fix: bind/publish to different addresses in non linux (#425)

This makes:

* Linux bind to 127.0.0.1 and publish on 127.255.255.255 which allows
multiple listeners on the same port as expected.
* Windows bind and publish on 127.0.0.1, which also allows multiple
listeners.
* Mac's lo interface doesn't have `BROADCAST` enabled, so binding
multiple listeners is not supported since while we could allow binding
multiple listeners, only one of them would get the packets so instead we
err. Maybe there's a better way of doing this but in practice nobody's
going to be running multiple presentations at once so making this more
complicated provides no gain.

Cargo.toml

@@ -8,6 +8,7 @@ version = "0.9.0"
 edition = "2021"
 
 [dependencies]
+anyhow = "1"
 ansi-parser = "0.9"
 base64 = "0.22"
 bincode = "1.3"

src/commands/speaker_notes.rs

@@ -24,8 +24,11 @@ impl SpeakerNotesEventPublisher {
         // ignore unrelated events.
         let envelope = SpeakerNotesEventEnvelope { event, presentation_path: self.presentation_path.clone() };
         let data = serde_json::to_string(&envelope).expect("serialization failed");
-        self.socket.send(data.as_bytes())?;
-        Ok(())
+        match self.socket.send(data.as_bytes()) {
+            Ok(_) => Ok(()),
+            Err(e) if e.kind() == io::ErrorKind::ConnectionRefused => Ok(()),
+            Err(e) => Err(e),
+        }
     }
 }
 
@@ -38,6 +41,7 @@ impl SpeakerNotesEventListener {
     pub fn new(address: SocketAddr, presentation_path: PathBuf) -> io::Result<Self> {
         let s = Socket::new(Domain::IPV4, Type::DGRAM, Some(Protocol::UDP))?;
         // Use SO_REUSEADDR so we can have multiple listeners on the same port.
+        #[cfg(not(target_os = "macos"))]
         s.set_reuse_address(true)?;
         // Don't block so we can listen to the keyboard and this socket at the same time.
         s.set_nonblocking(true)?;
@@ -61,7 +65,7 @@ impl SpeakerNotesEventListener {
     }
 }
 
-#[derive(Clone, Debug, Serialize, Deserialize)]
+#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
 #[serde(tag = "command")]
 pub(crate) enum SpeakerNotesEvent {
     GoToSlide { slide: u32 },
@@ -73,3 +77,39 @@ struct SpeakerNotesEventEnvelope {
     presentation_path: PathBuf,
     event: SpeakerNotesEvent,
 }
+
+#[cfg(not(target_os = "macos"))]
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::config::{default_speaker_notes_listen_address, default_speaker_notes_publish_address};
+    use std::{thread::sleep, time::Duration};
+
+    fn make_listener(path: PathBuf) -> SpeakerNotesEventListener {
+        SpeakerNotesEventListener::new(default_speaker_notes_listen_address(), path).expect("building listener")
+    }
+
+    fn make_publisher(path: PathBuf) -> SpeakerNotesEventPublisher {
+        SpeakerNotesEventPublisher::new(default_speaker_notes_publish_address(), path).expect("building publisher")
+    }
+
+    #[test]
+    fn bind_multiple() {
+        let _l1 = make_listener("".into());
+        let _l2 = make_listener("".into());
+    }
+
+    #[test]
+    fn multicast() {
+        let path = PathBuf::from("/tmp/test.md");
+        let l1 = make_listener(path.clone());
+        let l2 = make_listener(path.clone());
+        let publisher = make_publisher(path);
+        let event = SpeakerNotesEvent::Exit;
+        publisher.send(event.clone()).expect("send failed");
+        sleep(Duration::from_millis(100));
+
+        assert_eq!(l1.try_recv().expect("recv first failed"), Some(event.clone()));
+        assert_eq!(l2.try_recv().expect("recv second failed"), Some(event));
+    }
+}

src/config.rs

@@ -393,11 +393,11 @@ impl Default for KeyBindingsConfig {
 #[serde(deny_unknown_fields)]
 pub struct SpeakerNotesConfig {
     /// The address in which to listen for speaker note events.
-    #[serde(default = "default_speaker_notes_address")]
+    #[serde(default = "default_speaker_notes_listen_address")]
     pub listen_address: SocketAddr,
 
     /// The address in which to publish speaker notes events.
-    #[serde(default = "default_speaker_notes_address")]
+    #[serde(default = "default_speaker_notes_publish_address")]
     pub publish_address: SocketAddr,
 
     /// Whether to always publish speaker notes.
@@ -408,8 +408,8 @@ pub struct SpeakerNotesConfig {
 impl Default for SpeakerNotesConfig {
     fn default() -> Self {
         Self {
-            listen_address: default_speaker_notes_address(),
-            publish_address: default_speaker_notes_address(),
+            listen_address: default_speaker_notes_listen_address(),
+            publish_address: default_speaker_notes_publish_address(),
             always_publish: false,
         }
     }
@@ -480,12 +480,22 @@ fn default_suspend_bindings() -> Vec<KeyBinding> {
 }
 
 #[cfg(target_os = "linux")]
-fn default_speaker_notes_address() -> SocketAddr {
+pub(crate) fn default_speaker_notes_listen_address() -> SocketAddr {
     SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 255, 255, 255)), 59418)
 }
 
 #[cfg(not(target_os = "linux"))]
-fn default_speaker_notes_address() -> SocketAddr {
+pub(crate) fn default_speaker_notes_listen_address() -> SocketAddr {
+    SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 59418)
+}
+
+#[cfg(not(target_os = "macos"))]
+pub(crate) fn default_speaker_notes_publish_address() -> SocketAddr {
+    SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 255, 255, 255)), 59418)
+}
+
+#[cfg(target_os = "macos")]
+pub(crate) fn default_speaker_notes_publish_address() -> SocketAddr {
     SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 59418)
 }
 

src/main.rs

@@ -15,6 +15,7 @@ use crate::{
     theme::{PresentationTheme, PresentationThemeSet},
     third_party::{ThirdPartyConfigs, ThirdPartyRender},
 };
+use anyhow::anyhow;
 use clap::{CommandFactory, Parser, error::ErrorKind};
 use commands::speaker_notes::{SpeakerNotesEventListener, SpeakerNotesEventPublisher};
 use comrak::Arena;
@@ -320,11 +321,13 @@ fn run(mut cli: Cli) -> Result<(), Box<dyn std::error::Error>> {
             .then(|| {
                 SpeakerNotesEventPublisher::new(config.speaker_notes.publish_address, full_presentation_path.clone())
             })
-            .transpose()?;
+            .transpose()
+            .map_err(|e| anyhow!("failed to create speaker notes publisher: {e}"))?;
         let events_listener = cli
             .listen_speaker_notes
             .then(|| SpeakerNotesEventListener::new(config.speaker_notes.listen_address, full_presentation_path))
-            .transpose()?;
+            .transpose()
+            .map_err(|e| anyhow!("failed to create speaker notes listener: {e}"))?;
         let command_listener = CommandListener::new(config.bindings.clone(), events_listener)?;
 
         options.print_modal_background = matches!(graphics_mode, GraphicsMode::Kitty { .. });