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We are using the iPad to make an ad-hoc wireless connection to our proprietary device. DHCP is not available, so we are using addresses in the Auto-IP range. The user selects the device from the list of wireless networks on the iPad and about twenty seconds later, DHCP fails and an Auto-IP address is assigned. The device has a fixed IP address of 169.254.20.10.

The problem we are having is that from time to time, the iPad loses it's ability to connect with the device. This issue appears to happen much quicker with the iPad 4th generation and iPad Mini. Usually a combination of switching to another wireless network on the iPad and then back to the ad-hoc network and/or turning Wi-Fi off then back on again fixes the issue, but sometimes the iPad needs to be restarted.

When it gets in this state, the socket errors we receive in our app when we try to unicast to 169.254.20.10 or broadcast to 169.254.255.255 are either 'Host is down' or 'No route to host'. This is confirmed by using an app such as IT Tools to ping the device.

Any ideas what might be going on or how we fix this issue?

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Can you instead set the IP address of the iPad manually, so you aren't relying on DHCP? –  Ashley Aug 9 '13 at 13:04
    
That's been a hard sell in that it really complicates the setup time/effort for our end users. I should mention as well that in a perfect world, we would have a DHCP server in our proprietary device. Unfortunately, we have to do without at this point. –  bvanderw Aug 9 '13 at 14:26
    
OK, my next step would be to record the information shown in the IT Tools app for Interface, Route and ARP (all in the More tab) during the working and error states, then compare the two. Working through the layers involved (I think: I'm a bit rusty here really), perhaps the iPad has lost its IP address, or the route to the device, or the ARP entry for the device. Then again, if we could figure that out, we have a narrower definition of the problem, but there's still no guarantee of being able to solve it. –  Ashley Aug 9 '13 at 23:20
    
Another work-around idea: can you introduce an additional WiFi router (including a DHCP server) into the situation, and have your device join the network that it creates? –  Ashley Aug 9 '13 at 23:21
    
One more idea: if you set up an ad-hoc network on a Mac and connect to that with the iPad, does the iPad drop the connection in the same way? (I'm trying to isolate the problem to the iPad or the ad-hoc network.) –  Ashley Aug 10 '13 at 0:15

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