title: Network Connection awareness in Unix Operating System
body: <p>I know that Windows has two services to determine if the system has access to the internet: Network Location Awareness (NLA) and -List Service. Basically it will become active when your network situation changes, checks the IP the system resolves for a certain hostname, does an HTTP request for a .txt file on this site and verifies the content in this text file (for example, msftncsi.com/ncsi.txt).</p>
  
  <p>How do unixoid operating systems (Linux, MacOS, iOS, Android) determine if they are connected to the Internet?  Similiar deamons to NLA?</p>