Hands on: File-sharing made easy

If you're starting out in networking and are having difficulty with file-sharing, this article can offer some solutions.

File-sharing is a fairly basic facility, built into the Windows operating system, but one that can be difficult to get working at times, despite all the wizards and other tools provided by Microsoft.

A common problem
The usual scenario is that you have a couple of Windows PCs and want to connect them to the internet via a shared router and, at the same time, share the odd file or two.

So, you fit suitable network interfaces – either wired or wireless – and attach the PCs to the router.

You use DHCP to assign IP addresses and are impressed with your abilities when, lo and behold, both PCs can browse the web. However, no matter what you try, you can’t share files.

You run the network setup wizard repeatedly, check all the connections, even phone a friend. But nothing works. So, what could be causing this? The PCs are clearly connected to the same network as they can both connect to the web via a common network router.

You may even have tried pinging one PC from the other and confirmed that they can see each other at the packet level.

You have probably then done a Google search and discovered that they need to be in the same Windows workgroup and made the changes required, making sure there are no spaces in the name if using an old version of Windows such as 98 or ME.

But even when you have redefined your network shares, the errors persist.

Not so common answers
Now, messages such as that shown above can be displayed for several reasons, including a lack of basic connectivity. However, once you’ve ruled that out, a little bit of lateral thinking is required, and desktop firewalls are a good place to start.

Your firewall could just be blocking the protocols that Windows uses to share files, so try turning it off for a while (on both PCs, of course, and with the internet disconnected) to see if the problem goes away.

If it doesn’t, then more investigation is required. If it does, you know that the problem is caused by the firewall and you can do something about it. If you’re using the firewall built into Windows XP, there’s a specific exception rule for file and printer sharing.

In fact, it’s usually activated for you when you run the network setup wizard, but can also be set manually. Go to the Control Panel and double-click the Windows Firewall icon. Click on the tab marked Exceptions. Then make sure there’s a tick alongside the entry marked File and Printer Sharing, and do the same on the other PC.

With a third-party firewall, you will need to find something similar or configure rules to allow traffic on the ports involved manually.

Access control
Having ruled out the firewall, the next suspect is the file-sharing software. In particular, the way that users are identified and authenticated.

When we all used Windows 95, 98 and ME, there was no such thing as a username or password; you just started the PC and were in. Moreover, the only security afforded to file sharing was password protection for individual shared folders.

When Windows NT and 2000 came along, however, you had to start logging on to your PC, and a new NTFS file system was added with access control lists (ACLs) to control access to shared folders and files based on your logon name and/or group membership.