server/display/WifiDisplayController.java

/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.server.display;

import com.android.internal.util.DumpUtils;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.hardware.display.WifiDisplay;
import android.media.AudioManager;
import android.media.RemoteDisplay;
import android.net.NetworkInfo;
import android.net.wifi.p2p.WifiP2pConfig;
import android.net.wifi.p2p.WifiP2pDevice;
import android.net.wifi.p2p.WifiP2pDeviceList;
import android.net.wifi.p2p.WifiP2pGroup;
import android.net.wifi.p2p.WifiP2pManager;
import android.net.wifi.p2p.WifiP2pWfdInfo;
import android.net.wifi.p2p.WifiP2pManager.ActionListener;
import android.net.wifi.p2p.WifiP2pManager.Channel;
import android.net.wifi.p2p.WifiP2pManager.GroupInfoListener;
import android.net.wifi.p2p.WifiP2pManager.PeerListListener;
import android.os.Handler;
import android.util.Slog;
import android.view.Surface;

import java.io.PrintWriter;
import java.net.Inet4Address;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.util.ArrayList;
import java.util.Enumeration;

/**
 * Manages all of the various asynchronous interactions with the {@link WifiP2pManager}
 * on behalf of {@link WifiDisplayAdapter}.
 * <p>
 * This code is isolated from {@link WifiDisplayAdapter} so that we can avoid
 * accidentally introducing any deadlocks due to the display manager calling
 * outside of itself while holding its lock.  It's also way easier to write this
 * asynchronous code if we can assume that it is single-threaded.
 * </p><p>
 * The controller must be instantiated on the handler thread.
 * </p>
 */
final class WifiDisplayController implements DumpUtils.Dump {
    private static final String TAG = "WifiDisplayController";
    private static final boolean DEBUG = false;

    private static final int DEFAULT_CONTROL_PORT = 7236;
    private static final int MAX_THROUGHPUT = 50;
    private static final int CONNECTION_TIMEOUT_SECONDS = 30;
    private static final int RTSP_TIMEOUT_SECONDS = 15;

    private static final int DISCOVER_PEERS_MAX_RETRIES = 10;
    private static final int DISCOVER_PEERS_RETRY_DELAY_MILLIS = 500;

    private static final int CONNECT_MAX_RETRIES = 3;
    private static final int CONNECT_RETRY_DELAY_MILLIS = 500;

    // A unique token to identify the remote submix that is managed by Wifi display.
    // It must match what the media server uses when it starts recording the submix
    // for transmission.  We use 0 although the actual value is currently ignored.
    private static final int REMOTE_SUBMIX_ADDRESS = 0;

    private final Context mContext;
    private final Handler mHandler;
    private final Listener mListener;

    private final WifiP2pManager mWifiP2pManager;
    private final Channel mWifiP2pChannel;

    private final AudioManager mAudioManager;

    private boolean mWifiP2pEnabled;
    private boolean mWfdEnabled;
    private boolean mWfdEnabling;
    private NetworkInfo mNetworkInfo;

    private final ArrayList<WifiP2pDevice> mKnownWifiDisplayPeers =
            new ArrayList<WifiP2pDevice>();

    // True if there is a call to discoverPeers in progress.
    private boolean mDiscoverPeersInProgress;

    // Number of discover peers retries remaining.
    private int mDiscoverPeersRetriesLeft;

    // The device to which we want to connect, or null if we want to be disconnected.
    private WifiP2pDevice mDesiredDevice;

    // The device to which we are currently connecting, or null if we have already connected
    // or are not trying to connect.
    private WifiP2pDevice mConnectingDevice;

    // The device to which we are currently connected, which means we have an active P2P group.
    private WifiP2pDevice mConnectedDevice;

    // The group info obtained after connecting.
    private WifiP2pGroup mConnectedDeviceGroupInfo;

    // Number of connection retries remaining.
    private int mConnectionRetriesLeft;

    // The remote display that is listening on the connection.
    // Created after the Wifi P2P network is connected.
    private RemoteDisplay mRemoteDisplay;

