MacOS – How to get client Mac to use caching facility from Mac OS X Server on Yosemite

You should not use the Web proxy, but to use the Automatic Proxy Configuration, and setup a .pac file. In this file, you specify which domain/hosts you want the proxy.

Check wiki, http://en.wikipedia.org/wiki/Proxy_auto-config, for more information.

A sample may looks like:

function FindProxyForURL(url, host) 
{
  PROXY = "PROXY 127.0.0.1:8000";
  DEFAULT = "DIRECT";

  var domain_list = [
    "blahblahblah.com"
  ];

  for (var i = domain_list.length - 1; i >= 0; i--){
    if (dnsDomainIs(host,domain_list[i])) {return PROXY}
  };
}

The other simple way is to use the Firefox, and install an extension, Autoproxy.

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.