I found this issue on the official repository. But instead of an straight way is more an implementation from oakserver. https://github.com/denoland/deno/discussions/9314
You can cast the connection's address as a Deno.NetAddr and access the hostname (and port if you want) there:
const server = Deno.listen({ port: 8080 });
for await (const conn of server) {
(async () => {
const httpConn = Deno.serveHttp(conn);
const { hostname } = conn.remoteAddr as Deno.NetAddr;
for await (const requestEvent of httpConn) {
requestEvent.respondWith(new Response(hostname));
}
})();
}