How do I send an arduino PIN state to a local PC using the ethernet connection?
The simplest method is to set up a web server on your PC.  You haven't mentioned what OS you run (which is kind of critical), so looking into WAMP or LAMP ("Windows/Apache/MySQL/PHP", or "Linux/Apache/MySQL/PHP") is probably your best option.

Once you have a working web server you can pretty much use verbatim the Ethernet examples for connecting to a remote website ("Web Client").  That website would be your local PC address, and you send whatever parameters you want.

You then write a small PHP script (or whatever language you program your chosen web server in) to accept that web request and process it accordingly.

In general you never need to explicitly send the IP address since it is encapsulated as part of the actual socket connection information and is generally made available through various means to your web page (see $_SERVER in PHP for example).

If you want to get more "low level" and lighter weight then you would most likely be looking at writing a UDP server on your computer which receives UDP requests from the Arduinos and processes them as needed.  The content of a UDP request is entirely up to you, but programming a server for dealing with it is beyond the scope of an answer here - suffice it to say there are plenty of resources online available for all the major operating systems and programming languages on how to write UDP servers.