19

I am trying to develop an app that sends some broadcast messages and receives some answers from the other android devices. I am having some trouble receiving the UDP messages from the other devices. I should mention that this code worked on Gingerbread but on JellyBean it's not working anymore and I do not know what might be the problem.

Here is where I send the broadcast message (I know the other devices listen on port 5000) : 

 private void sendUDPMessage(String msg) {

    try {
        DatagramSocket clientSocket = new DatagramSocket();

        clientSocket.setBroadcast(true);
        InetAddress address = InetAddress.getByName(Utils.getBroadcastAddress());

        byte[] sendData;

        sendData = msg.getBytes();
        DatagramPacket sendPacket = new DatagramPacket(sendData,
                sendData.length, address, 5000);
        clientSocket.send(sendPacket);

        clientSocket.close();
    } catch (Exception e) {
        e.printStackTrace();
    }

}

And here is where I receive it :

private void start_UDP()
{
    try {
            serverSocketUDP = new DatagramSocket(5000);
        }
    catch (Exception e) {

        Log.i(LOGTAG, "Exception opening DatagramSocket UDP");
    }

    final byte[] receiveData = new byte[1024];


    while(runningUDP) {
        Log.d(LOGTAG, "Waiting for Broadcast request in ServerUDP.");

        final DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);

        serverSocketUDP.receive(receivePacket);


                byte[] sendData = new byte[1024];
                InetAddress address = receivePacket.getAddress();
                int port = receivePacket.getPort();
                if(!receivePacket.getAddress().getHostAddress().equals(Utils.getLocalIpAddress()))
                {
                    String req = new String(receivePacket.getData(), 0, receivePacket.getLength());


                    Log.d(LOGTAG, "Received UDP message : "+req+" from: "+receivePacket.getAddress().getHostAddress());
                }
                      }// while ends
       }//method ends

I should mention that these 2 functions are separate in 2 different threads so I can send and receive simultaneously.

I also acquire the following locks:

    powerManager =(PowerManager)context.getSystemService(Context.POWER_SERVICE);
    wakeLock = powerManager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK ,LOGTAG); // PARTIAL_WAKE_LOCK Only keeps CPU on
    wifiManager = (WifiManager)context.getSystemService(Context.WIFI_SERVICE);
    wifiLock = wifiManager.createWifiLock(3, LOGTAG);
    multicastLock = wifiManager.createMulticastLock(LOGTAG);

    wakeLock.acquire();
    multicastLock.acquire();
    wifiLock.acquire();

And the permissions on the Manifest file : 

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
<uses-permission android:name="android.permission.WAKE_LOCK" />
<uses-permission android:name="android.permission.WRITE_SETTINGS"/>
<uses-permission android:name="android.permission.CHANGE_WIFI_MULTICAST_STATE"/>

I have tested if the messages are sent using wireshark and tcpdump and they are sent. Moreover, what is even more strange, I receive the broadcast messages that I send (but I discard them because I dont need to process the messages sent from myself) but I dont receive the broadcast messages sent from the other devices (which should have the same format, only the source address would be different and the message contained, either way should not affect the broadcast message).

Please let me know if you have any ideas because I really ran out of anything else I could try. Any help would be appreciated. Thanks!

EDIT: I have made some tests and even if when I run on each of the phones ifconfig wlan0 and it says something like 

  ifconfig wlan0
  wlan0: ip 169.254.17.28 mask 255.255.0.0 flags [up broadcast multicast]

which means that the interface is active and the IP is set and can receive broadcast messages and multicast msgs but when I use

                 InetAddress in=InetAddress.getByName("169.254.17.28");
            if (in.isReachable(1000))
                Log.i(LOGTAG, "host is reachable");
            else
                Log.i(LOGTAG, "host is not reachable");

It shows in the logs host is not reachable.

