PXE is pretty much confined to x86 type boxes. If you are running Solaris x86 is may be possible to use PXE to provide a boot image.

Is you have a Sun Sparc based system, you can do a "Stop A" to get to the "OK" prompt. From there you can run "boot net" or "boot net -install" depending on your intentions. This will look for a Jumpstart Server (another Sun box). It will use bootp to locate this machine and optain an IP address. Sun has some Jumpstart docs you can read for more information.

In order to do either of the above remotely you will need some sore of remote console. For older boxes, you may want to go with a Digi Portserver type solution. For new boxes, they typically have a LOM (lights out management) network port you can configure. This gives you console access over the network and is available as long as the power cord has power running through it even if the system is powered off.