Can't see localhost from UWP app
<p>I’m working on UWP app on my laptop.  On a previous laptop with a pre-release Windows 10, I was able to get my app to see my web API service on localhost, but on this laptop, no matter what I try, I always get this error using HTTP client:</p>

<blockquote>
  <p>A connection with the server could not be established</p>
</blockquote>

<pre><code>var response = await client.GetAsync(BuildGetRequest()).AsTask(source.Token);
</code></pre>

<p>If I point to my published service on Azure, everything works fine.
Here’s what I have tried:</p>

<ul>
<li>Allowed local network loopback is set in the App’s project properties.
Confirmed that my app package name is checked in the AppContainer Loopback Exemption Utility in Fiddler.</li>
<li>Set Internet (Client), Internet (Client &amp; Server), Private Networks capabilities in Package.AppManifest</li>
<li>Tried manually setting c:>checknetisolation loopbackexempt -a -n= from the command line</li>
<li><a href="https://stackoverflow.com/questions/33259763/uwp-enable-local-network-loopback">UWP Enable local network loopback</a></li>
<li>Completely disabled the firewall in an act of pure desperation.</li>
<li>Run my Web API in full IIS rather than IIS Express.</li>
</ul>

<p>Nothing makes any difference.</p>

<p>I have noticed that I’m having a similar problem in Edge, despite allowing Localhost loopback in <code>about:flags</code> and several other suggestions I found at:</p>

<ul>
<li><a href="https://social.technet.microsoft.com/Forums/en-US/0face535-3c7a-4658-be34-6c376322ca34/microsoft-edge-cant-open-local-domains" rel="noreferrer">https://social.technet.microsoft.com/Forums/en-US/0face535-3c7a-4658-be34-6c376322ca34/microsoft-edge-cant-open-local-domains</a></li>
</ul>

<p>My Web API project runs fine in every browser except Edge, so I’m guessing as Edge is a universal app, the problem is linked. When I debug it in Edge, I get this error:</p>

<blockquote>
  <p>Can’t connect to the proxy server</p>
</blockquote>

<p>If I go to <code>Settings</code> and switch off the manual proxy server, run it again I get:</p>

<blockquote>
  <p>Hmm, we can’t reach this page</p>
</blockquote>

<p>I notice though that for some reason the Manual Proxy server setting keeps switching back on during subsequent runs.</p>

<p>Could anyone suggest anything else I could try to get my UWP app to see my service on localhost?</p>