如何从 Android 广播 UDP 数据包？

Question

我需要使用 UDP 从我的 Android 应用程序向我的网络（以太网）上的每台设备广播一条消息。 我不知道如何做到这一点，因为似乎没有任何关于如何发送广播消息的文档，只有关于如何使用 IP 地址发送到特定客户端的文档。

谢谢

Answer 1

这是一个有用的文档：

google-AdroidUDP

这是一个示例代码：

1- 发件人

 public void sendBroadcast(String messageStr) {
 StrictMode.ThreadPolicy policy = new   StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);

try {

  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();


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);

}

2- 接收者：

      try {
      socket = new DatagramSocket(Constants.PORT, InetAddress.getByName("0.0.0.0"));
 socket.setBroadcast(true);

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

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

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

Intent localIntent = new Intent(Constants.BROADCAST_ACTION)
        .putExtra(Constants.EXTENDED_DATA_STATUS, data);
LocalBroadcastManager.getInstance(this).sendBroadcast(localIntent);
    }
    }  catch (IOException ex) {
    Log.i(TAG, "Oops" + ex.getMessage());
    }