Number of user connections and user IDs in MS SQL 7

What is the best way to:

1) Track the number of user connections to SQL Server (disregarding any
connections SQL Server may initiate itself)

and

2) Assign a unique sequential (1..N) ID to each user as they login, and
remove that ID, making it available for the next user, as they log out?

We are using Delphi 5 Enterprise and MS SQL Server 7.

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