Netcat utility worth a look

My company wants to block access to some Internet sites but it doesn't have the funds to buy a proxy server. We 're thinking about just writing one. Could you give me some direction?

Greg Chu, vice president of technology,

DelNet

You can build a Web proxy server quickly using netcat, a public domain C program available at ftp://coast.cs.purdue.edu/pub/ tools/unix/netcat. This great utility is my network vice grip. It builds out of the box on just about every Unix variant, and only takes a bit of work to compile under Windows.

For your mission, you 'll have to compile a list of sites to block and connect that list to netcat. While adding the list to the proxy server is straightforward, putting together and maintaining the list of sites requires some real work. My hunch is that the effort would quickly surpass the price of a commercial proxy server.

On the other hand, netcat is a must read. It 's simply the most entertaining piece of useful source code I 've ever seen. The netcat home site is at www.avian.org.

I'm trying to build a virtual private network (VPN) that will link 14 remote offices to our home office. Our ISP cannot provide different IP addresses for the gateway and the router so we can access them as required. Can you help us?

John Auldridge, chief operating officer,

Dental One

To be blunt, your ISP should be able to provide you with the IP addresses you need for a 15-site VPN. If the ISP can't, it 's either too small to support your needs or so big that it doesn't care about your business.

Now it might be possible to achieve your goals through some imaginative uses of network address translation and port mapping using the IP addresses that you do have. However, I 'm not sure it would be worth the trouble since the marketplace is full of ISPs competing for multisite customers.

Actually, you shouldn't even need to have all the offices served by the same ISP - that flexibility is, after all, the attraction of sending private communications over the public Internet.