    // The remote display interface.
    private String mRemoteDisplayInterface;

    // True if RTSP has connected.
    private boolean mRemoteDisplayConnected;

    // True if the remote submix is enabled.
    private boolean mRemoteSubmixOn;

    public WifiDisplayController(Context context, Handler handler, Listener listener) {
        mContext = context;
        mHandler = handler;
        mListener = listener;

        mWifiP2pManager = (WifiP2pManager)context.getSystemService(Context.WIFI_P2P_SERVICE);
        mWifiP2pChannel = mWifiP2pManager.initialize(context, handler.getLooper(), null);

        mAudioManager = (AudioManager)context.getSystemService(Context.AUDIO_SERVICE);

        IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction(WifiP2pManager.WIFI_P2P_STATE_CHANGED_ACTION);
        intentFilter.addAction(WifiP2pManager.WIFI_P2P_PEERS_CHANGED_ACTION);
        intentFilter.addAction(WifiP2pManager.WIFI_P2P_CONNECTION_CHANGED_ACTION);
        context.registerReceiver(mWifiP2pReceiver, intentFilter);
    }

    public void dump(PrintWriter pw) {
        pw.println("mWifiP2pEnabled=" + mWifiP2pEnabled);
        pw.println("mWfdEnabled=" + mWfdEnabled);
        pw.println("mWfdEnabling=" + mWfdEnabling);
        pw.println("mNetworkInfo=" + mNetworkInfo);
        pw.println("mDiscoverPeersInProgress=" + mDiscoverPeersInProgress);
        pw.println("mDiscoverPeersRetriesLeft=" + mDiscoverPeersRetriesLeft);
        pw.println("mDesiredDevice=" + describeWifiP2pDevice(mDesiredDevice));
        pw.println("mConnectingDisplay=" + describeWifiP2pDevice(mConnectingDevice));
        pw.println("mConnectedDevice=" + describeWifiP2pDevice(mConnectedDevice));
        pw.println("mConnectionRetriesLeft=" + mConnectionRetriesLeft);
        pw.println("mRemoteDisplay=" + mRemoteDisplay);
        pw.println("mRemoteDisplayInterface=" + mRemoteDisplayInterface);
        pw.println("mRemoteDisplayConnected=" + mRemoteDisplayConnected);
        pw.println("mRemoteSubmixOn=" + mRemoteSubmixOn);

        pw.println("mKnownWifiDisplayPeers: size=" + mKnownWifiDisplayPeers.size());
        for (WifiP2pDevice device : mKnownWifiDisplayPeers) {
            pw.println("  " + describeWifiP2pDevice(device));
        }
    }

    public void requestScan() {
        discoverPeers();
    }

    public void requestConnect(String address) {
        for (WifiP2pDevice device : mKnownWifiDisplayPeers) {
            if (device.deviceAddress.equals(address)) {
                connect(device);
            }
        }
    }

    public void requestDisconnect() {
        disconnect();
    }

    private void enableWfd() {
        if (!mWfdEnabled && !mWfdEnabling) {
            mWfdEnabling = true;

            WifiP2pWfdInfo wfdInfo = new WifiP2pWfdInfo();
            wfdInfo.setWfdEnabled(true);
            wfdInfo.setDeviceType(WifiP2pWfdInfo.WFD_SOURCE);
            wfdInfo.setSessionAvailable(true);
            wfdInfo.setControlPort(DEFAULT_CONTROL_PORT);
            wfdInfo.setMaxThroughput(MAX_THROUGHPUT);
            mWifiP2pManager.setWFDInfo(mWifiP2pChannel, wfdInfo, new ActionListener() {
                @Override
                public void onSuccess() {
                    if (DEBUG) {
                        Slog.d(TAG, "Successfully set WFD info.");
                    }
                    if (mWfdEnabling) {
                        mWfdEnabling = false;
                        setWfdEnabled(true);
                    }
                }

