where host is the host where the listening viewer is running. If it's not listening on the default port of 5500, you can specify host:port instead. vncconnect is just a simple X program which sets a property on the root window - it is Xvnc which actually makes the connection. Any feedback about the success or failure of the connection will appear in the log file for Xvnc rather than on the terminal where you run vncconnect.
Note also that the DISPLAY environment variable or the -display option must be set as appropriate to control Xvnc. If you run it on an ordinary X server then nothing will happen.
VNC was originally developed by the RealVNC team while at Olivetti Research Ltd / AT&T Laboratories Cambridge. It is now being maintained by RealVNC Ltd. See http://www.realvnc.com for details.