There was something very odd going on with my Raspberry Pi 3 after a fairly clean install of RetroPie- I spent way too much time looking at AP isolation, firewall settings, etc before I figured it out, so I thought I’d document it here for the next poor schlub.

 

Every time I’d try to connect, I’d get this error:

woodmanp-mbp:~ peter$ ssh pi@192.168.1.21
Connection closed by 192.168.1.21 port 22

I tried to launch raspi-config from the GUI and it exited too quickly. I quit emulation station and ran raspi-config again, and turning on SSH launched into apt-get install, and that seemed a lot better. After confirming that install, I still couldn’t get it. I ran a systemctl status sshd, and got back a bunch of complaints about keys (should have harvested these, whoops).  At any rate, if you’re seeing these kinds of errors, the quickest way to regenerate those keys:

sudo rm /etc/ssh/ssh_host_*
 sudo dpkg-reconfigure openssh-server

After this, I was able to ssh in no problem.