There are plenty of examples of GSD devices that are written using the Ruby editor built into the web admin.
The original Insteon PLM driver (#1932 I believe), is written in GSD and you can see the code there. The code for it can be used in a new device template for the EZServe, you would cut and paste that in, and tweak as needed. However, instead of using Com Port on PC in the device data section, you would add a TCP Port device data, and define it. GSD would know then to open a TCP socket instead. You can see an example of this in the Panasonic IP Camera template.
Also, for C++ Development, you can look on the wiki, for "Developing a DCE Device" ... and there are wiki pages on the GSD (Generic Serial Device) and writing devices in Ruby.