Yes, it is possible. I do it all the time. However, it will sometimes require heavy testing and configuration changes to make it work. I will try to get you started in the right direction. First of all, what I use for sending the "Magic Packets", is available for download fr om Here.. If this is set up correctly, it works every time. Next, most all of the information in Conrad's link above is correct, but there are a few things I would like to point out. The article says that you cannot port forward the magic packet. This is untrue, as I have many computers in different networks across the internet, that I must wake up, and at the same time, not have every computer on the network wake up. You can set up a port forward for each computer using a different port number, and not have to trick your routers into sending a packet to all computers. If your computer truly is S5 capable, then making sure it is turned on in BIOS, and for the network card in the computer. Also, most computer network cards require a wired connection for this to work. In most cases, wireless connection will not work, unless your computers have WWOL capabilities. In the case of port forwarding the ports for WOL, one of the most often things overlooked, is the ARP table in the router itself. Most routers today will clear out the ARP table of IP addresses that it senses in no longer online. Usually this happens within a few minutes of turning off computer, up to an hour or more. To get around this, you must set permanent ARP mappings of IP addresses to MAC addresses. This is usually accomplished through a telnet/ssh utility. The problem here is if the router loses power or is rebooted, you must telnet/ssh back in and reset the permanent mappings. I use a script for this and it is not overly complicated. The commands go typically like this: arp -s xxx.xxx.xxx.xxx yy:yy:yy:yy:yy:yy wh ere x is IP address, space, MAC address. You can find out the exact syntax by telnet/ssh into router and typing something like ARP /? A dynamic IP address hostname is a MUST, unless you have static WAN IP addresses. The software I linked to above, can be used for testing by installing it on remote computer, and set it to receive on the port that you're pointing to. It's usually best to get it to work on the local network first, that lets you know if your computer is configured correctly to start up with WOL. Then move on to WAN and configure for that. I hope this helps, and I'm sure I left some details out. But I will try to help you get this going.
I had already implemented much of the advice given above so below I describe the parts I was missing. I'm going to ask a couple of questions about RU related to this later. Also later, I'll put together a checklist that might be useful to others.
I applied Benny's advice to add a UDP port 9 port forwarding rule in my host's router and install the WOL Magic Packet Sender application he pointed me to on the Viewer machine. That was essentially the answer.
I shut down the host with the Windows shutdown command found in the Start menu.
Then on the Viewer machine I opened Magic Packet Sender and entered the DDNS domain name (I had registered with No-IP.com) in the Host Name, and the MAC address of my host adapter; and left the default protocol at UDP and port at 9.
When I clicked Send the host started up immediately.
The host and viewer were admittedly on the same subnet, however the magic packet was sent to an external IP address and thus I think over the Internet.
A little more experimenting and then a follow-up post.
Using Benny's Wake-on-LAN application above at "Here" (with extensive use Benny reports high reliability) for starting my RU host machines:
I've thus far over the Internet (with computers NOT on the same subnet) started one remote host from S5 and performed RU Viewer shutdown (to S5), and successfully repeated the start and shutdown cycle; and performed the same process with another computer pair starting from S4 and hibernating to S4.
Getting WOL working is mainly a matter obtaining a DDNS provider; and making correct settings in you router, BIOS, Ethernet network adapter (NIC), firewall, anti-malware software, and disabling "Fast Startup" under Windows Power & Sleep. Not all will always be required.
With the ability to start from S4 and hibernate to S4 on my production machine I have what I need. I'm still experimenting with starting from (the slightly preferable) S5 state on that machine but suspect that I might be up against a hardware limitation.