Random Access   chris, kp & rob
In The Lab
Ad-Hoc Wireless Networking
by chris & rob

Rob: In the October '04 article, we showed our faithful readers how to create an infrastructure wireless network that shared an Internet connection. What if we just want to have two computers only talk to each other?

Chris: What you are describing is called an ad-hoc network and setting up an ad-hoc network is much the same as creating an infrastructure network. Start by creating a common SSID or name for your network. Once one system has been configured in an ad-hoc mode, the network should appear in the list of available wireless networks on the other system. After you have the systems communicating, then you can modify the settings to implement some basic security.

Rob: Let's configure a couple of systems to communicate in a peer-to-peer wireless setup. Just to make things interesting, one system will be Windows ME with a PCMCIA Wireless adapter (the system that we will configure first) and the other Windows XP with an integrated wireless adapter (the system that will join the network that we set up on the ME system).

Chris: The difference in the operating system versions only shows up in how you access the various network settings, not in the process that you must follow.

Rob: Before the operating system can use the wireless adapter, the brand-specific drivers will have to be installed. Even with Windows XP, you will likely have to install the brand-specific device drivers, although a wireless configuration utility is not really required with the features in Windows XP.

Chris: On the Windows ME system, I installed the latest D-Link DWL-650 drivers from the D-Link web site.

Rob: You've got to love the Internet for old driver support! Who knows where the original driver CD is? I leave driver CD in the box for any new piece of hardware I get and download the latest thing from the manufacturer's website.

Chris: When the wireless adapter is installed in the system, Windows ME detects new hardware and loads the appropriate drivers. The TCP/IP protocol is automatically bound to the new adapter in network properties, and Windows has already started scanning for wireless networks.

Rob: The quickest way to configure the wireless settings is to click on the tiny wireless icon in the system tray. Windows will display a window with tabs for Configuration and Encryption. The Wireless icon window includes a "Link Info" tab and an "About" tab, neither of which have any impact on your ad-hoc configuration. When you are configured for Infrastructure, the Link Info will display the link quality and signal strength, but these are blank when in ad-hoc mode. The About tab will identify firmware and driver version details if you need to check to see that you have the latest versions.

Chris: To configure the Windows ME system for our ad-hoc network, click on the wireless icon in the system tray. Select the Configuration tab in the window that is displayed. On the Configuration window, change the Mode from "Infrastructure" to "802.11 Ad-Hoc". For the SSID, change it from "default" to "Random Access" or whatever you want to call your own private wireless network.

Rob: Remember from our earlier wireless notes that all of the computers connecting to a specific wireless network must have the same SSID. You can have multiple networks operating within an area, but you can only connect one wireless adapter to a single wireless SSID network at a time.

Chris: For the transmit speed, PS mode, and Channel, we will leave the default settings. Next select the Encryption tab and change the Encryption (WEP) setting to "Disabled". You can turn this on later, but to set up your network initially, always start simple and work up, one step at a time. Click OK when done making your changes, as this system should now be ready to communicate.

Rob: To do the same thing under Windows XP, Open Network connections, right click on the wireless adapter and select properties. Click on the Wireless Networks tab, and under the Preferred networks section, click Add. Enter the SSID for your ad-hoc Network; set data encryption to Disabled, and add a check to the box at the bottom to specify that "This is a computer-to-computer (ad-hoc) network..." Click OK to save the entry.

Chris: Once a single system begins to broadcast on an ad-hoc network, the network name will appear in the Windows XP list of available networks as long as the list has not been restricted to showing only Access Points and Infrastructure networks. To connect to the network under Windows XP, locate your wireless network icon in the system tray; right click on the icon and select "View Available Wireless Networks" In the list of available networks, you should se one for the name of the SSID we created on the first system. Since no encryption has been configured it should show as being an "Unsecured computer-to-computer network". Click to select and then click on "Connect" to join the ad-hoc network. This process automatically configures your Windows XP system with the same SSID and no WEP encryption.

Rob: You should now have both computers on a wireless ad-hoc network. How do we get these systems to share folders or play games?

Chris: As with any network, a system must share its resources on the network to make them available to the other users. On a peer-to-peer network, any system is capable of making folders or printers accessible to other network users. To do this on a Windows 98 or ME system you must have Network File Sharing turned on. In the network properties, click on file and printer sharing, and then add a check mark next to "I want to share files..." Click okay to save the changes and allow the system to restart. Once this has been done, select a folder to share; right click on the folder and select "Sharing". Under Windows 98 and ME, you have the choice to enter a password for read only access, and a password for full access. You are not required to enter a password, but this provides security it terms of allowing only those people who know the password to access your files. If you allow full access without a password, anyone who connects to your ad-hoc network could see and access your files, and would also be able to add, change or delete files in the folder. To access the shared folder from the other computer, you can "Map a drive" or enter the IP and shared folder name an Explorer window. If you use a password to restrict access to the folder, you will have to use the option "Connect using a different user name" in the Windows XP Map Network Drive window. This allows you to enter the password before connecting to the resource.

Rob: Now that you've set up a basic, but "Unsecured" network has been created, turn on WEP encryption on each of the systems. Click on the Wireless Networking icon on the Windows ME system to open the configuration window again and select the Encryption Tab. Change the WEP Encryption from Disabled to 128 bit.

Chris: For the encryption key, you can generate the key using a text string or manually enter it as a hexadecimal number-letter sequence. Since the text string is quicker, let's do that. Note that the hex version of the key is generated as you type your string, and changes with each new character. This is handy, but it is the long hex key that you need for your XP system to keep connecting. One suggestion would be to use a USB drive or similar method for copying the hex key to a text file to carry to your XP system. This process is similar to the one used by the wizard that is part of the Service Pack 2 upgrade to save the settings to a removable flash drive or other media.

Rob: Here's another sneaky method:

  1. Type your text to generate the key on the first system
  2. Click on manual key to switch to the resulting hexadecimal code
  3. Copy this to a text file
  4. Cancel the WEP change (remember that your network is still insecure at this point)
  5. Save the text file to your shared folder where the other user can get it over the network
  6. Re-enable the WEP security on the first system

Chris: On the XP system, open Wireless Networks and refresh the list if necessary. Your entry for the ad-hoc SSID network name should now read "Security-enabled computer-to-computer network". When you select this network and click connect, Windows XP should prompt your to enter the key and then again for confirmation. This step is a lot easier if you can cut and paste the hexadecimal string from a text file. If all goes correctly, you will connect to the secure version of the network.

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