How to check the sent POST request through the Online service?

Question

Arduino

Arduino uses the EtherCard.h library to send POST requests. To debug the correctness of the POST request, I am looking for an online service to which you can send a POST request with its subsequent display and, possibly, analysis for errors.
There are a number of solutions that help generate a POST request ( here are examples ), but unfortunately I did not find a service for checking the receipt of a request.
Perhaps there are solutions inside the browser.

Answer 1

services - requestb.in and https://www.runscope.com
and so - any network sniffer on your computer.

Answer 2

3 lines in Go with the output of everything coming to the console or to the log.