Re: LAN and GPRS

From: oaix (wenxb_at_hotmail.com)
Date: 04/30/04 

Date: Fri, 30 Apr 2004 08:31:03 +0800

Done. :) Thanks a Lot.
"Scott Herriman" <sch@callwave.com> wrote in message
news:Osa9ybZLEHA.2100@TK2MSFTNGP10.phx.gbl...
> I second the notion of using IP Helpers. It is difficult to know what the
> order of precedence of your connections is. In my recent findings it
> appears to work like a push down stack. Starting a VPN after a RAS
> connection after a LAN (comes up at boot) is different then RAS after a
VPN
> after a LAN. To solve this problem IP Helpers will do one thing. You can
> get an event when the routing table changes, look at NotifyRouteChange &
> NotifyAddrChange. This will let you know when these tables change. You
> should be able to compare a previous snapshot with a new snapshot to
decide
> what action to take.
>
> Yes you can bind to a specific port for TCP. Enumerate all the interfaces
> on the machine (gethostbyname or GetIfTable) and bind to each of the
> interfaces (or the one that you prefer). When you send data you just need
> to indicate which interface is the preferred interface.
>
> I would abstract away all these details from the service itself. You
could
> have a low level socket interface that does the following:
> * Determines which interfaces are available. GetIfTable
> * Notices when the list of interfaces changes and updates
NotifyRouteChange
> NotifyAddrChange
> * Binds to the proper interface(s)
> * Sends on the preferred interface.
>
> Of course using TCP the stream will be broken when an interface goes down
> and you will not want to change sending sockets until the connection is no
> longer needed. Sounds to me like you need a socket pool. You check out a
> socket and use it until done.
>
> Scott
>
> "Eugene Gershnik" <gershnik@hotmail.com> wrote in message
> news:%23VU9OFOLEHA.620@TK2MSFTNGP10.phx.gbl...
> > oaix wrote:
> > > Thanks.
> > >
> > > all i need to do is set up a TCP/IP connection with my app server.
> > > if LAN is avaiable, i will use LAN, when LAN is unavauable, i'll
> > > connect via GPRS.
> > >
> > > the problem is , once the GPRS is connected, it override the LAN
> > > setting . so when i plug in the LAN cable, i have to play with the
> > > routing table and make it works but all is by manually, how it could
> > > be done by script?
> >
> > For a programmatic way check IP Helper documentation in MSDN. If you
want
> to
> > expose this functionality to scripts you will have to wrap IP Helper
> > functions in a script-friendly COM wrapper.
> >
> > > my question is the routing table is the only way to slove it?
> >
> > The correct way is to go through routing table. It captures user desires
> > regarding how a connection to a specific destination should be made.
> >
> > > we
> > > can't make it at socket level, right? as i know you can 't bind to a
> > > select IP for a TCP/IP client.
> >
> > Well for UDP there is SO_DONTROUTE but MSDN says that Windows doesn't
> honor
> > it.
> >
> > --
> > Eugene
> >
> >
> >
>
>

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