iOS 9 introduced App Transport Security, which by default forces apps to communicate over HTTPS instead of HTTP. This is a great default for production apps, but it can get in the way of connecting to development servers which are less likely to be configured with a HTTPS connection, especially when running on your local machine.

To get around this an exception can be added for localhost (or any other known development environment domain) which will allow your app to send and receive unencrypted HTTP requests. In your Info.plist add the following:

<key>NSAppTransportSecurity</key>
<dict>
  <key>NSExceptionDomains</key>
  <dict>
    <key>localhost</key>
    <dict>
      <key>NSTemporaryExceptionAllowsInsecureHTTPLoads</key>
      <true/>
      <key>NSIncludesSubdomains</key>
      <true/>
      <key>NSExceptionAllowsInsecureHTTPLoads</key>
      <true/>
    </dict>
  </dict>
</dict>

If you’re editing your Info.plist visually in Xcode, you should have these entries: