Search for Bluetooth Devices - how many it will display?

Discussion in 'Wireless Networking' started by sp, Oct 6, 2006.

  1. sp

    sp Guest

    Search for Devices looks for Bluetooth devices – but how many devices
    can it found – for an example if there is about 50 devices (10 meters
    from computer) will it display all 50 devices, and I can choose the
    device I want to connect?

    Maybe it depends from the device? But what it is the standard?
     
    sp, Oct 6, 2006
    #1
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  2. sp

    LittleMoo Guest

    It can probably "see" all of them, but only connect to 7 at a time.

    Look at Trust - Bluetooth information:
    http://www.trust.com/service/help/bluetooth/#4
    Under 4.3
    "A master Bluetooth device can connect to a maximum of 7 slave devices."

    -Dan
     
    LittleMoo, Oct 6, 2006
    #2
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  3. sp

    sp Guest

    LittleMoo napisa³(a):
    I know that I can connect to 7 at a time - but I need to know that I
    will see all of them - is there a maximum?
     
    sp, Oct 6, 2006
    #3
  4. sp

    LittleMoo Guest

    LittleMoo, Oct 6, 2006
    #4
  5. sp

    sp Guest

    Your answer is 255 inactive + 7 active at a time.

    Thank you! And the final question could you recommend and BlueTooth
    deviced that I can connect via USB compatybile with 255 inactive + 7
    active at a time?
     
    sp, Oct 6, 2006
    #5
  6. sp

    LittleMoo Guest

    Any device that supports Bluetooth will support the 255 + 7 connections - if
    you have a wireless card in your laptop then it might support bluetooth.
    There isn't one device in particular that I could recommend, but a lot of
    cell phones and PDA's use bluetooth.

    -Dan
     
    LittleMoo, Oct 6, 2006
    #6
  7. sp

    David Hettel Guest

    ### Wrong ####

    Bluetooth needs the device to be in a discoverable mode to be found as part
    of the security. As such if you are in a school with say 200 Bluetooth
    devices and you try to discover them, you may discover none of them, or just
    a few that happen to be in discoverable mode at the time.

    David Hettel

    Please post any reply as a follow-up message in the news group
    for everyone to see. I'm sorry, but I don't answer questions
    addressed directly to me in E-mail or news groups.

    Microsoft Most Valuable Professional Program
    http://mvp.support.microsoft.com

    DISCLAIMER: This posting is provided "AS IS" with no warranties, and
    confers no rights
     
    David Hettel, Oct 7, 2006
    #7
  8. sp

    LittleMoo Guest

    I was only going by the Bluetooth specs for this, not actual real-world
    situations. In theory though if there were say 50 devices all in
    discoverable mode and one laptop that has a Bluetooth USB adapter used as
    the master device then the spec says that the laptop should be able to
    (theoretically) "see" all of them. I don't know what the purpose of
    something like this would be though.
     
    LittleMoo, Oct 7, 2006
    #8
  9. sp

    sp Guest

    LittleMoo napisa³(a):
    I need to identify people that have GSM/bloetooth with discoverable
    mode, I don't want to connect them only identify. So are you sure that I
    see all of them?
     
    sp, Oct 7, 2006
    #9
  10. sp

    David Hettel Guest

    Most devices implement "discoverable" mode for only a few seconds at a time.
    As such if you had a room full of 200 people, and you told them to put their
    device into discoverable mode now, in theory you'd get a list of all of
    them. Having actually used Bluetooth, I'd say it's very unlikely you'd get a
    list of all of them in the above example If on the other hand you did not
    tell them to put their device into discoverable mode, you simply had a room
    full of 200 people with cell phones I would expect to see 0 found.

    Does that help any?

    --
    David Hettel

    Please post any reply as a follow-up message in the news group
    for everyone to see. I'm sorry, but I don't answer questions
    addressed directly to me in E-mail or news groups.

    Microsoft Most Valuable Professional Program
    http://mvp.support.microsoft.com

    DISCLAIMER: This posting is provided "AS IS" with no warranties, and
    confers no rights
     
    David Hettel, Oct 7, 2006
    #10
  11. sp

    sp Guest

    David Hettel napisa³(a):
    Next example I told 200 people to switch on BlueTooth and make it
    public. And after some days (people didn't change anything on their GSM)
    people are seating at room for 2 hours and on my computer I click Search
    for Devices - will I see all devices in the room?
     
    sp, Oct 7, 2006
    #11
  12. sp

    David Hettel Guest

    "Make it public" is not a blue tooth command, if you told two hundred people
    to switch there phone on and make it discoverable, and they attempted to do
    it, I feel safe in saying no, you'll not find them all, nor even a great
    number of then. It's very unlikely that you could get two hundred people to
    do basically the same thing within 10 seconds of each other, in my
    experience. Also as one who gives help with Bluetooth devices, it's unlikely
    that all two hundred people would even know how to make their device
    discoverable. This is something you might normally do once or twice a year
    with a manual telling you how. It's generally not straight forward to
    accomplish or simple. Normally it's buried several menus down in the device.
    Different firmware on a device may also change where and how you do this, so
    even if everyone had the same model of phone, different firmware can change
    how you do this. Another potential problem is there is not one way of
    displaying the Bluetooth devices discovered. Some devices may keep past
    devices, and others if they are not refound will drop them from the display.
    So say you "hunt" for devices and find 75, devices in the first 10 seconds,
    in the next scan you find 50, some of the 50 may be the same as those found
    in your first scan, but some of the first scan may no longer be in
    discoverable mode, so they are removed from the list of those displayed. Do
    you see the problem here, you may need to get all in the same mode, within 2
    to 3 seconds of each other, to give your device time to talk to each one it
    sees.

    So yes in theory it may work, in reality I'd need to see in demonstrated
    with a random group of users before I'd believe it. And I would never count
    on it working.

    --
    David Hettel

    Please post any reply as a follow-up message in the news group
    for everyone to see. I'm sorry, but I don't answer questions
    addressed directly to me in E-mail or news groups.

    Microsoft Most Valuable Professional Program
    http://mvp.support.microsoft.com

    DISCLAIMER: This posting is provided "AS IS" with no warranties, and
    confers no rights
     
    David Hettel, Oct 7, 2006
    #12
  13. sp

    sp Guest

    So yes in theory it may work, in reality I'd need to see in demonstrated

    The first establishment is that one day I will configure all phones and
    the second establishment is that people don't change anything (settings)
    on their mobile phones.

    And after some days they meet toogether in one room and I would like to
    press Search for all devices in range (I can click it several times) and
    for example for about 30 minutes I will find them all. Is it true or
    not? (Of course - I will write application for it).


    Does .Net 2.0 support bluetooth communication especially Search for all
    devices?
     
    sp, Oct 8, 2006
    #13
  14. sp

    LittleMoo Guest

    For .Net development under Windows XP, 2000, etc. the short answer is no.
    For .Net development under Windows CE (for Pocket PCs) you would be able to.

    However - there is at least one way to use .Net under XP for Bluetooth
    development, but it is not free. It's an SDK called BlueTools (about $100):
    http://franson.com/bluetools/

    You might be able to accomplish this by using WidComm drivers and the
    Microsoft Bluetooth Stack drivers in a .Net application - but as there is
    probably poor documentation of these drivers under XP at best then this
    would be very hard to accomplish.

    -Dan
     
    LittleMoo, Oct 9, 2006
    #14
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