                @Override
                public void onFailure(int reason) {
                    if (DEBUG) {
                        Slog.d(TAG, "Failed to set WFD info with reason " + reason + ".");
                    }
                    mWfdEnabling = false;
                }
            });
        }
    }

    private void setWfdEnabled(final boolean enabled) {
        if (mWfdEnabled != enabled) {
            mWfdEnabled = enabled;
            mHandler.post(new Runnable() {
                @Override
                public void run() {
                    mListener.onEnablementChanged(enabled);
                }
            });
        }
    }

    private void discoverPeers() {
        if (!mDiscoverPeersInProgress) {
            mDiscoverPeersInProgress = true;
            mDiscoverPeersRetriesLeft = DISCOVER_PEERS_MAX_RETRIES;
            handleScanStarted();
            tryDiscoverPeers();
        }
    }

    private void tryDiscoverPeers() {
        mWifiP2pManager.discoverPeers(mWifiP2pChannel, new ActionListener() {
            @Override
            public void onSuccess() {
                if (DEBUG) {
                    Slog.d(TAG, "Discover peers succeeded.  Requesting peers now.");
                }

                mDiscoverPeersInProgress = false;
                requestPeers();
            }

            @Override
            public void onFailure(int reason) {
                if (DEBUG) {
                    Slog.d(TAG, "Discover peers failed with reason " + reason + ".");
                }

                if (mDiscoverPeersInProgress) {
                    if (reason == 0 && mDiscoverPeersRetriesLeft > 0 && mWfdEnabled) {
                        mHandler.postDelayed(new Runnable() {
                            @Override
                            public void run() {
                                if (mDiscoverPeersInProgress) {
                                    if (mDiscoverPeersRetriesLeft > 0 && mWfdEnabled) {
                                        mDiscoverPeersRetriesLeft -= 1;
                                        if (DEBUG) {
                                            Slog.d(TAG, "Retrying discovery.  Retries left: "
                                                    + mDiscoverPeersRetriesLeft);
                                        }
                                        tryDiscoverPeers();
                                    } else {
                                        handleScanFinished();
                                        mDiscoverPeersInProgress = false;
                                    }
                                }
                            }
                        }, DISCOVER_PEERS_RETRY_DELAY_MILLIS);
                    } else {
                        handleScanFinished();
                        mDiscoverPeersInProgress = false;
                    }
                }
            }
        });
    }

    private void requestPeers() {
        mWifiP2pManager.requestPeers(mWifiP2pChannel, new PeerListListener() {
            @Override
            public void onPeersAvailable(WifiP2pDeviceList peers) {
                if (DEBUG) {
                    Slog.d(TAG, "Received list of peers.");
                }

                mKnownWifiDisplayPeers.clear();
                for (WifiP2pDevice device : peers.getDeviceList()) {
                    if (DEBUG) {
                        Slog.d(TAG, "  " + describeWifiP2pDevice(device));
                    }

                    if (isWifiDisplay(device)) {
                        mKnownWifiDisplayPeers.add(device);
                    }
                }

                handleScanFinished();
            }
        });
    }

    private void handleScanStarted() {
        mHandler.post(new Runnable() {
            @Override
            public void run() {
                mListener.onScanStarted();
            }
        });
    }

    private void handleScanFinished() {
        final int count = mKnownWifiDisplayPeers.size();
        final WifiDisplay[] displays = WifiDisplay.CREATOR.newArray(count);
        for (int i = 0; i < count; i++) {
            displays[i] = createWifiDisplay(mKnownWifiDisplayPeers.get(i));
        }

        mHandler.post(new Runnable() {
            @Override
            public void run() {
                mListener.onScanFinished(displays);
            }
        });
    }

    private void connect(final WifiP2pDevice device) {
        if (mDesiredDevice != null
                && !mDesiredDevice.deviceAddress.equals(device.deviceAddress)) {
            if (DEBUG) {
                Slog.d(TAG, "connect: nothing to do, already connecting to "
                        + describeWifiP2pDevice(device));
            }
            return;
        }

        if (mConnectedDevice != null
                && !mConnectedDevice.deviceAddress.equals(device.deviceAddress)
                && mDesiredDevice == null) {
            if (DEBUG) {
                Slog.d(TAG, "connect: nothing to do, already connected to "
                        + describeWifiP2pDevice(device) + " and not part way through "
                        + "connecting to a different device.");
            }
            return;
        }

