RE: RE : RE : [lwip-users] Finding assigned IP address of device

[Bill Florac]

Look at implementing SLP protocol...it should do the trick. Or, roll your own 
but use multicast rather than broadcast. While router can limit multicast, most 
don't. 

Bill

-----Original Message-----
From: address@hidden [mailto:address@hidden On Behalf Of Jonathan Larmour
Sent: Thursday, February 21, 2008 12:45 PM
To: Mailing list for lwIP users
Subject: Re: RE : RE : [lwip-users] Finding assigned IP address of device

Bill Auerbach wrote:
>> Piero 74 wrote:
>>> but AFTER ip discovery, sw on pc have to use this ip for tcp connection.
>>>
>>> i think if you use cable cross between two systems which have in general
>>> IP in different subnet, you cannot comunicate. I think it could works
>>> only if they have the same GW... but it will be a strange situation.
>>>
>>> I said "but, using broadcast, the installer have to configure his laptop
>>> on the same subnet of board". It means configuration necessary AFTER ip
>>> discovery
>> But you're also going to have to configure the laptop to communicate with
>> the subnet the static IP address is on too. And you're stuffed if
>> 192.168.* (or whatever you're using) is already a valid subnet connected
>> to the laptop.
>>
>> A broadcast to 255.255.255.255 will be seen by every host on the same side
>> of a gateway router, directly connected with a cross-over cable or not.
>> The configured gateway for each subnet is not relevant.
> 
> I see this is more complicated than I realized - and hoped.  One thing,
> somewhere it was mentioned some routers will block broadcasts.  If that's
> the case, then do I need to implement more than one scheme and try both
> until I get a response?

Routers block broadcasts in the sense that they do not pass broadcast
packets onto different physical segments with different subnets. In all
likelihood you are on the same physical network, in which case the
broadcast will be received.

Passing multicast through the router usually requires special router
configuration.

Jifl
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