The URL is the address of the DataSocket server. The server program is a stand-alone program that handles connections and broadcasts data. You create a server by running the program that comes with LabVIEW. You publish to (write) and subscribe from (read) the server and both would use the same address. Normally the data is not file based but DataSocket does support file reads by specifying file or ftp instead of dstp in the URL. The server can be running on the same computer as a publisher/subscriber or on a different computer. NI is now offering a class called LabVIEW Networked Measurements that covers DataSocket. I strongly recomend it.