There have been reported issues involving the inability to connect to NX involving the specific error message of "ssh_exchange_identification: Connection closed by remote host" such as:

NX> 203 NXSSH running with pid: 1453153

NX> 285 Enabling check on switch command

NX> 285 Enabling skip of SSH config files

NX> 200 Connected to address: 83.135.150.113 on port: 22

NX> ssh_exchange_identification: Connection closed by remote host

This error may also present itself when attempting to add a new NX user via "nxserver --useradd xxxx" where xxxx is the username.

This problem is caused by an already documented configuration issue with ssh that can be referenced here:

http://www.snailbook.com/faq/libwrap-oops.auto.html

By following the guidelines on that site, the user should be able to prevent this error from presenting itself.