first untested and finalized code snippets to support agent push on the agent side.

Author: 9SMTM6

host_agent/src/install/mod.rs

@@ -10,7 +10,6 @@ use core::fmt;
 use shuthost_common::generate_secret;
 #[cfg(target_os = "linux")]
 use shuthost_common::{is_openrc, is_systemd};
-use std::net::UdpSocket;
 use std::process::Command;
 
 use crate::{DEFAULT_PORT, registration, server::get_default_shutdown_command};
@@ -435,12 +434,7 @@ pub(crate) fn get_hostname() -> Option<String> {
 
 /// Tests Wake-on-LAN packet reachability by listening and echoing back packets.
 pub(crate) fn test_wol_reachability(port: u16) -> Result<(), String> {
-    let socket = UdpSocket::bind(format!("0.0.0.0:{port}"))
-        .map_err(|e| format!("Failed to bind test socket: {e}"))?;
-
-    socket
-        .set_broadcast(true)
-        .map_err(|e| format!("Failed to set broadcast: {e}"))?;
+    let socket = crate::server::create_broadcast_socket(port)?;
 
     println!("Listening for WOL test packets on port {port}...");
 

host_agent/src/server.rs

@@ -8,7 +8,7 @@ use std::{
 
 use clap::Parser;
 use secrecy::SecretString;
-use shuthost_common::UnwrapToStringExt as _;
+use shuthost_common::{create_signed_message, UnwrapToStringExt as _};
 
 use crate::{
     commands::execute_shutdown,
@@ -50,6 +50,9 @@ pub(crate) fn start_host_agent(mut config: ServiceOptions) {
         TcpListener::bind(&addr).unwrap_or_else(|_| panic!("Failed to bind port {addr}"));
     println!("Listening on {addr}");
 
+    // Send UDP broadcast with signed announcement message
+    broadcast_startup(&config, port);
+
     for stream in listener.incoming() {
         match stream {
             Ok(stream) => {
@@ -72,6 +75,21 @@ pub(crate) fn start_host_agent(mut config: ServiceOptions) {
     }
 }
 
+fn broadcast_startup(config: &ServiceOptions, port: u16) {
+    let signed_message = create_signed_message("TBD needs some stable reference to the host, probably needs config update", config.shared_secret.as_ref().unwrap());
+    match create_broadcast_socket(0) {
+        Ok(socket) => {
+            let broadcast_addr = format!("255.255.255.255:{}", port);
+            if let Err(e) = socket.send_to(signed_message.as_bytes(), &broadcast_addr) {
+                eprintln!("Failed to send startup broadcast: {e}");
+            } else {
+                println!("Sent startup broadcast to {broadcast_addr}");
+            }
+        }
+        Err(e) => eprintln!("Failed to create broadcast socket: {e}"),
+    }
+}
+
 /// Handles a client connection: reads data, invokes handler, writes response, and triggers shutdown if needed.
 /// Returns the action to take after handling the request.
 fn handle_client(mut stream: TcpStream, config: &ServiceOptions) -> Action {
@@ -112,3 +130,15 @@ pub(crate) fn get_default_shutdown_command() -> String {
     #[cfg(target_os = "windows")]
     return "shutdown /s /t 0".to_string();
 }
+
+/// Creates a UDP socket configured for broadcasting on the specified port.
+///
+/// Binds to the given port on all interfaces and enables broadcasting.
+/// Returns the socket if successful, or an error message if binding or setting broadcast fails.
+pub(crate) fn create_broadcast_socket(port: u16) -> Result<std::net::UdpSocket, String> {
+    let socket = std::net::UdpSocket::bind(format!("0.0.0.0:{port}"))
+        .map_err(|e| format!("Failed to bind socket on port {port}: {e}"))?;
+    socket.set_broadcast(true)
+        .map_err(|e| format!("Failed to set broadcast on socket: {e}"))?;
+    Ok(socket)
+}