Learning from the udacity course on client server communication course link: https://classroom.udacity.com/courses/ud897 Using netcat: nc google.com 80 <head/get/post/put> headers: OPTIONS: get a list of methods supported by the URL end point HEAD: just the header and not the body.. validate if the incoming data will fit the memory, cache validation xml-http-request: xhr, traditional way of doing ajax, new way is javascript promises which are chainable callbacks and are asynchronous How head is used for cache checking.