Java: Display request of an HttpURLConnection before sending

Question

I want to make some API calls to a server using HttpURLConnection. But the requests are not successful, returning:

Answer 1

tcpdump will work, but it can be hard to make it do what you want. NetCat is more user-friendly (here's the project page: http://netcat.sourceforge.net/ - most Unix platforms already include it).

nc -l 9999

This will listen on TCP port 9999, and when an HTTP client connects, it'll print out the full text of the request.