title: Why would AzureSearch SDK spontaneously fail with transport connection issue?
body: <p>We had some big excitement yesterday.  Two of our web apps (both deployed and untouched for at least 3 months) that use AzureSearch's SDK stopped working at different times (one early morning; the other in the evening).  The indexClient.Documents.Search method started failing with this error:  </p>
  
  <p><em>HTTPS handshake to XXXXsearch.search.windows.net (for #435) failed. System.IO.IOException Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host. &lt; An existing connection was forcibly closed by the remote host</em></p>
  
  <p>After a mad google scramble we added these 3 lines just before the search which fixed it.</p>
  
  <pre><code>            const SslProtocols _Tls12 = (SslProtocols)0x00000C00;
              const SecurityProtocolType Tls12 = (SecurityProtocolType)_Tls12;
              ServicePointManager.SecurityProtocol = Tls12;
  </code></pre>
  
  <p>All I can imagine is we missed some kind of "AzureSDK is changing" email?  This was very bad and we got lucky on a quick solution or it could have been a disaster.  Does anyone know why this would have happened?</p>