title: Ping results in "Host is Down" (but it's not!) error after iOS 10 Update
body: <p>I have an iOS application that is a simple client or "remote" that sends some bytes to a hardware device when the user presses buttons within the application. The hardware device is an Arduino with a <a href="https://www.sparkfun.com/products/retired/11049" rel="nofollow">WiFly shield RN171</a>. The device broadcasts an AdHoc WiFi network. Upon connecting to the AdHoc network, the iPhone will have an IP Address in the 169.254.0.0/16 subnet. The hardware device has an IP address of 169.254.1.1.</p>
  
  <p>Since updating to iOS 10, the application cannot connect to the hardware device and receives the error "Host is Down". As a means of troubleshooting, I installed a generic Network Ping tool from the App Store, which yields the same error: "Host is Down" when I attempt to ping the hardware device 169.254.1.1 from the iPhone.</p>
  
  <p>I can however, ping the iPhone from the hardware device.</p>
  
  <p>This is a non-issue in my "development phone" which is still running iOS 9. The app happily connects to the hardware device, and the same "Network Ping" tool can ping the hardware device no problem.</p>
  
  <p>I'm wondering if there are any changes in iOS 10 to the Networking tool set that might have introduced this problem? I cannot find any resources that would say so, nor am I sure how I can troubleshoot this issue...</p>