Vnc
From DWIKI
FAQ
main: reading version failed: not an RFB server?
It has no idea what's going and has no proper error handling. Try telnetting to the port and wait a few seconds to get better information.
Server did not offer supported security type
You're probably trying to connect to realvnc, use realvnc viewer
tigervnc: No matching security types
You're probably trying to connect to realvnc, use realvnc viewer