        mDesiredDevice = device;
        mConnectionRetriesLeft = CONNECT_MAX_RETRIES;
        updateConnection();
    }

    private void disconnect() {
        mDesiredDevice = null;
        updateConnection();
    }

    private void retryConnection() {
        if (mDesiredDevice != null && mConnectedDevice != mDesiredDevice
                && mConnectionRetriesLeft > 0) {
            mConnectionRetriesLeft -= 1;
            Slog.i(TAG, "Retrying Wifi display connection.  Retries left: "
                    + mConnectionRetriesLeft);

            // Cheap hack.  Make a new instance of the device object so that we
            // can distinguish it from the previous connection attempt.
            // This will cause us to tear everything down before we try again.
            mDesiredDevice = new WifiP2pDevice(mDesiredDevice);
            updateConnection();
        }
    }

    /**
     * This function is called repeatedly after each asynchronous operation
     * until all preconditions for the connection have been satisfied and the
     * connection is established (or not).
     */
    private void updateConnection() {
        // Step 1. Before we try to connect to a new device, tell the system we
        // have disconnected from the old one.
        if (mRemoteDisplay != null && mConnectedDevice != mDesiredDevice) {
            Slog.i(TAG, "Stopped listening for RTSP connection on " + mRemoteDisplayInterface
                    + " from Wifi display: " + mConnectedDevice.deviceName);

            mRemoteDisplay.dispose();
            mRemoteDisplay = null;
            mRemoteDisplayInterface = null;
            mRemoteDisplayConnected = false;
            mHandler.removeCallbacks(mRtspTimeout);

            setRemoteSubmixOn(false);

            mHandler.post(new Runnable() {
                @Override
                public void run() {
                    mListener.onDisplayDisconnected();
                }
            });

            // continue to next step
        }

        // Step 2. Before we try to connect to a new device, disconnect from the old one.
        if (mConnectedDevice != null && mConnectedDevice != mDesiredDevice) {
            Slog.i(TAG, "Disconnecting from Wifi display: " + mConnectedDevice.deviceName);

            final WifiP2pDevice oldDevice = mConnectedDevice;
            mWifiP2pManager.removeGroup(mWifiP2pChannel, new ActionListener() {
                @Override
                public void onSuccess() {
                    Slog.i(TAG, "Disconnected from Wifi display: " + oldDevice.deviceName);
                    next();
                }

                @Override
                public void onFailure(int reason) {
                    Slog.i(TAG, "Failed to disconnect from Wifi display: "
                            + oldDevice.deviceName + ", reason=" + reason);
                    next();
                }

                private void next() {
                    if (mConnectedDevice == oldDevice) {
                        mConnectedDevice = null;
                        updateConnection();
                    }
                }
            });
            return; // wait for asynchronous callback
        }

        // Step 3. Before we try to connect to a new device, stop trying to connect
        // to the old one.
        if (mConnectingDevice != null && mConnectingDevice != mDesiredDevice) {
            Slog.i(TAG, "Canceling connection to Wifi display: " + mConnectingDevice.deviceName);

            mHandler.removeCallbacks(mConnectionTimeout);

            final WifiP2pDevice oldDevice = mConnectingDevice;
            mWifiP2pManager.cancelConnect(mWifiP2pChannel, new ActionListener() {
                @Override
                public void onSuccess() {
                    Slog.i(TAG, "Canceled connection to Wifi display: " + oldDevice.deviceName);
                    next();
                }

                @Override
                public void onFailure(int reason) {
                    Slog.i(TAG, "Failed to cancel connection to Wifi display: "
                            + oldDevice.deviceName + ", reason=" + reason);
                    next();
                }

                private void next() {
                    if (mConnectingDevice == oldDevice) {
                        mConnectingDevice = null;
                        updateConnection();
                    }
                }
            });
            return; // wait for asynchronous callback
        }

