What functions do the servants perform in the plot of The Rivals?

In The Rivals we have a vestige of the stock servants of classical come­
dy, who acted as foils to their masters, as messengers and go­betweens in
their love affairs, and as confidants as well.
In the opening scene of The Rivals the servants are used to give us
information about the main characters. Thus we learn that Sir Anthony
Absolute has brought Julia Melville to Bath and is gouty (and therefore,
bad­tempered), and that Sir Anthony's son, Captain Jack Absolute, is
pretending to be Ensign Beverley, because he is in love with the rich
Lydia Languish, who is likely to like him better as a half­pay ensign than
as heir to Sir Anthony. We also hear of Mrs Malaprop as a `tough old
aunt' and learn that Faulkland is engaged to Julia Melville, and that Jack
is bribing Lucy, Lydia's maid. Apart from this information about the
main characters (excluding Bob Acres and Sir Lucius O'Trigger), Bath is
described from the servants' point of view.
In the second scene ...