Q I have a Mac with AirPort (wireless) card and I have a friend that comes over with a wireless PC. How can I share my Internet connection with the PC?

A. If you have a Mac or a PC with a wireless card you can share your Internet connection by turning your computer into a Wireless access point. All wireless (WiFi) devices connect to an access point and in most cases the access point is built into a router. Using two or more computers you can create a computer-to-computer network, also called an “ad hoc” network.

To begin with you need to configure your Mac to share your Ethernet connection using the Airport. Start by opening “System Preferences” from the Apple Menu, and then click the “Network” icon. You should see the available network interfaces, Ethernet, Airport Internal Modem – the green dot indicates that the connection is working. (If you don’t see the “Network Status” you can choose it from the “Show:” pull down.) Your Mac should be connected to the Internet using the Ethernet interface. (It is also possible to share a modem connection – while the modem is connected.) Double click the “Airport” section or click “Configure…” The first tab from the left should say “Airport” and at the bottom we’re going to check the box saying, “Show Airport status in the menu bar.”

In the menu bar you should now see an inverted cone icon with a curved top. That is the Airport icon. (Sometimes it’s empty or it may have bars if you are connected to a wireless network.) Click on the icon to open the menu and choose “Create Network”. The “Computer-to-Computer” dialog box will open and you can enter a unique name or “SSID” for your network. For security you should also check “Enable encryption (using WEP)” and enter a password. The 40-bit password is made up of 10 characters (using 0-9 and A-F only.) An easy to remember password would be a phone number with the area code. (Note: If you’re really concerned about security you should make up a more secure password. If your planning on doing wireless networking a lot you may want to consider buying a wireless router.)

Now that you have created a wireless access point you can share your Internet connection. This time go to “Sharing” in the “System Preferences” application. Click on the “Internet” tab and you’ll see “Share your connection from” with “Ethernet” section selected. Check the box next to “Computers using Airport”. (By the way if you’re connected to the Internet via Airport you can share the Internet via your Ethernet connection.)

Now we’ll switch our attention to your friend’s PC. (We’re only going to discuss the standard Windows XP method. Many wireless PC’s use proprietary software – but the steps are very similar.) On the PC may see a wireless Network icon in the lower right end of the Task Bar. You can also click on “Start” (lower right) and pick “My Network Places” from the menu. On the left of this window click “View Network Connections”.

If you clicked on the wireless icon from the lower right, you can choose “View Wireless Networks” from the “Connection Status” and then choose “Change Advanced Settings”. (You can click “Connect” if you see the SSID in the list. You may get asked for the network key, if not read on.) From the “Wireless Networks” tab select the “SSID” you created on the Mac and choose “Properties”. Under Network Authentication choose “Shared” and “WEP” then enter the Network Key. The Network Key is the password we created above (You may have to uncheck “The key is provided for me automatically.” Click “OK” to save and close the two windows.

At this point you should see the SSID listed as automatic. You will also see a small PC icon has a green wireless icon in the task bar (lower right). At this point your friend’s PC should be connected to the Internet via your Macintosh. Your friend’s PC will remember your network when he brings the computer back for a visit.

If you want to share the Airport connection with another Mac, choose the SSID from the Airport menu on the second Mac. A dialog should ask you for the Password. Enter the network key and choose the same encryption method. You should be connected – you’ll see that the Airport resembles an amphitheater when it’s connected. When you’re finished sharing uncheck “Create Network” from the menu on the host Mac.