        // Step 4. If we wanted to disconnect, then mission accomplished.
        if (mDesiredDevice == null) {
            return; // done
        }

        // Step 5. Try to connect.
        if (mConnectedDevice == null && mConnectingDevice == null) {
            Slog.i(TAG, "Connecting to Wifi display: " + mDesiredDevice.deviceName);

            mConnectingDevice = mDesiredDevice;
            WifiP2pConfig config = new WifiP2pConfig();
            config.deviceAddress = mConnectingDevice.deviceAddress;

            final WifiDisplay display = createWifiDisplay(mConnectingDevice);
            mHandler.post(new Runnable() {
                @Override
                public void run() {
                    mListener.onDisplayConnecting(display);
                }
            });

            final WifiP2pDevice newDevice = mDesiredDevice;
            mWifiP2pManager.connect(mWifiP2pChannel, config, new ActionListener() {
                @Override
                public void onSuccess() {
                    // The connection may not yet be established.  We still need to wait
                    // for WIFI_P2P_CONNECTION_CHANGED_ACTION.  However, we might never
                    // get that broadcast, so we register a timeout.
                    Slog.i(TAG, "Initiated connection to Wifi display: " + newDevice.deviceName);

                    mHandler.postDelayed(mConnectionTimeout, CONNECTION_TIMEOUT_SECONDS * 1000);
                }

                @Override
                public void onFailure(int reason) {
                    if (mConnectingDevice == newDevice) {
                        Slog.i(TAG, "Failed to initiate connection to Wifi display: "
                                + newDevice.deviceName + ", reason=" + reason);
                        mConnectingDevice = null;
                        handleConnectionFailure(false);
                    }
                }
            });
            return; // wait for asynchronous callback
        }

        // Step 6. Listen for incoming connections.
        if (mConnectedDevice != null && mRemoteDisplay == null) {
            Inet4Address addr = getInterfaceAddress(mConnectedDeviceGroupInfo);
            if (addr == null) {
                Slog.i(TAG, "Failed to get local interface address for communicating "
                        + "with Wifi display: " + mConnectedDevice.deviceName);
                handleConnectionFailure(false);
                return; // done
            }

            setRemoteSubmixOn(true);

            final WifiP2pDevice oldDevice = mConnectedDevice;
            final int port = getPortNumber(mConnectedDevice);
            final String iface = addr.getHostAddress() + ":" + port;
            mRemoteDisplayInterface = iface;

            Slog.i(TAG, "Listening for RTSP connection on " + iface
                    + " from Wifi display: " + mConnectedDevice.deviceName);

            mRemoteDisplay = RemoteDisplay.listen(iface, new RemoteDisplay.Listener() {
                @Override
                public void onDisplayConnected(final Surface surface,
                        final int width, final int height, final int flags) {
                    if (mConnectedDevice == oldDevice && !mRemoteDisplayConnected) {
                        Slog.i(TAG, "Opened RTSP connection with Wifi display: "
                                + mConnectedDevice.deviceName);
                        mRemoteDisplayConnected = true;
                        mHandler.removeCallbacks(mRtspTimeout);

                        final WifiDisplay display = createWifiDisplay(mConnectedDevice);
                        mHandler.post(new Runnable() {
                            @Override
                            public void run() {
                                mListener.onDisplayConnected(display,
                                        surface, width, height, flags);
                            }
                        });
                    }
                }

                @Override
                public void onDisplayDisconnected() {
                    if (mConnectedDevice == oldDevice) {
                        Slog.i(TAG, "Closed RTSP connection with Wifi display: "
                                + mConnectedDevice.deviceName);
                        mHandler.removeCallbacks(mRtspTimeout);
                        disconnect();
                    }
                }

