Question

我正在尝试开发一个发送一些广播消息的应用程序，并从其他Android设备接收一些答案。我在从其他设备接收UDP消息时遇到一些麻烦。我应该提一下，这个代码适用于Gingerbread，但是在JellyBean上它已经不能用了，我不知道可能是什么问题。

这是我发送广播消息的地方（我知道其他设备在端口5000上侦听）：

 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();
    }

}

这是我收到它的地方：

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

我应该提到这两个函数在2个不同的线程中是分开的，所以我可以同时发送和接收。

我还获得了以下锁：

    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();

Manifest文件的权限：

<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"/>

我已经测试过是否使用wireshark和tcpdump发送消息并发送它们。而且，更奇怪的是，我接收到我发送的广播消息（但我丢弃它们因为我不需要处理自己发送的消息）但是我没有收到从其他设备发送的广播消息（应该有相同的格式，只有源地址不同，所包含的消息，无论哪种方式都不应影响广播消息）。

如果您有任何想法，请告诉我，因为我真的用完了其他任何我可以尝试的东西。任何帮助，将不胜感激。谢谢！

编辑：我已经做了一些测试，即使我在每个手机上运行ifconfig wlan0并且它表示类似

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

表示接口处于活动状态且IP已设置，可以接收广播消息和组播消息但是当我使用时

                 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");

它显示在日志主机中无法访问。

这是我打开Wi-Fi的地方

    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);

}

Answer 1

我通过使用此处描述的方法来计算广播地址：https://code.google.com/p/boxeeremote/wiki/AndroidUDP

这是我的接收者：

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);
  }

Answer 2

我在尝试解决类似问题时遇到了您的帖子。你有没有让你的东西工作？

在我的情况下，我一直试图通过UDP与Nexus 7（Jelly Bean 4.3的第一代）和Nexus One（Gingerbread 2.3.6）相互交谈。最初，我的应用程序在两台设备上运行，都可以成功连接，但只能通过手机与平板电脑进行单向通信。我在清单中只有一个许可：互联网。在向清单添加ACCESS_NETWORK_STATE权限后，从平板电脑到手机的通信开始工作。

因此，出于某种原因，Nexus 7对发送和接收UDP数据包的INTERNET权限感到满意（至少，我的特定实现）。 Nexus One将仅使用INTERNET权限发送，但除非同时授予ACCESS_NETWORK_STATE权限，否则不会收到。

您的代码与我的代码类似（但我不认识您的“UTILS。”调用）。但就我而言，为了测试的目的，我对广播地址进行了硬编码（192.168.n.255）。当你在一个adhoc网络上时，我正在接入点。也许这也有一些影响。

发送广播UDP但不在其他Android设备上接收

2 个答案: