diff --git a/media/java/android/media/Controller2Link.java b/media/java/android/media/Controller2Link.java
index d6a6e1442fa5f..77e96b95ac1a1 100644
--- a/media/java/android/media/Controller2Link.java
+++ b/media/java/android/media/Controller2Link.java
@@ -21,6 +21,8 @@ import android.os.Parcel;
 import android.os.Parcelable;
 import android.os.RemoteException;
 
+import java.util.Objects;
+
 /**
  * Handles incoming commands from {@link MediaSession2} and {@link MediaLibrarySession}
  * to both {@link MediaController2} and {@link MediaBrowser2}.
@@ -68,6 +70,20 @@ public final class Controller2Link implements Parcelable {
         dest.writeStrongBinder(mIController.asBinder());
     }
 
+    @Override
+    public int hashCode() {
+        return mIController.asBinder().hashCode();
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (!(obj instanceof Controller2Link)) {
+            return false;
+        }
+        Controller2Link other = (Controller2Link) obj;
+        return Objects.equals(mIController.asBinder(), other.mIController.asBinder());
+    }
+
     /** Interface method for IMediaController2.notifyConnected */
     public void notifyConnected(int seq, Bundle connectionResult) {
         try {
diff --git a/media/java/android/media/MediaController2.java b/media/java/android/media/MediaController2.java
index 6a089ecc59eab..3894e75630d0b 100644
--- a/media/java/android/media/MediaController2.java
+++ b/media/java/android/media/MediaController2.java
@@ -98,7 +98,6 @@ public class MediaController2 implements AutoCloseable {
 
         mNextSeqNumber = 0;
 
-        Session2Link sessionBinder = token.getSessionLink();
         if (token.getType() == TYPE_SESSION) {
             connectToSession();
         } else {
@@ -120,9 +119,11 @@ public class MediaController2 implements AutoCloseable {
             mCallbackExecutor.execute(() -> {
                 mCallback.onDisconnected(MediaController2.this);
             });
+            mSessionBinder = null;
         }
     }
 
+    // Called by Controller2Link.onConnected
     void onConnected(int seq, Bundle connectionResult) {
         final long token = Binder.clearCallingIdentity();
         try {
@@ -155,10 +156,18 @@ public class MediaController2 implements AutoCloseable {
         }
     }
 
+    // Called by Controller2Link.onDisconnected
     void onDisconnected(int seq) {
-        // TODO: Implement this
+        final long token = Binder.clearCallingIdentity();
+        try {
+            // close() will call mCallback.onDisconnected
+            close();
+        } finally {
+            Binder.restoreCallingIdentity(token);
+        }
     }
 
+    // Called by Controller2Link.onSessionCommand
     void onSessionCommand(int seq, Session2Command command, Bundle args) {
         // TODO: Implement this
     }
diff --git a/media/java/android/media/MediaSession2.java b/media/java/android/media/MediaSession2.java
index 4ef5810471ee5..52e607d07f85c 100644
--- a/media/java/android/media/MediaSession2.java
+++ b/media/java/android/media/MediaSession2.java
@@ -35,6 +35,7 @@ import android.os.Process;
 import android.util.Log;
 
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -107,7 +108,13 @@ public class MediaSession2 implements AutoCloseable {
             synchronized (MediaSession2.class) {
                 SESSION_ID_LIST.remove(mSessionId);
             }
-            // TODO: Implement this
+            Collection<ControllerInfo> controllerInfos;
+            synchronized (mLock) {
+                controllerInfos = mConnectedControllers.values();
+            }
+            for (ControllerInfo info : controllerInfos) {
+                info.notifyDisconnected();
+            }
         } catch (Exception e) {
             // Should not be here.
         }
@@ -118,6 +125,7 @@ public class MediaSession2 implements AutoCloseable {
         return true;
     }
 
+    // Called by Session2Link.onConnect
     void onConnect(final Controller2Link controller, int seq, Bundle connectionRequest) {
         if (controller == null || connectionRequest == null) {
             return;
@@ -173,21 +181,12 @@ public class MediaSession2 implements AutoCloseable {
                     if (isClosed()) {
                         return;
                     }
-                    try {
-                        controller.notifyConnected(
-                                controllerInfo.mNextSeqNumber++, connectionResult);
-                    } catch (RuntimeException e) {
-                        // Controller may be died prematurely.
-                    }
+                    controllerInfo.notifyConnected(connectionResult);
                 } else {
                     if (DEBUG) {
                         Log.d(TAG, "Rejecting connection, controllerInfo=" + controllerInfo);
                     }
-                    try {
-                        controller.notifyDisconnected(controllerInfo.mNextSeqNumber++);
-                    } catch (RuntimeException e) {
-                        // Controller may be died prematurely.
-                    }
+                    controllerInfo.notifyDisconnected();
                 }
             });
         } finally {
@@ -195,20 +194,24 @@ public class MediaSession2 implements AutoCloseable {
         }
     }
 
+    // Called by Session2Link.onDisconnect
     void onDisconnect(final Controller2Link controller, int seq) {
         if (controller == null) {
             return;
         }
+        final ControllerInfo controllerInfo;
+        synchronized (mLock) {
+            controllerInfo = mConnectedControllers.get(controller);
+        }
+        if (controllerInfo == null) {
+            return;
+        }
+
         final long token = Binder.clearCallingIdentity();
         try {
             synchronized (mLock) {
-                final ControllerInfo controllerInfo = mConnectedControllers.get(controller);
                 mCallbackExecutor.execute(() -> {
-                    try {
-                        controller.notifyDisconnected(controllerInfo.mNextSeqNumber++);
-                    } catch (RuntimeException e) {
-                        // Controller may be died prematurely.
-                    }
+                    mCallback.onDisconnected(MediaSession2.this, controllerInfo);
                 });
                 mConnectedControllers.remove(controller);
             }
@@ -217,6 +220,7 @@ public class MediaSession2 implements AutoCloseable {
         }
     }
 
+    // Called by Session2Link.onSessionCommand
     void onSessionCommand(final Controller2Link controller, final int seq,
             final Session2Command command, final Bundle args) {
         // TODO: Implement this
@@ -323,13 +327,12 @@ public class MediaSession2 implements AutoCloseable {
      * <p>
      * This API is not generally intended for third party application developers.
      */
-    public static final class ControllerInfo {
+    static final class ControllerInfo {
         private final RemoteUserInfo mRemoteUserInfo;
         private final boolean mIsTrusted;
         private final Controller2Link mControllerBinder;
+        private int mNextSeqNumber;
 
-        @SuppressWarnings("WeakerAccess") /* synthetic access */
-        int mNextSeqNumber;
         @SuppressWarnings("WeakerAccess") /* synthetic access */
         Session2CommandGroup mAllowedCommands;
 
@@ -348,7 +351,7 @@ public class MediaSession2 implements AutoCloseable {
         }
 
         /**
-         * @hide
+         * @return remote user info of the controller.
          */
         @NonNull
         public RemoteUserInfo getRemoteUserInfo() {
@@ -370,6 +373,36 @@ public class MediaSession2 implements AutoCloseable {
             return mRemoteUserInfo.getUid();
         }
 
+        public void notifyConnected(Bundle connectionResult) {
+            if (mControllerBinder != null) {
+                try {
+                    mControllerBinder.notifyConnected(getNextSeqNumber(), connectionResult);
+                } catch (RuntimeException e) {
+                    // Controller may be died prematurely.
+                }
+            }
+        }
+
+        public void notifyDisconnected() {
+            if (mControllerBinder != null) {
+                try {
+                    mControllerBinder.notifyDisconnected(getNextSeqNumber());
+                } catch (RuntimeException e) {
+                    // Controller may be died prematurely.
+                }
+            }
+        }
+
+        public void sendSessionCommand(Session2Command command, Bundle args) {
+            if (mControllerBinder != null) {
+                try {
+                    mControllerBinder.sendSessionCommand(getNextSeqNumber(), command, args);
+                } catch (RuntimeException e) {
+                    // Controller may be died prematurely.
+                }
+            }
+        }
+
         /**
          * Return if the controller has granted {@code android.permission.MEDIA_CONTENT_CONTROL} or
          * has a enabled notification listener so can be trusted to accept connection and incoming
@@ -407,6 +440,10 @@ public class MediaSession2 implements AutoCloseable {
             return "ControllerInfo {pkg=" + mRemoteUserInfo.getPackageName() + ", uid="
                     + mRemoteUserInfo.getUid() + ", allowedCommands=" + mAllowedCommands + "})";
         }
+
+        private synchronized int getNextSeqNumber() {
+            return mNextSeqNumber++;
+        }
     }
 
     /**