android udp发广播包,Android UDP 广播

2019-07-08 遇到的一点小问题

最近做局域网内Android端发UDP广播出去，然后接收服务器返回的信息。

参考的文章 Android UDP 广播实践，要用的都有写。

private final static String BROADCAST_IP = "255.255.255.255"; //广播范围

private final static int BROADCAST_PORT = 8888; //端口

DatagramSocket socket = new DatagramSocket(BROADCAST_PORT);

发送

byte[] sendBuf = 发送内容.getBytes();

InetAddress address = InetAddress.getByName(BROADCAST_IP);

DatagramPacket sendPacket = new DatagramPacket(sendBuf, sendBuf.length, address, BROADCAST_PORT);

socket.send(sendPacket);

socket.setBroadcast(true);

接收

byte[] ackBuf = new byte[1024];

InetAddress address = InetAddress.getByName(BROADCAST_IP);

DatagramPacket ackPacket = new DatagramPacket(ackBuf, ackBuf.length, address, BROADCAST_PORT);

socket.receive(ackPacket);

接收内容 = new String(ackPacket.getData(), 0, ackPacket.getLength());

应答的IP = ackPacket.getAddress().getHostAddress();

能收到udp消息，但有可能出现不在同一个广播地址，无法http沟通的情况，所以顺便查了下当前设备的广播地址，和服务器的比对。

/**

* 获取当前移动设备的广播地址

* 返回示例：192.168.11.255

*/

private String getPhoneBroadcast() throws SocketException {

System.setProperty("java.net.preferIPv4Stack", "true");

for (Enumeration niEnum = NetworkInterface.getNetworkInterfaces(); niEnum.hasMoreElements(); ) {

NetworkInterface ni = niEnum.nextElement();

if (!ni.isLoopback()) {

for (InterfaceAddress interfaceAddress : ni.getInterfaceAddresses()) {

if (interfaceAddress.getBroadcast() != null) {

return interfaceAddress.getBroadcast().toString().substring(1);

}

}

}

}

return null;

}