This is where I turn on the Wi-fi 

    private void startWifiAdhoc() {

    WifiManager wifiManager =     (WifiManager)SharingFileService.context.getSystemService(Context.WIFI_SERVICE);
    String command="";
    if (condWifiAdhoc == false) {

        condWifiAdhoc=true;
        wifiInterface = Utils.getWifiInterface();


        wifiManager.setWifiEnabled(true);
        localIP = Utils.getLinkLocalAddress();
    }
    else
    {
        wifiManager.setWifiEnabled(true);
        localIP = Utils.getLinkLocalAddress();
    }
        // Set wifi ad-hoc
        command = context.getFilesDir().getPath()
                + "/iwconfig " + wifiInterface + " mode ad-hoc essid "
                + "mcp" + " channel " + "1" + " commit\n";

        Log.i(LOGTAG, command);
        Utils.rootExec(command);


        Log.i(LOGTAG, "Ip address used :" + localIP);
        command = context.getFilesDir().getPath()
                + "/ifconfig " + wifiInterface + " " + localIP
                + " netmask 255.255.0.0 up\n";



        Log.i(LOGTAG, command);
        Utils.rootExec(command);

}
4

2 回答 2

27

我通过使用此处描述的方法来计算广播地址来完成这项工作：https ://code.google.com/p/boxeeeremote/wiki/AndroidUDP

这是我的接收器：

try {
  //Keep a socket open to listen to all the UDP trafic that is destined for this port
  socket = new DatagramSocket(Constants.PORT, InetAddress.getByName("0.0.0.0"));
  socket.setBroadcast(true);

  while (true) {
    Log.i(TAG,"Ready to receive broadcast packets!");

    //Receive a packet
    byte[] recvBuf = new byte[15000];
    DatagramPacket packet = new DatagramPacket(recvBuf, recvBuf.length);
    socket.receive(packet);

    //Packet received
    Log.i(TAG, "Packet received from: " + packet.getAddress().getHostAddress());
    String data = new String(packet.getData()).trim();
    Log.i(TAG, "Packet received; data: " + data);

    // Send the packet data back to the UI thread
    Intent localIntent = new Intent(Constants.BROADCAST_ACTION)
            // Puts the data into the Intent
            .putExtra(Constants.EXTENDED_DATA_STATUS, data);
    // Broadcasts the Intent to receivers in this app.
    LocalBroadcastManager.getInstance(this).sendBroadcast(localIntent);
  }
} catch (IOException ex) {
  Log.i(TAG, "Oops" + ex.getMessage());
}

这是我的发件人：

    public void sendBroadcast(String messageStr) {
    // Hack Prevent crash (sending should be done using an async task)
    StrictMode.ThreadPolicy policy = new   StrictMode.ThreadPolicy.Builder().permitAll().build();
    StrictMode.setThreadPolicy(policy);

    try {
      //Open a random port to send the package
      DatagramSocket socket = new DatagramSocket();
      socket.setBroadcast(true);
      byte[] sendData = messageStr.getBytes();
      DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, getBroadcastAddress(), Constants.PORT);
      socket.send(sendPacket);
      System.out.println(getClass().getName() + "Broadcast packet sent to: " + getBroadcastAddress().getHostAddress());
    } catch (IOException e) {
      Log.e(TAG, "IOException: " + e.getMessage());
    }
  }

  InetAddress getBroadcastAddress() throws IOException {
    WifiManager wifi = (WifiManager) mContext.getSystemService(Context.WIFI_SERVICE);
    DhcpInfo dhcp = wifi.getDhcpInfo();
    // handle null somehow

    int broadcast = (dhcp.ipAddress & dhcp.netmask) | ~dhcp.netmask;
    byte[] quads = new byte[4];
    for (int k = 0; k < 4; k++)
      quads[k] = (byte) ((broadcast >> k * 8) & 0xFF);
    return InetAddress.getByAddress(quads);
  }
于 2014-08-27T06:26:41.623 回答
3

我在尝试解决类似问题时遇到了您的帖子。你让你的东西工作了吗？

就我而言，我一直试图让 Nexus 7（第一代使用 Jelly Bean 4.3）和 Nexus One（Gingerbread 2.3.6）通过 UDP 相互通信。最初，我的应用程序在两台设备上运行，可以成功连接，但只能通过从手机到平板电脑的单向通信。我在清单中只有一个权限：INTERNET。一旦我将 ACCESS_NETWORK_STATE 权限添加到清单中，从平板电脑到手机的通信就开始工作了。

因此，出于某种原因，Nexus 7 只对发送和接收 UDP 数据包的 INTERNET 权限感到满意（嗯，至少是我的特定实现）。Nexus One 将仅使用 INTERNET 权限发送，但不会接收，除非也给予 ACCESS_NETWORK_STATE 权限。

您的代码看起来与我的相似（但是，我不认识您的“UTILS.”调用）。不过，就我而言，出于测试目的，我对广播地址 (192.168.n.255) 进行了硬编码。我在接入点上，而您在 adhoc 网络上。也许这也有一些影响。

于 2013-08-08T16:51:14.810 回答