You want to make sure that a set of servers only accepts traffic for specific network services. You have verified that the servers are only running the necessary services, but you also want to make sure that the servers do not accept packets sent to those services. Which tool should you use

Port scanner.

Explanation:

A server can be defined as a specialized computer system that provides specific services for its clients on request. An example is a web server.

A web server is a type of computer that run websites and distribute web pages as they requested over the internet by end users (clients). When an end user request for a website by adding or typing the uniform resource locator (URL) on the address bar of a web browser, a request is sent to the internet to view the corresponding web pages (website) associated with that particular address.

In this scenario, the tool you should use is a port scanner because it would scan all packets that are sent or received by the server i.e all packets that are being transmitted to and from the server.