How to do it...

1. In the folder bin, create a file called connection_handler.rs.

2. Add the following code and run it with cargo run --bin connection_handler:

1 use std::sync::{Arc, RwLock};
2 use std::net::Ipv6Addr;
3 use std::collections::HashMap;
4 use std::{thread, time};
5 use std::sync::atomic::{AtomicUsize, Ordering, ATOMIC_USIZE_INIT};
6 
7 // Client holds whatever state your client might have
8 struct Client {
9 ip: Ipv6Addr,
10 }
11 
12 // ConnectionHandler manages a list of connections
13 // in a parallelly safe way
14 struct ConnectionHandler {
15 // The clients are identified by a unique key
16 clients: RwLock<HashMap<usize, Client>>,
17 next_id: AtomicUsize,
18 }
19 
20 impl Client {
21 fn new(ip: Ipv6Addr) -> Self {
22 Client { ip }
23 }
24 }
25 
26 impl ConnectionHandler {
27 fn new() -> Self {
28 ConnectionHandler {
29 clients: RwLock::new(HashMap::new()),
30 next_id: ATOMIC_USIZE_INIT,
31 }
32 }
33 
34 fn client_count(&self) -> usize {
35 self.clients
36 .read()
37 .expect(&quot...