In software development these days, networks are all-important. For example, Sun Microsystems uses the slogan, "the network is the computer." IBM promotes a network-based business model called "e-business." It's taken for granted that programs talk to each other across the network. But just how do they do it? Surprisingly, a technology that is more than 15 years old still provides the foundation for most of today's connectivity at the application level. This technology is based on an idea called sockets.