OS X Server (Mavericks) requires wired network connection for Caching?
Via this Apple kbase article:

You can specify advanced configuration settings for the Caching service with the command line or by editing /Library/Server/Caching/Config/Config.plist.
Interface | Listen on all interfaces |    The BSD name of a network interface to be used by the Caching service.
Setting values for a key
To set a key with a simple value, you can use the serveradmin(8) command. For example, to set the Interface key to en1, you would execute this command as an administrator:
sudo serveradmin settings caching:Interface = en1

I am unable to find any evidence anywhere that Server can use wireless interfaces, but if you connect a USB to Ethernet Adapter and use its interface number in the line above you should be able to use Caching Server.