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Wake Your Mac Across the Internet – Port Forwarding Explained

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If you’re looking for a simple way to wake your Mac up across the Internets try out this website. You’ll need to know two things: the IP address your isp has assigned you and the MAC address of your Mac. What’s the MAC address of your Mac? A MAC address is a unique identifier assigned to your ethernet card by the manufacturer. You’ll find it in System Preferences. Click on Network, click on Advanced, click on Ethernet – like you see below.

wake up

Then click on on the Ethernet tab at the top right. The number listed as the Ethernet ID is your MAC address.

wake up

The MAC address and the IP address assigned by your ISP are the only two pieces of information you need to wake your Mac using this site: dslreports.com/wakeup

But there’s a catch. Your router needs to let traffic through on UDP port 9. Which brings us to…

What is Port Forwarding Anyway?

Hopefully you have a router between your cable /dsl modem and your computers. Or perhaps your modem also functions as a router. Most routers by default will block ALL incoming traffic that you haven’t requested. Only traffic you’ve requested is permitted in – requested by going to a website or checking for new mail or looking around the iTunes store, to name a few examples.

But sometimes you want traffic you didn’t request to come inside your network. Like when you want to contact your Mac from outside your home. Port forwarding is a common way to accomplish this. Different applications communicate using different ports. For example, web pages you’ve requested arrive on your computer using port 80.

Before we go further, let’s look at an analogy. Clients contacting a large company by telephone might all call the same phone number, like 800-555-FILK. There are tons of people inside the company, but we can use the same 800 number to reach any of them. A receptionist will answer the 800 number and pass our call along to an extension. We’re connected to the person we wanted to reach.

Here’s how the analogy maps out: the 800 number is like the IP address assigned by our ISP. The router is the receptionist who passes the call along to the right person. And the people at the extensions are the computers on our network. Each computer on our network has a MAC address and a private IP address, just like the people at the company have an extension.

Two people at the company don’t have the same extension, two computers don’t have the same MAC address or the same IP address. Likewise, our router can only pass a certain port request along to one computer on the network using port forwarding. What does that mean for you?

It means you can tell your router to forward port 9, the port required for wakeup, to one of the computers on your network. In your router, the port forwarding configuration might look something like this:

wake up

So, here’s what happens when you use a site like dslreports to wake up your Mac:

The website sends a special packet to your ISP-assigned IP address destined for UDP port 9. Your router sees the incoming request. Normally a request that comes from the Internet is ignored. But the router knows it’s supposed to accept traffic destined for port 9. Why port 9? Different applications on your Mac (or any computer) listen on different ports. The why is somewhat arbitrary, but here’s a list of applications and the (well-known) ports they traditionally use.

The router looks at its port forwarding table to see what private IP address on your network the traffic should be sent to. The traffic is passed along, your Mac receives it and wakes up. In addition to the MAC address, the private IP address is another way your computer is identified on your network. The private IP address and the MAC address are both analogous to the telephone extension in our telephone analogy.

Important: For your Mac to wake up, you need to go into System Preferences and select Energy Saver. Then click Options and make sure Wake for Ethernet network administrator access is checked. Your sleeping Mac needs to be wired to the network, this won’t wake a wireless computer. You can do the waking up from a wireless computer though.
Note: Currently, the http://dslreports.com/wakeup site isn’t working for Murphy. He believes it worked in the past. It’s possible Murphy’s new router is the culprit, a Netgear WGR614V6. He’s pretty sure it used to work with a Netgear MR814.

Another site to try: http://www.depicus.com/wake-on-lan

More on port forwarding – – see Murphy’s VNC post.

More on waking your Mac here, including a handy widget.

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6 comments to “Wake Your Mac Across the Internet – Port Forwarding Explained”

  1. Hi Murphy!

    I’m trying to wake my mac to over the internet. I’ve read this post and you other posts on this subject as well as a lot of other posts. I understand the theory and made all the settings but still can’t get it to work. Did you ever get it to work with your new router?

    Thanx!
    Wouter

  2. One more online tool to send remote Wake-On-LAN command over the Internet is “Online Wake-On-LAN” – http://wakeonlan.me

    It also allows to schedule wakeup event for up to one month toward, and has support of Wake-On-LAN password protect enabled network adapters.

    Also this site is available in lite version optimized for use with mobile phone or PDA – http://mobile.wakeonlan.me

  3. Thanks, for this information. It worked for me :)

  4. If you want to save your network use ProteMac Meter – monitoring all your activity.
    http://www.protemac.com/Meter/

  5. Way cool! Some extremely valid points! I appreciate you penning this post plus the rest
    of the website is extremely good.

  6. Amat begitu bagus dan juga sangat membalut sekali siaran. Di
    besok ya kabar terbarunya. Tenang kenal

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