I have done first
yum -y install tigervnc-server Then
vncpasswd in order to set a password to vnc. Then I have started the vncserver on my guest with
vncserver :1 -geometry 800x600 -depth 24, even you can see in the picture that the server is up:
And when I go to Windows 10 to connect with UltraVNC Viewer and I type the Host-Only IP the program says to me
failed to connect to server even connecting with port (5901) or with display (1).