                @Override
                public void onDisplayError(int error) {
                    if (mConnectedDevice == oldDevice) {
                        Slog.i(TAG, "Lost RTSP connection with Wifi display due to error "
                                + error + ": " + mConnectedDevice.deviceName);
                        mHandler.removeCallbacks(mRtspTimeout);
                        handleConnectionFailure(false);
                    }
                }
            }, mHandler);

            mHandler.postDelayed(mRtspTimeout, RTSP_TIMEOUT_SECONDS * 1000);
        }
    }

    private void setRemoteSubmixOn(boolean on) {
        if (mRemoteSubmixOn != on) {
            mRemoteSubmixOn = on;
            mAudioManager.setRemoteSubmixOn(on, REMOTE_SUBMIX_ADDRESS);
        }
    }

    private void handleStateChanged(boolean enabled) {
        if (mWifiP2pEnabled != enabled) {
            mWifiP2pEnabled = enabled;
            if (enabled) {
                if (!mWfdEnabled) {
                    enableWfd();
                }
            } else {
                setWfdEnabled(false);
                disconnect();
            }
        }
    }

    private void handlePeersChanged() {
        if (mWifiP2pEnabled) {
            if (mWfdEnabled) {
                requestPeers();
            } else {
                enableWfd();
            }
        }
    }

    private void handleConnectionChanged(NetworkInfo networkInfo) {
        mNetworkInfo = networkInfo;
        if (mWfdEnabled && networkInfo.isConnected()) {
            if (mDesiredDevice != null) {
                mWifiP2pManager.requestGroupInfo(mWifiP2pChannel, new GroupInfoListener() {
                    @Override
                    public void onGroupInfoAvailable(WifiP2pGroup info) {
                        if (DEBUG) {
                            Slog.d(TAG, "Received group info: " + describeWifiP2pGroup(info));
                        }

                        if (mConnectingDevice != null && !info.contains(mConnectingDevice)) {
                            Slog.i(TAG, "Aborting connection to Wifi display because "
                                    + "the current P2P group does not contain the device "
                                    + "we expected to find: " + mConnectingDevice.deviceName);
                            handleConnectionFailure(false);
                            return;
                        }

                        if (mDesiredDevice != null && !info.contains(mDesiredDevice)) {
                            disconnect();
                            return;
                        }

                        if (mConnectingDevice != null && mConnectingDevice == mDesiredDevice) {
                            Slog.i(TAG, "Connected to Wifi display: "
                                    + mConnectingDevice.deviceName);

                            mHandler.removeCallbacks(mConnectionTimeout);
                            mConnectedDeviceGroupInfo = info;
                            mConnectedDevice = mConnectingDevice;
                            mConnectingDevice = null;
                            updateConnection();
                        }
                    }
                });
            }
        } else {
            disconnect();

            // After disconnection for a group, for some reason we have a tendency
            // to get a peer change notification with an empty list of peers.
            // Perform a fresh scan.
            if (mWfdEnabled) {
                requestPeers();
            }
        }
    }

    private final Runnable mConnectionTimeout = new Runnable() {
        @Override
        public void run() {
            if (mConnectingDevice != null && mConnectingDevice == mDesiredDevice) {
                Slog.i(TAG, "Timed out waiting for Wifi display connection after "
                        + CONNECTION_TIMEOUT_SECONDS + " seconds: "
                        + mConnectingDevice.deviceName);
                handleConnectionFailure(true);
            }
        }
    };

    private final Runnable mRtspTimeout = new Runnable() {
        @Override
        public void run() {
            if (mConnectedDevice != null
                    && mRemoteDisplay != null && !mRemoteDisplayConnected) {
                Slog.i(TAG, "Timed out waiting for Wifi display RTSP connection after "
                        + RTSP_TIMEOUT_SECONDS + " seconds: "
                        + mConnectedDevice.deviceName);
                handleConnectionFailure(true);
            }
        }
    };

    private void handleConnectionFailure(boolean timeoutOccurred) {
        Slog.i(TAG, "Wifi display connection failed!");

        mHandler.post(new Runnable() {
            @Override
            public void run() {
                mListener.onDisplayConnectionFailed();
            }
        });

        if (mDesiredDevice != null) {
            if (mConnectionRetriesLeft > 0) {
                mHandler.postDelayed(new Runnable() {
                    @Override
                    public void run() {
                        retryConnection();
                    }
                }, timeoutOccurred ? 0 : CONNECT_RETRY_DELAY_MILLIS);
            } else {
                disconnect();
            }
        }
    }

    private static Inet4Address getInterfaceAddress(WifiP2pGroup info) {
        NetworkInterface iface;
        try {
            iface = NetworkInterface.getByName(info.getInterface());
        } catch (SocketException ex) {
            Slog.w(TAG, "Could not obtain address of network interface "
                    + info.getInterface(), ex);
            return null;
        }

