Help with itunes sharing

Hi everyone im new here and just needed some help with my itunes setup.I have 3 macs:G4,G5 and Macbookpro.
I am able to share Itunes with the wireless Macbook and the ethernet G4.I am ,however, unable to see any of those or have them see my ethernet G5.I am fairly competent with computers and have checked and rechecked my settings but cannot see why it is not working.Any help would be greatful as its starting to hurt my head now banging it on the keyboard.

 

can anyone help me with this...?

Thanks in advance.