Let OS select random open port.

libloki/local_loki_server.js

@@ -54,7 +54,7 @@ class LocalLokiServer extends EventEmitter {
         if (err) {
           rej(err);
         } else {
-          res(port);
+          res(this.server.address().port);
         }
       });
     });
@@ -70,6 +70,14 @@ class LocalLokiServer extends EventEmitter {
 
     return Promise.resolve();
   }
+
+  getPort() {
+    if (this.server.listening) {
+      return this.server.address().port;
+    }
+
+    return null;
+  }
 }
 
 exports.LocalLokiServer = LocalLokiServer;

libtextsecure/message_receiver.js

@@ -84,7 +84,13 @@ MessageReceiver.prototype.extend({
 
     this.localServer.removeAllListeners();
     this.localServer.on('message', this.httpPollingResource.handleMessage);
-    this.localServer.start(8000);
+
+    // Passing 0 as the port will automatically assign an unused port
+    this.localServer
+      .start(0)
+      .then(port =>
+        window.log.info(`Local Server started at https://localhost:${port}`)
+      );
 
     // TODO: Rework this socket stuff to work with online messaging
     const useWebSocket = false;