Java userspace test (contrib/external-tests/java)

[crasm at wireguard.1.email.vczf.io]

Hello,

I've written an initial attempt for a java userspace test in
[contrib/external-tests/java][], but am currently not getting any
response back from my own wireguard server or the demo server. 

[contrib/external-tests/java]:
https://github.com/crasm/WireGuard/blob/master/contrib/external-tests/java/src/main/java/wireguard/Main.java

I'm fairly sure the problem is in my code, but I'm not sure how to
debug. Is there anyone who would be willing to take a look at this and
compare it to the other external tests?