 now, we've always used links (GET) and HTML forms (POST) to get data from the ESP, or to send data to it. This always resulted in a browser navigation action. There are many situations where you want to send data to the ESP without refreshing the page. 
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        One way to do this is by using AJAX and <a href="https://developer.mozilla.org/en/docs/Web/API/XMLHttpRequest">XMLHTTP requests</a>. The disadvantage is that you have to establish a new TCP connecti