While the article seems to be focused on lower-level stuff, I feel like Charles (http://www.charlesproxy.com/ http://www.charlesproxy.com/) is worth mentioning

While the article seems to be focused on lower-level stuff, I feel like Charles (http://www.charlesproxy.com/ http://www.charlesproxy.com/) is worth mentioning when the discussion of diagnosing/debugging the network comes up. A startling number of network requests are now going over HTTP (all those apps using HTTP endpoints, the huge influx of web apps in the last few years, etc.). Charles is probably the easiest way to debug (and simulate other network environments) that I've used.