The core protocol and error codes, HTTP headers and perhaps the details of basic authentication.

What a network is, the core concepts of the IP protocol suite and the sockets API.How to start your application server and deploy a web application on it.What a web application is what a servlet is, where classes, libraries and data go in a web application.How to diagnose trouble from exception traces, what a NullPointerException (NPE) and other common exceptions are, and how to fix them.What a classloader is, what hierarchical classloaders are, and the common causes of a 'ClassNotFoundException'.What threads are, race conditions, thread safety and sychronization.Core Java datatypes, classes and programming concepts.

Things you need to know before writing a Web Service: While you can learn about SOAP as you go along, writing Axis clients and servers is not the right time to be learning foundational Java concepts, such as what an array is, or basic application server concepts such as how servlets work, and the basics of the HTTP protocol. A lot of problems with Axis are encountered by people who are new to Java, server-side Java and SOAP.

Apache tomcat 8 setup