very high-level API. Implementers can and have come up with many interpretations, beside the normal MIDP bug heaven.
    Last edited by traud; 2009-10-06 at 13:05.

  8. #8
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    Re: Is Bluetooth scatter-net possible ?

    Quote Originally Posted by traud View Post
    Your current device (master and client) connects to your server (slave). Then your server switches its role to master. This allows more clients (masters) to find your server. However, the server must support master/slave-switch while connected.
    Lets say I abandon scatter-net and opt for the one master and multiple slave topology...
    In Bluetooth the device that initiates the connection is the master right?

    So suppose I have say 3 mobile phones A, B and C. A will be made master and B and C slaves.
    From A I will search for devices and probably detect B and C and register them...
    That makes A the master and B and C the slaves right?
    now I can talk from A to B and vice versa and A to C and vice versa, but can I talk between B and C? or can B and C talk through A?

    Can I set up such a scenario for a Bluetooth chat application upto say 10 devices, 1 master and 9 slaves?

    beside the normal MIDP bug heaven.
    Well that sounds scary...

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