jQuery ajax() gets net::ERR_CONNECTION_TIMED_OUT on Chrome, not Firefox or Safari

jQuery ajax() gets net::ERR_CONNECTION_TIMED_OUT on Chrome, not Firefox or Safari

I'm using Chrome 58.0.3029.68 beta (64-bit) on OSX 10.12.4, with jQuery 3.2.1. I want to use an ajax call to an IP address/DNS name to see if the host is (still) responding.

I set up the ajax() call as below. Most of the time, a non-existent device/address returns the expected 'timeout' as the textStatus. (Note: Hosts that do respond will generally return 'error', because this looks like a CORS violation.)

  1. $.ajax({
  2.    url: "http://127.0.0.20",
  3.    crossDomain: false,
  4.    timeout: 6000,
  5.    cache: false,
  6.    data: {
  7.       name : "http://TestMyInter.net"
  8.    }
  9. })
  10. .always((jqXHROrData, textStatus, jqXHROrErrorThrown) =>    {
  11.   console.log(`In completion: textStatus is: ${textStatus}`);
  12. });

But... from time to time, Chrome (but not Firefox or Safari) will display "net::ERR_CONNECTION_TIMED_OUT" in the browser's Console window, and the textStatus will be set to 'error'. 

My questions:
  • Why does Chrome return this status, and not Firefox or Safari?
  • Is there a way to detect the ERR_CONNECTION_TIMED_OUT state in the completion routine?
  • What other information could I provide? 
Many thanks!