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Re: [ecf-dev] Connection awareness API

Thanks for the info Scott. As I said earlier I was just curious to know if
we had anything already available and I can definitely do without it.

PaScaL


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  |Scott Lewis <slewis@xxxxxxxxxxxxx>                                                                                                                |
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  |"Eclipse Communication Framework (ECF) developer mailing list." <ecf-dev@xxxxxxxxxxx>                                                             |
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  |01/18/2008 12:06 PM                                                                                                                               |
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  |Re: [ecf-dev] Connection awareness API                                                                                                            |
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Pascal Rapicault wrote:
      What we are after in p2 is probably something like 1). Basically we
      would
      like to handle gracefully the fact that the machine is not connected
      to the
      network so that we could avoid prompting for silly things like "the
      file
      does not exist", or not prompt the user to retry the download.


OK.  AFAIK, there is no cross-OS (java) API for getting that low-level
info.  I think native code would have to be written.  Please others speak
up if you know of something that provides cross-platform info on the lower
layers (physical, link, network).  I don't think that in the case of
windows it even exists at the winsock level (although I'm not sure about
that).

We could easily create a piece of code that checked for reachability to a
particular server/servers (e.g. www.www.eclipse.org)...and assume that if
that connectivity is present that the network is functioning (and if it's
not present that the network is not functioning), but this has some very
obvious limitations.

Scott




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        |01/17/2008 04:55 PM
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        |Re: [ecf-dev] Connection awareness API
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      Hi Pascal,

      This is a tough question to answer yes/no...because the answer
      depends
      upon exactly what you mean by 'network is up'.

      First, from a given process, 'the network' can/could mean a variety
      of
      things:

      1) The OS device (/eth0) is installed/working/connected at media
      layer
      (e.g. wifi)
      2) TCP/IP stack installed/active (obviously includes localhost)
      3) DNS is functioning
      4) A specific remote machine (e.g. gateway) is reachable (e.g. ping)
      5) TCP/IP and/or UDP can be used for accessing a particular server
      and/or peer
      6) Accessing a set servers/peers (how much of 'the network').

      Also, there is a further subtlety...between a) determining whether
      each
      of these levels is working (without a specific connection being
      formed),
      and b) being notified if an existing connection goes down.

      Most ECF providers have plenty of support for b...and this is
      provided
      via async notification of IContainer disconnection (once in connected
      state of course...which, depending upon underlying protocols
      used...e.g.
      IP/UDP/DNS/TCP, support such notification).  If detection of network
      failure is what you are interested in, then the answer is generally
      'yes'...for most/many providers.

      In general, we don't provide cross-transport (or cross-OS) APIs for
      accessing the state of the physical, data link, and network layers
      (in
      OSI terms 1, 2, and 3 above)...mostly because these are specific to
      hw-specifiic, OS-specific and tcp/ip stack-specific APIs.  So if
      that's
      what you are asking the answer is generally 'no' (excepting the
      discovery API with some providers).

      Also...if you would/could describe the use case a little further,
      I'll
      happily respond with more brevity :).

      Scott


      Pascal Rapicault wrote:

            Hello,

            Does ECF provide an API to know whether or not a network is up
            on the
            machine?

            Ths

            PaScaL

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