        Enumeration<InetAddress> addrs = iface.getInetAddresses();
        while (addrs.hasMoreElements()) {
            InetAddress addr = addrs.nextElement();
            if (addr instanceof Inet4Address) {
                return (Inet4Address)addr;
            }
        }

        Slog.w(TAG, "Could not obtain address of network interface "
                + info.getInterface() + " because it had no IPv4 addresses.");
        return null;
    }

    private static int getPortNumber(WifiP2pDevice device) {
        if (device.deviceName.startsWith("DIRECT-")
                && device.deviceName.endsWith("Broadcom")) {
            // These dongles ignore the port we broadcast in our WFD IE.
            return 8554;
        }
        return DEFAULT_CONTROL_PORT;
    }

    private static boolean isWifiDisplay(WifiP2pDevice device) {
        return device.wfdInfo != null
                && device.wfdInfo.isWfdEnabled()
                && isPrimarySinkDeviceType(device.wfdInfo.getDeviceType());
    }

    private static boolean isPrimarySinkDeviceType(int deviceType) {
        return deviceType == WifiP2pWfdInfo.PRIMARY_SINK
                || deviceType == WifiP2pWfdInfo.SOURCE_OR_PRIMARY_SINK;
    }

    private static String describeWifiP2pDevice(WifiP2pDevice device) {
        return device != null ? device.toString().replace('\n', ',') : "null";
    }

    private static String describeWifiP2pGroup(WifiP2pGroup group) {
        return group != null ? group.toString().replace('\n', ',') : "null";
    }

    private static WifiDisplay createWifiDisplay(WifiP2pDevice device) {
        return new WifiDisplay(device.deviceAddress, device.deviceName);
    }

    private final BroadcastReceiver mWifiP2pReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            final String action = intent.getAction();
            if (action.equals(WifiP2pManager.WIFI_P2P_STATE_CHANGED_ACTION)) {
                boolean enabled = (intent.getIntExtra(WifiP2pManager.EXTRA_WIFI_STATE,
                        WifiP2pManager.WIFI_P2P_STATE_DISABLED)) ==
                        WifiP2pManager.WIFI_P2P_STATE_ENABLED;
                if (DEBUG) {
                    Slog.d(TAG, "Received WIFI_P2P_STATE_CHANGED_ACTION: enabled="
                            + enabled);
                }

                handleStateChanged(enabled);
            } else if (action.equals(WifiP2pManager.WIFI_P2P_PEERS_CHANGED_ACTION)) {
                if (DEBUG) {
                    Slog.d(TAG, "Received WIFI_P2P_PEERS_CHANGED_ACTION.");
                }

                handlePeersChanged();
            } else if (action.equals(WifiP2pManager.WIFI_P2P_CONNECTION_CHANGED_ACTION)) {
                NetworkInfo networkInfo = (NetworkInfo)intent.getParcelableExtra(
                        WifiP2pManager.EXTRA_NETWORK_INFO);
                if (DEBUG) {
                    Slog.d(TAG, "Received WIFI_P2P_CONNECTION_CHANGED_ACTION: networkInfo="
                            + networkInfo);
                }

                handleConnectionChanged(networkInfo);
            }
        }
    };

    /**
     * Called on the handler thread when displays are connected or disconnected.
     */
    public interface Listener {
        void onEnablementChanged(boolean enabled);

        void onScanStarted();
        void onScanFinished(WifiDisplay[] knownDisplays);

        void onDisplayConnecting(WifiDisplay display);
        void onDisplayConnectionFailed();
        void onDisplayConnected(WifiDisplay display,
                Surface surface, int width, int height, int flags);
        void onDisplayDisconnected();
    }
}