$ vncviewer x.x.x.x:1
TigerVNC Viewer 32-bit v1.3.0 (20140319)
Built on Mar 19 2014 at 17:09:08
Copyright (C) 1999-2011 TigerVNC Team and many others (see README.txt)
See http://www.tigervnc.org for information on TigerVNC.
Mon Jan 11 09:30:36 2016
CConn: connected to host x.x.x.x port 5901
Mon Jan 11 09:30:37 2016
CConnection: Server supports RFB protocol version 3.8
CConnection: Using RFB protocol version 3.8
В линуксе это парочка строчек. В винде - понятия не имею кроме как написать тулзу через API.