Networking

Get IT Done: Configure Windows 2000 Professional Direct Cable Connections

Learn how to configure Direction Cable Connections properly, so your computer can access resources anywhere on the network.


Taking a laptop computer on the road can be a challenge. Not only do you have to lug the thing around the airport and run it through the X-ray machine, you also have to try to get enough tray space on the airplane to actually get some work done. And inevitably, you have to connect the machine to the network when you get to your destination.

Connecting to a network using Windows 2000 on a laptop is as simple as plugging the dongle into the PC Card NIC and plugging the cable into a hub. However, accidents do happen, and the time may come when the PC Card slot has sticky cola residue in it that prevents it from working. Now what do you do? You can search desperately for a dongle that works with your card, or you can take advantage of Windows 2000 Professional’s Direct Cable Connections. Using Direction Cable Connections, you can use a serial cable, parallel cable, or infrared device to connect two computers. Also, if you configure the connections properly, you can allow your computer to access resources anywhere on the network.

In this Daily Drill Down, we’ll take a look at how to configure a direct cable connection using a special serial cable called a null modem cable. These cables are easy to find, and most desktop machines have one or two serial ports available. To get your laptop connected to another laptop or a desktop computer, you’ll have to address the following issues:
  • Preparing the machines for the direct cable connection
  • Configuring the connections on the Host and Guest computers

After you prepare the machines and configure the connections, the machines will be ready to establish a direct connection with one another.

Preparing the computer for the direct cable connection
Before you set up your direct connection between the laptop and the desktop computer, you have to take care of a couple of preparatory steps. You must:
  • Obtain a null modem cable.
  • Check for available serial ports.

After you get the proper cable and confirm that you have available serial ports, you can configure the connections.

Obtain a null modem cable
A null modem cable is a RS-232C serial cable that reverses the normal pin contacts. This serial crossover cable allows the serial cable to be used to connect two computers, rather than connecting a computer to a modem. Null modem cables are often used to:
  • Allow two players to play a game with one player at each machine.
  • Test a computer by checking its responses from another computer.
  • Create a network connection when a NIC or hub/switch is not available.

Tip
When you purchase a null modem cable you should be able to find it with the serial cables. However, make sure that the cable is marked as a null modem cable. Do not use a conventional serial cable, as it will not work.

Another thing to watch out for when buying the null modem cable is to ensure that you have the correct DIN connectors. Remember that serial ports can have 9 or 25 pins. You might want to have on hand two null modem cables with the following specs:
  • DB9 (Female) to DB25 (Female)
  • DB9 (Female/Female)

You’ll be safe if you have both of these, since some computers have either the DB9 or the DB25 but not both.

Check for available serial ports
In order to create a successful null modem connection between the serial ports, be sure there is an available serial port on each computer. Both the laptop and the desktop must have at least one available serial port. If there is a device, such as a modem or scanner, attached to one of the serial ports, you can detach the device and attach the null modem cable.

If there are no devices already connected to each machine’s serial port, you need to confirm that Windows 2000 has identified the ports and that they are functional. You can check the functionality of the serial ports by performing the following steps:
  1. Right-click the My Computer object on the desktop and click the Properties command.
  2. On the System Properties dialog box, click the Hardware tab and then click the Device Manager button.
  3. In the Device Manager window (Figure A), expand the Ports (COM & LPT) node. If there is a COM1 and/or a COM2 without a red “x” on it, then you have working serial ports you can use for the direct connection.

Figure A
Checking the serial port status in Device Manager


If you don’t see a COM port available, you should check the system BIOS. Sometimes the COM ports are disabled in the BIOS and you have to manually enable them. Once the port is made available in the BIOS, the Windows 2000 Plug and Play mechanism should find and configure the serial port without your intervention.

Configuring the connections
After you have confirmed the availability of the serial ports, plug the null modem cable into the serial port of each computer. Make a note of which serial port you are using in each computer. Most laptops have a single serial port, so you should not have trouble identifying the port on the laptop. However, most desktop machines have two serial ports. New machines have these ports marked. If the ports are not marked, try one port and, if you receive an error message during the connection attempt, change the cable over to the other port. Once the cable is connected, you can begin to configure the connections.

