As part of the apprenticeship at 8th Light, all apprentices are required to build a web server that passes a suite of tests known as cob_spec via FitNesse. Some apprentices have written the server in Clojure, while most write it in Java. Theoretically, the server could be written in any Turing complete language, however Java has vast resources built into its many libraries that make building a server more accessible.

According to Elliotte Harold in his book Java Network Programming, Java is the first programming language designed from the ground up with networking in mind, and it is easy for Java applications to send and receive data across the Internet. I find it important to fully understand the underlying concepts because they provide a backbone for e-commerce, collaborative computing, and global communication. In addition, without the power of networked applications I would most likely not be getting paid to do the learning and work that is currently supporting my livelihood.

The first concept to grapple with is that of sockets. A socket is simply one endpoint of a two-way communication link between two programs running on a network. What is an endpoint, you ask? An endpoint is the combination of an IP address and a port number. And a port number? That identifies the specific channel upon which a socket can communicate. Having multiple ports is necessary so that a computer can send and receive information that pertains to more than one operation at a time.

So back to sockets. The java.net class has a system-independent implementation of the server side of a client/server socket connection called ServerSocket. Whew, that was a mouthful. That basically means that the code can be executed to turn pretty much any computer running it into a server. In my next post, I will go into further depth as to how to use this class, and others related to it, to begin constructing a basic server in Java. I will also delve into HTTP and the how the various components of that protocol function. Look forward to more posts about networking and Java!