this is a conceptual question I guess, considering I already fixed the issue, but the problem is, I'm not quite sure what the issue is.
I was trying to connect to a new VPS I setup, and made an ssh_key for root, ssh'd in, and then made a new user with a pw, then ssh'd him in. Then tried to connect using netbeans and it failed. Then I tried a cloud IDE, 'codeanywhere' a google chrome extension, and that worked fine. After some googling found this question
and the suggestion of adding
TL;DR edit your sshd_config and enable support for diffie-hellman-group-exchange-sha1 and diffie-hellman-group1-sha1 in KexAlgorithms:
worked, and netbeans now connects.
My question is: Why did the other things work and not netbeans? I barely understand connection algorithms but we were talking about them at work the other day, is it just that netbeans doesn't have them all? Or is my VPS setup incorrectly? Just seems weird to me, that ssh from command line (MacOSX) and the chrome extension had no problem but netbeans did.