Galvin Edition 9 Exercise 5 Question 21 (Page No. 247)

Question

Servers can be designed to limit the number of open connections. For example, a server may wish to have only N socket connections at any point in time. As soon as N connections are made, the server will not accept another incoming connection until an existing connection is released. Explain how semaphores can be used by a server to limit the number of concurrent connections.

Comments

Server process may look like

S = n; // maximum number of request that can be handled by server
mutex = 1;   
Server() {
    while(true) {
        wait(S);
        wait(mutex);
        
            Critical Section
        
        signal(mutex);
        signal(S);
    }
}

Once more than n number of request arrive, server will suspend their request, but as soon as existing connection is released server will be able to accept new connections.