Connecting from the Road

You can also connect to your Mac’s regular File Sharing feature (Chapter 14) from over the Internet. This feature is a blessing to anyone who travels, whether with a laptop or to a branch office, because you’ll never be up a creek without a paddle if you discover that you left an important file at home.

UP TO SPEED: The IP Address Mess: Port Forwarding

There are so many ways to connect to your Mac from another computer. You can use SSH, file sharing, screen sharing, and so on. They’re easy to use—when you want to connect across your home or office network.

When you want to connect from across the Internet, though, things get complicated fast.

In that case, you need to know your home Mac’s IP address. (IP stands for Internet Protocol.) An IP address is always made up of four numbers separated by periods, like 192.168.1.104. Every computer on earth that’s directly connected to the Internet has its own unique IP address.

Now, if you have only one Mac, and it’s connected directly to your broadband modem, no big deal. You can find out its IP address by opening System Preferences, clicking Sharing, and turning on File Sharing.

Unfortunately, your Mac at home probably isn’t connected directly to the Internet. If you’re like most people, it’s connected to a router, or maybe an AirPort base station, so that several computers in your house can share the same Internet connection. In this setup, the router (or base station) has a unique IP address—not the Macs connected to it.

(The router doles out private IP addresses to each computer in your house or office, usually beginning with 192 or 10. If you check your Mac’s IP address in System Preferences, you’ll find out only its private address—not the public one that’s accessible from the Internet. To find out that information, you have to check your router or base station’s configuration screen; check the router’s manual for instructions.)

All right: How are you supposed to connect to one particular Mac if it’s connected to a router and doesn’t have a true, “public” IP address?

One solution is Back to My Mac, the remote-access feature described on Variations on Screen Sharing. It solves the behind-the-router problem for you, but it requires an iCloud account.

Otherwise, your only hope is to turn on a router feature called port forwarding. It makes the router pass signals intended for a specific port to one particular computer on the network. For example, you could direct all port-80 communications to the Mac doing Web serving and all port-548 traffic to the Mac doing file sharing.

The point is that, even with port forwarding, you still can’t access two different machines using the same port. (For some services, including SSH and Timbuktu, you can work around this limitation by logging into the machine specified for port forwarding, and then from that machine, log into the others on the rest of the network.)

Turning on port forwarding doesn’t require a programming degree, but it’s not simple by any means. For starters, the steps are different for every router model.

Fortunately, you can find guided tutorials on the Web. You can use Google to search for your particular router model, or check www.portforward.com, which offers free step-by-steps for hundreds of router models, including Apple’s AirPort base stations. Even so, try to arrange the assistance of someone who knows networking.

In this chapter, the term “your IP address” means your public IP address. If you have only one Mac, that’s its IP address. If you have a router or wireless network, use that device’s IP address—as passed along by port forwarding.

The easiest way to go about it is to use Back to My Mac, which is one of Apple’s iCloud services.

If you’d rather spend time than money, though, you can set up a remote file-sharing system on your own. Start by setting up the home-base Mac for file sharing, as directed in Chapter 14; then figure out your Mac’s public IP address, as described in the box on The IP Address Mess: Port Forwarding.

Finally, once you’re on the road, go online and proceed like this:

1. Choose Go→Connect to Server.

   The Connect to Server dialog box appears, as shown in Figure 21-2.

   

   Figure 21-2. The Connect to Server dialog box lets you type in the IP address for the shared Mac you want to access. (Ensuring that the shared Mac is turned on and connected to the Internet is the network administrator’s problem.)

2. Type in the public IP address of the Mac to which you want to connect, and then click Connect (or press Return).

   See the box on The IP Address Mess: Port Forwarding for a discussion of public vs. private IP addresses.

3. Enter your name and password, and then click Connect.

   From here, it’s just as though you were connecting to another computer on your office network (Chapter 14), although it’s a good bit slower. But when you’re in Hong Kong and need a document from your Mac in Minneapolis, you may not care.