Return a new instance of the command. Make sure to return an instance of the command-specific subclass if it exists.

Keep a list of the subclasses.

Return true if this action returns matching events that we will not wait on, but can access at a later time.

Return true if this packet completes the command, i.e., there is no more synchronous response data to receive for this command.

Return true if this packet completes the matching asynchronous events for this command.

Actions of the form "Response: <Action> results will follow"

Virtually all commands return a response. There is at least one exception, handled with a command-specific subclass.

Return true if this is an ‘immediate’ command, i.e., it returns raw results synchronously without a response header. Don‘t bother doing this in subclasses. It is easy enough.

Return true if the packet should be included in the response. Raw and synchronous responses are kept. Some event responses are rejected.

By default, we keep any event packet, unless it is the completion packet for a ‘follows’ command. These are just marker packets that signify the end of the event stream for the response. TODO: They do contain a count of the events generated, which perhaps we want to verify matches the number we think we have received?

Return true if this action will return matching events that we will wait on.