Implement SMS application using CFSMS Event Gateway

After I did some readings on Coldfusion SMS Event Gateway.

I'm wondering whether I need an external SMS server or system for the SMS gateway in CF to work. Looking forward to get reply from you all.

The following is what I get from Adobe Coldfusion 8 livedocs:

"To Implement SMS application with ways below:

1.      Create a ColdFusion application that uses an instance of the SMSGateway class to communicate with one or more SMSCs.

2.      Use the SMS testing server and client simulator to test your application without requiring an outside SMS service provider."

Thanks in advance.