Figure 1 Dialog to authorize a share
Revised: August 26, 2005
By Richard G. Baldwin
File: FwlProj020.htm
This laboratory project was prepared specifically for the benefit of my students who are enrolled in ITNW 1351, Fundamentals of Wireless LANs.
The project was designed under the assumption that students enrolled in the course have successfully completed the prerequisite course, ITNW 1325, Fundamentals of Networking Technologies.
The project design also assumes that the students are actively studying the material in the prescribed textbook for this course, which explains such complex topics as the IEEE 802.11g wireless specification.
Another browser window
I recommend that you open another copy of this document in a separate browser window so that you can easily view the discussion and the figures at the same time.
An earlier laboratory project demonstrated that the Linksys router is ready to communicate (in an unsecured way) with the computers in your network, (which are equipped with IEEE 802.11g NICs) via wireless technology as soon as you take the router out of the box and apply power. However, that project only demonstrated communications between the router and the computers in the network, one computer at a time.
Communication among network computers
The purpose of this project is to demonstrate that the router also facilitates communication among the individual computers in the network.
File sharing
In particular, this project demonstrates the operation of a wireless LAN using file sharing among the computers in the network.
The following equipment is required to complete this laboratory project:
Computer A and Computer B
The text in this document will need to refer to two different computers. I will refer to the two computers as Computer A and Computer B.
Briefly, Computer A is a computer that shares its files across the network. Computer B is a computer that accesses the files that are shared across the network by Computer A.
Reset the router
You will begin by resetting the router to its factory default configuration.
Setup Computer A for file sharing
Then you will cause one of the computers in your network (Computer A) to create, populate, and share a folder named junk containing a text file named readme.txt.
Identify and save the computer name for Computer A
In the process of doing this, you will identify and save the network name for Computer A.
The network name for Computer A will be used later by Computer B as the mechanism by which Computer B finds Computer A on the network.
Make wireless connections to the router
Then you will cause both computers (Computer A and Computer B) to make a wireless connection to the router.
Find the computer that is sharing files
Finally, you will cause Computer B to search the network for Computer A. That search will be based on the network name for Computer A that was identified and saved earlier.
Access and display a shared file
Once Computer B finds Computer A on the network, you will cause Computer B to access and display the contents of a text file that is shared across the network by Computer A.
Disclaimer regarding file sharing
Unless file sharing is handled properly, the sharing of files across a network can open up security holes in the network.
The purpose of this project is not to teach you the proper way to share files. Rather, the purpose is to use file sharing to demonstrate that two or more computers can communicate with one another via the wireless router using wireless NICs.
The easiest way to share files
Therefore, the methodology that will be used to actually share the files in this project should not be taken as the best or safest way to share files. Rather the methodology is simply the easiest way to share files.
Learn before you share
Before you start sharing files on your network, you should study the subject and learn how to share files securely on your network.
Another course for another day
The topic of proper file sharing technique is a topic for another course on another day.
Reset the router
Apply power to the router. Then press the Reset button on the back panel of the router and hold it down for at least five seconds to assure that the router is reset to the factory configuration settings.
Get the computer name for Computer A
Open the Start menu on Computer A. Right-click on My Computer, and select Properties. This will display the System Properties dialog.
Open the tab entitled Computer Name. About half way down, you will see a line that reads something like the following:
Full computer name: ABCDEFG
Record the computer name
You will need it later to search the network for Computer A.
(There are a variety of other ways to get the computer name as well. Use whichever one you want to use so long as you get and save the network name of Computer A.)
Create and share a folder named junk
Create a new folder named junk on the C-Drive.
Create a file named readme.txt containing the text "I will share this file" and store it in the new folder named junk.
Right-click on the folder named junk and select Sharing and Security ...
Dialog to authorize file sharing
This will produce the dialog shown in Figure 1. As you can see, the dialog is opened to the tab that concerns sharing and security.
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Authorize file sharing without the wizard
Click the link near the bottom of the dialog that reads:
"If you understand the security risks but want to share files without running the wizard, click here."
This will produce the dialog shown in Figure 2 asking you to confirm your choice.
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Confirm your choice
Select "Just enable file sharing" and click the OK button.
You have now authorized the sharing of the folder (without using the wizard) but you haven't yet actually shared the folder.
