QuickFIX comes with several example applications. These application are in the quickfix/examples directory. These applications are not meant to demonstrate good application design or meant to be used in a real production system. They are merely provided as a tutorial on how to build an application with QuickFIX.
The applications provided are ordermatch which is a c++ server that will match and execute limit orders, and tradeclient is a little c++ console based trading client. Banzai is a Java GUI based trading client. Finally there is executor. Executor is a server that simply fills every limit order that it receives. Executor has been implemented in C++, Java, C#, VB.NET, Python and Ruby. This is a great example for demonstrating how to do the same things in all of QuickFIX's supported API's.
Please study these examples to see a complete although minimal implementation of a FIX application.