fix: Allow multiple dispatch instances to work

Avahi names can't be the same. Add random suffix to the
service name by default (-<4 hex digits>). Add two new
command line options:

    --no-avahi-random (no suffix)
    --avahi-suffix <suffix>

The two options are mutually exclusive.

Resolves: #4

Author: markg-github

Cargo.toml

@@ -23,6 +23,7 @@ zbus = { version = "5.11", default-features = false, features = ["tokio"] }
 http-body-util = { version = "0.1", default-features = false }
 serde_json = { version = "1.0", default-features = false }
 anyhow = { version = "1.0", default-features = false }
+rand = { version = "0.8", default-features = false, features = ["std", "std_rng"] }
 
 [build-dependencies]
 uefi-reset = { version = "1.0", artifact = "bin", target = "x86_64-unknown-uefi" }

src/avahi.rs

@@ -69,7 +69,11 @@ impl AvahiService {
 
     /// Register an HTTP service
     pub async fn register(&self, name: &str, port: u16, txt: &[(&str, &str)]) -> Result<()> {
-        let service_type = format!("_{name}._tcp");
+        // Service type should be the fixed dispatch service type (based on the
+        // package name). The `name` parameter is the instance/display name
+        // and may not match CARGO_PKG_NAME anymore;
+        // beacon browses for the fixed service type.
+        let service_type = format!("_{}._tcp", std::env!("CARGO_PKG_NAME"));
 
         // Convert TXT records to the format expected by Avahi
         let txt: Vec<Vec<u8>> = txt

src/main.rs

@@ -44,6 +44,14 @@ struct Args {
     /// Path to offer services on
     #[arg(short = 'p', long, default_value = concat!("/", std::env!("CARGO_PKG_NAME")))]
     path: String,
+
+    /// Disable random suffix of the Avahi service name, ie, disable default behavior
+    #[arg(long, conflicts_with = "avahi_suffix")]
+    no_avahi_random: bool,
+
+    /// Add a custom suffix to the Avahi service name (e.g., dispatch-mytest)
+    #[arg(long, conflicts_with = "no_avahi_random")]
+    avahi_suffix: Option<String>,
 }
 
 #[tokio::main]
@@ -72,8 +80,18 @@ async fn main() -> Result<()> {
     // Create the HTTP server
     let server = Server::new(listener, status.clone(), github, path.clone())?;
 
-    // Create TXT records
-    let name = std::env!("CARGO_PKG_NAME");
+    // Build Avahi service name based on command line options
+    // Clients browse by service type (_dispatch._tcp), not instance name
+    let base = std::env!("CARGO_PKG_NAME");
+    let name = if let Some(ref suffix) = args.avahi_suffix {
+        format!("{base}-{suffix}")
+    } else if !args.no_avahi_random {
+        let random_suffix: u16 = rand::random();
+        format!("{base}-{random_suffix:04x}")
+    } else {
+        base.to_string()
+    };
+
     let txt = [
         ("description", std::env!("CARGO_PKG_DESCRIPTION")),
         ("version", std::env!("CARGO_PKG_VERSION")),
@@ -82,7 +100,7 @@ async fn main() -> Result<()> {
 
     // Start the Avahi service discovery.
     let avahi = AvahiService::new().await?;
-    avahi.register(name, addr.port(), &txt).await?;
+    avahi.register(name.as_str(), addr.port(), &txt).await?;
 
     // Create event stream for terminal events
     let mut events = EventStream::new();