Way to get list of clients

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I understand how to use rosservice or various ROS functions to get a list of services that have started. I know that it is not typically the way that clients work, but is there a way to get information on the service that a client is attempting to use, whether it be through the "call" or "wait_for_service" functions.

For example, I know that if a node starts a service, I can poll "getSystemState" through a separate node and get information on the service. I assume there is not a method, but is there an equivalent option for clients?