Share the folder
Clicking the OK button in Figure 2 will produce the dialog shown in Figure 3.
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The dialog in Figure 3 is used to actually share a folder and to later rescind that sharing.
Execute the share
Check the box entitled "Share this folder on the network" in Figure 3 and click the OK button to actually execute the share.
Options are available
Note that you also have the option to allow, or not to allow users at other computers on the network to change the files contained in the shared folder.
Folder junk is now shared
The folder named junk is now available to other computers on the network.
The appearance of the file folder icon for the folder named junk, when viewed in Windows Explorer, changes to that shown in Figure 4.
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What is the shared folder icon?
Although it isn't obvious in Figure 4, the icon for a shared folder consists of a file folder in a human hand that appears to be handing the folder off to someone else.
Search the network for Computer A
Now that the folder has been shared by Computer A, it is accessible to the other computers on the network. Before those other computers can access that folder, however, they must locate Computer A and determine that the folder has been shared.
Open a Search window on Computer B
Open a Search window in Windows Explorer on Computer B by clicking the Search button at the top of a Windows Explorer window. This will produce a new window that looks something like that shown in Figure 5.
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The search window is divided into two panes.
Search for Computers or people
Select the link to "Computers or people" in the left pane in Figure 5.
Then select "A computer on the network" when asked what you are looking for.
This will produce the dialog shown in Figure 6.
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Specify the computer that you are searching for
Type the network name of Computer A into the text field labeled Computer name: and click the Search button.
Success!
After searching for awhile, the window should change to look something like Figure 7 with Computer A identified in the right pane.
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The results of the search
The item in the right pane in Figure 7 is the Computer description for the computer that matches the name of the computer that was searched for.
Stated differently, this is the Computer description for Computer A, which was located on the network by searching for that computer on the basis of its Computer name.
Open Computer A in Windows Explorer
Double-click on the Computer description in the right pane of Figure 7.
The window will change to look something like Figure 8.
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The junk folder on Computer A
The folder named junk that is showing in Figure 8 is a folder on Computer A. It is not a folder on Computer B where the Windows Explorer display actually appears.
Files in folder junk are accessible
At this point, the user of Computer B has access to all of the files in the folder named junk on Computer A just as though the folder resides on Computer B.
(However, accessing the files on Computer A may be slower than would be the case if the folder were actually located on Computer B.)
Access may be restricted
Further, as mentioned earlier in conjunction with Figure 3, the person sharing the folder from Computer A onto the network has several options, including the option to either allow or not allow other network users to change the files in the folder.
Therefore, it may not be possible for the user on Computer B to change the content of the files in the junk folder on Computer A, depending on the option selected by the user of Computer A when the folder was shared.
Open the junk folder and display readme.txt
When you open the folder named junk, you should see that it contains a file named readme.txt.
View the contents of that file in Notepad.
The contents of the file should read:
I will share this file.
Network computers can communicate with each other
The ability for one computer to read files contained in a shared folder on another computer demonstrates that the router is making it possible for the two computers to communicate with one another using their wireless NICs.
(There is another way to accomplish this by creating an ad hoc network that doesn't use a router or access point. That will be the topic of a future project.)
Copyright 2005, Richard G. Baldwin. Reproduction in whole or in part in any form or medium without express written permission from Richard Baldwin is prohibited.
Richard has participated in numerous consulting projects and he frequently provides onsite training at the high-tech companies located in and around Austin, Texas. He is the author of Baldwin's Programming Tutorials, which have gained a worldwide following among experienced and aspiring programmers. He has also published articles in JavaPro magazine.
In addition to his programming expertise, Richard has many years of practical experience in Digital Signal Processing (DSP). His first job after he earned his Bachelor's degree was doing DSP in the Seismic Research Department of Texas Instruments. (TI is still a world leader in DSP.) In the following years, he applied his programming and DSP expertise to other interesting areas including sonar and underwater acoustics.
Richard holds an MSEE degree from Southern Methodist University and has many years of experience in the application of computer technology to real-world problems.
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Figure 2 Sharing confirmation screen
Figure 3 Dialog to execute the share
Figure 4 Icon for a
shared folder
Figure 5 A WinXP search window
Figure 6 Computer search dialog
Figure 7 The search results
Figure 8 The folder named junk on Computer A