I am having a hard time understanding how the ident protocol works. I came across a summary of how it works at Wikipedia however don't quite follow what it means
The Ident Protocol is designed to work as a server daemon, on a user's computer, where it receives requests to a specified port, generally 113. In a query, a client specifies a pair of ports (a local and a remote port). The server will then send a specially designed response that identifies the username of the user who runs the program that uses the specified pair of ports.
For example I assume that every OS has an ident server running. If so where does it receive an ident request to a specified port? In that query it states the client specifies a part of ports? Which is the client and which is the server?