操作系统虚拟化noVNCnoVNC novnc/noVNC WebSocket 协议 https://novnc.com/noVNC/vnc.html?host=localhost&port=5901&path=&encrypt=0 https://novnc.com/noVNC/vnc.html?host=localhost&port=8080&path=vnc/&encrypt=0 https://novnc.com/noVNC/vnc.html?host=example.com&port=443&path=vnc/&encrypt=1 wss://example.com/vnc/ websockify