Android UDP简单实现

说明

测试程序分为两个部分：Android客户端、Java服务端。

Android客户端：向局域网UDP广播字符串“Hello, World!”，端口号是11000。然后打印所有收到的UDP广播。

Java服务端：监听11000的UDP广播，收到UDP广播后，发送一个JSON串。

Android客户端

[code]public class MainActivity extends Activity {

    // UDP广播IP和PORT
    public static final String SERVERIP = "255.255.255.255";
    public static final int SERVERPORT = 11000;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        new Thread(new Client()).start();
    }

    DatagramSocket socket = null;

    public class Client implements Runnable {

        public void run() {

            // 向局域网UDP广播信息：Hello, World!
            try {

                InetAddress serverAddress = InetAddress.getByName(SERVERIP);
                System.out.println("Client: Start connecting\n");
                socket = new DatagramSocket(SERVERPORT);
                byte[] buf = "Hello, World!".getBytes();

                DatagramPacket packet = new DatagramPacket(buf, buf.length,
                        serverAddress, SERVERPORT);
                System.out.println("Client: Sending ‘" + new String(buf)
                        + "’\n");
                socket.send(packet);

                System.out.println("Client: Message sent\n");
                System.out.println("Client: Succeed!\n");

            } catch (UnknownHostException e) {
                e.printStackTrace();
            } catch (SocketException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }

            // 接收UDP广播，有的手机不支持
            while (true) {
                byte[] recbuf = new byte[255];
                DatagramPacket recpacket = new DatagramPacket(recbuf,
                        recbuf.length);

                try {
                    socket.receive(recpacket);
                } catch (IOException e) {
                    e.printStackTrace();
                }

                System.out.println("Server: Message received: ‘"
                        + new String(recpacket.getData()) + "’\n");
                System.out.println("Server: IP " + recpacket.getAddress()
                        + "’\n");
            }
        }
    }

}

AndroidManifest中添加Internet权限

[code]<uses-permission android:name="android.permission.INTERNET" />

Java服务端

[code]class UDPServer {

    public static void main(String[] args) throws IOException {

        DatagramSocket server = new DatagramSocket(11000);

        while (true) {

            byte[] recvBuf = new byte[100];
            DatagramPacket recvPacket = new DatagramPacket(recvBuf,
                    recvBuf.length);

            server.receive(recvPacket);

            String recvStr = new String(recvPacket.getData(), 0,
                    recvPacket.getLength());

            System.out.println();
            System.out.println("收到的内容：" + recvStr);
            System.out.println("收到的ip：" + recvPacket.getAddress());

            // 发送UDP消息，JSON格式数据
            // {"name":"123","ID":"Robot007","BATTERY":"2.7f"}

            int port = recvPacket.getPort();
            InetAddress addr = recvPacket.getAddress();

            JSONObject json = new JSONObject();

            json.put("name", "Computer7");
            json.put("ID", "Robot007");
            json.put("BATTERY", "2.7f");

            byte[] sendBuf = json.toString().getBytes();
            DatagramPacket sendPacket = new DatagramPacket(sendBuf,
                    sendBuf.length, addr, port);

            server.send(sendPacket);
        }
    }
}