wip(inventory-agent): local presence advertisement and discovery using mdns almost working

harmony_inventory_agent/src/local_presence/discover.rs

@@ -0,0 +1,34 @@
+use mdns_sd::{ServiceDaemon, ServiceEvent};
+
+use crate::local_presence::SERVICE_NAME;
+
+pub type DiscoveryEvent = ServiceEvent;
+
+pub fn discover_agents(timeout: Option<u64>, on_event: fn(&DiscoveryEvent)) {
+    // Create a new mDNS daemon.
+    let mdns = ServiceDaemon::new().expect("Failed to create mDNS daemon");
+
+    // Start browsing for the service type.
+    // The receiver will be a stream of events.
+    let receiver = mdns.browse(SERVICE_NAME).expect("Failed to browse");
+
+    std::thread::spawn(move || {
+        while let Ok(event) = receiver.recv() {
+            on_event(&event);
+            match event {
+                ServiceEvent::ServiceData(resolved) => {
+                    println!("Resolved a new service: {}", resolved.fullname);
+                }
+                other_event => {
+                    println!("Received other event: {:?}", &other_event);
+                }
+            }
+        }
+    });
+
+    if let Some(timeout) = timeout {
+    // Gracefully shutdown the daemon.
+    std::thread::sleep(std::time::Duration::from_secs(timeout));
+    mdns.shutdown().unwrap();
+    }
+}