Add autodiscovery for Jellyfin servers (#1146)

* Add autodiscovery for Jellyfin servers

* Remove debugging aids

you didn't see anything

* Fix linter errors

* Send a discovery packet to localhost too

src/main/features/core/autodiscover/index.ts

@@ -0,0 +1,55 @@
+import { createSocket } from 'dgram';
+import { ipcMain } from 'electron';
+
+import { DiscoveredServerItem, ServerType } from '/@/shared/types/types';
+
+type JellyfinResponse = {
+    Address: string;
+    Id: string;
+    Name: string;
+};
+
+function discoverAll(reply: (server: DiscoveredServerItem) => void) {
+    return Promise.all([discoverJellyfin(reply)]);
+}
+
+function discoverJellyfin(reply: (server: DiscoveredServerItem) => void) {
+    const sock = createSocket('udp4');
+    sock.on('message', (msg) => {
+        try {
+            const response: JellyfinResponse = JSON.parse(msg.toString('utf-8'));
+
+            reply({
+                name: response.Name,
+                type: ServerType.JELLYFIN,
+                url: response.Address,
+            });
+        } catch (e) {
+            // Got a spurious response, ignore?
+            console.error(e);
+        }
+    });
+
+    sock.bind(() => {
+        sock.setBroadcast(true);
+        // Send a broadcast packet to both loopback and default route, allowing discovery of same-machine instances
+        sock.send('who is JellyfinServer?', 7359, '127.255.255.255');
+        sock.send('who is JellyfinServer?', 7359, '255.255.255.255');
+    });
+
+    return new Promise<void>((resolve) => {
+        setTimeout(() => {
+            sock.close();
+            resolve();
+        }, 3000);
+    });
+}
+
+ipcMain.on('autodiscover-ping', (ev) => {
+    if (ev.ports.length === 0) throw new Error('Expected a port to stream autodiscovery results');
+    const port = ev.ports[0];
+
+    discoverAll((result) => port.postMessage(result))
+        .then(() => port.close())
+        .catch((err) => console.error(err));
+});

src/main/features/core/index.ts

@@ -1,3 +1,4 @@
+import './autodiscover';
 import './lyrics';
 import './player';
 import './remote';