Limiting number of connected clients

Ian - the linked rule is still trying to limit the number of connections per client. What I'm trying to do is limit the number of clients without limiting the connections per client. I'm not coming up with an elegant (or just quick) way to store a list of a fairly large (I'm using 1000 in my example) number of client_ip entries to check against to see if connections from that client are allowed and to not allow further clients once the quota is full.