Setting up the Guest computer
Having one machine “call” the other makes the connection. The Guest computer is the machine that will make the call. Typically, the laptop will initiate the call to the desktop. To set up the Guest computer, perform the following steps:
  1. From the Settings menu in the Start menu, open the Network And Dial-up Connections window.
  2. In the Network And Dial-up Connections window (Figure B), double-click the Make New Connection icon.
  3. The Welcome page will appear. Click Next.
  4. On the Network Connection Type page (Figure C), select Connect Directly To Another Computer and click Next.
  5. On the Host Or Guest page, select the Guest option and click Next.
  6. On the Select A Device page (Figure D), click the down arrow on the drop-down list box, select the COM port you wish to use, and then click Next.
  7. On the Connection Availability page, select the Only For Myself option for best security. Choose For All Users if you have modest security requirements, and then click Next.
  8. On the Completing The Network Connection Wizard page, you have the option to change the name of the connection. Accept the default or change the name, and then click Finish.

Figure B
Double-click the Make New Connection Icon in the Network And Dial-up Connections window.


Figure C
Select the Connect Directly To Another Computer option.


Figure D
Select the COM port on the Select A Device page.


Setting up the Host computer
The Host computer is the machine that accepts the call from the Guest computer; it’s typically the desktop machine. To configure the Host computer, perform the following steps:
  1. From the Settings menu in the Start menu, open the Network And Dial-up Connections window.
  2. In the Network And Dial-up Connections window, double-click the Make New Connection icon.
  3. The Welcome page will appear. Click Next.
  4. On the Network Connection Type page (Figure C), select Connect Directly To Another Computer and click Next.
  5. On the Host Or Guest page, select the Host option and click Next.
  6. On the Connection Device page, select the COM port you wish to use and then click the Properties button. You will see an information dialog box informing you that the COM port is not yet ready for the direct connection but that it will be enabled after the wizard is completed. Click OK to close the dialog box and then click Next.
  7. On the Allowed Users page (Figure E), select the users that you wish to allow access to the Host machine. Note that the Guest account has no password. Click Next.
  8. On the Completing The Network Connection Wizard page, you will see that the name of the connection is Incoming Connections. You cannot change this name. Click Finish to complete the wizard.
  9. In the Network And Dial-up Connections window, double-click on the Incoming Connections icon and click on the Networking tab. Click on the Properties button and you will see the Incoming TCP/IP Properties box (shown in Figure F).

You can allow callers to access the rest of the network if you check the Allow Callers To Access My Local Area Network check box. If there is a DHCP server on the network, you can select Assign TCP/IP Addresses Automatically Using DHCP. If there is no DHCP server available, you can select Specify TCP/IP Addresses and then put in a start address and end address for the block of IP addresses you wish to assign to clients. Click OK after making your selections and then click OK again.

Figure E
Select users for access to Host machine.


Figure F
Configuring TCP/IP properties of the Host machine.


Making the connection
To establish the connection between the Guest and the Host machines, double-click the icon in the Network And Dial-up Connections windows for the Direct Connection on the Guest machine. You will see the logon dialog box that appears in Figure G. Note that the Guest account has no password. Click Connect.

Figure G
Making the connection from the Guest computer without a password


After the connection is complete, you will see on the Host machine the name of the icon for the Incoming Connections change its name to Unauthenticated User, as seen in Figure H.

Figure H
Notice how the Incoming Connections icon changes to Unauthenticated User after connection is established.


If the client connection was configured to use TCP/IP, then the client will be able to access not only the content on the Host machine, but will also be able to connect to resources anywhere on the network. Note that you do not need to use TCP/IP; any common network protocol will work. The only practical difference between this connection and an Ethernet connection is that the serial cable direct connection is much slower.

Conclusion
In this Daily Drill Down, you learned about how you can use direct connections to directly connect two computers without the need for network cards. We looked at the specifics of using serial ports to create the direct connection. Similarly, connections can also be made using either parallel or infrared ports. By using a direct serial connection, you can access resources on the computer you directly connect to, as well as other computers on the network. All that is required is an available serial port on the host PC and a null modem cable. The primary difference between an Ethernet connection and a cable connection is speed.

Editor's Picks