Make Service Server Work

lib/core/service.dart

@@ -25,7 +25,7 @@ class Service {
   String type;
 
   /// Advertiser that is listened to for service requests when advertising.
-  Stream _advertiser;
+  StreamSubscription _advertiser;
 
   /// Checks whether or not the service is currently advertising.
   bool get isAdvertised => _advertiser != null;
@@ -70,16 +70,18 @@ class Service {
     // Listen for requests, forward them to the handler and then
     // send the response back to the ROS node.
     _advertiser = ros.stream
-        .where((message) => message['service'] == name)
+        .where((message) =>
+            message['service'] == name && message['op'] == 'call_service')
         .asyncMap((req) => handler(req['args']).then((resp) {
               ros.send(Request(
                 op: 'service_response',
-                id: req.id,
+                id: req['id'],
                 service: name,
                 values: resp ?? {},
                 result: resp != null,
               ));
-            }));
+            }))
+        .listen(null);
   }
 
   // Stop advertising the service.
@@ -89,6 +91,7 @@ class Service {
       op: 'unadvertise_service',
       service: name,
     ));
+    _advertiser?.cancel();
     _advertiser = null;
   }
 }

test/roslib_test.dart

@@ -71,6 +71,25 @@ void main() {
     expect(resp, {'sum': 3});
   });
 
+  test('host a service', () async {
+    final server = Service(
+      ros: ros,
+      name: '/add_two_ints_dart',
+      type: 'rospy_tutorials/AddTwoInts',
+    );
+    server.advertise((request) async {
+      return {'sum': request['a'] + request['b']};
+    });
+    final client = Service(
+      ros: ros,
+      name: '/add_two_ints_dart',
+      type: 'rospy_tutorials/AddTwoInts',
+    );
+    final req = {'a': 1, 'b': 2};
+    final resp = await client.call(req);
+    expect(resp, {'sum': 3});
+  });
+
   test('get and set a param value', () async {
     final param = Param(
       ros: ros,