Java 通过Wi-Fi直接广播

我正在考虑在多个Android设备之间通过Wi-Fi直接连接进行广播的可能性。我已经创建了一个简单的消息广播应用程序来测试它是否工作，但到目前为止我还不能广播消息。当我尝试发送数据包时，我收到一个SocketException（无法访问网络）：

这是我的代码的精髓：

InetAddress broadcastAddress = InetAddress.getByName("255.255.255.255");
int port = 8888;

DatagramSocket socket = new DatagramSocket(port);
socket.setBroadcast(true);
socket.connect(broadcastAddress, port);

String message = "Hello";
byte[] buffer = message.getBytes();

DatagramPacket packet = new DatagramPacket(
        buffer, buffer.length, broadcastAddress, port);

try {
    socket.send(packet); // <----- Causes a SocketException
} catch (IOException e) {
    Log.e(TAG, e.getMessage(), e);
}

我还尝试将

InetAddress.getByName（“0.0.0.0”）

作为参数添加到

DatagramSocket

，但没有成功

---

建议？

无耻地从

尝试通过以下方式获得网络连接：

InetAddress getBroadcastAddress() throws IOException {
    WifiManager wifi = 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);
}  

编辑：从同一页阅读尝试此

WifiManager wifi = (WifiManager) this.getSystemService(Context.WIFI_SERVICE);
MulticastLock lock = wifi.createMulticastLock("dk.aboaya.pingpong");
lock.acquire();
serverSocket = new DatagramSocket(19876);
serverSocket.setSoTimeout(15000); //15 sec wait for the client to connect
byte[] data = new byte[UDPBatPositionUpdater.secretWord.length()]; 
DatagramPacket packet = new DatagramPacket(data, data.length);
serverSocket.receive(packet);
lock.release();
String s = new String(packet.getData());
System.out.println(s);

请记住，要使其工作，您需要以下权限：

---

使用该功能获取广播地址后，SocketException消失，广播似乎正常，但我在第二台设备上接收广播时遇到问题。我在接收设备上以相同的方式初始化一个

DatagramSocket

。我还尝试通过添加

InetAddress.getByName（“0.0.0.0”）

作为参数，在接收

DatagramSocket

上使用通配符地址。不走运。@user2190832在我的答案中添加了更多细节来阅读UDP。代码非常有用，谢谢！关于设备的一些细节：我构建了自己的库来处理基于此代码的通信。我目前正在使用8888端口。我的Nexus 5可以发送和接收。My Moto G只能发送软件包（并接收自己的软件包，但不能从其他设备接收）。我最近尝试了三星Galaxy S2，可以收发软件包。莫名其妙的是，摩托罗拉正在屏蔽接收到的广播。我尝试了两种不同的Moto G，一种是使用了特定的防火墙策略，另一种是库存，但没有成功。顺便说一句：看看这篇文章：

InetAddress getBroadcastAddress() throws IOException {
    WifiManager wifi = 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);
}  

DatagramSocket socket = new DatagramSocket(PORT);
socket.setBroadcast(true);
DatagramPacket packet = new DatagramPacket(data.getBytes(), data.length(),
    getBroadcastAddress(), PORT);
socket.send(packet);

// If you want to listen for a response ...
byte[] buf = new byte[1024];
DatagramPacket packet = new DatagramPacket(buf, buf.length);
socket.receive(packet);

WifiManager wifi = (WifiManager) this.getSystemService(Context.WIFI_SERVICE);
MulticastLock lock = wifi.createMulticastLock("dk.aboaya.pingpong");
lock.acquire();
serverSocket = new DatagramSocket(19876);
serverSocket.setSoTimeout(15000); //15 sec wait for the client to connect
byte[] data = new byte[UDPBatPositionUpdater.secretWord.length()]; 
DatagramPacket packet = new DatagramPacket(data, data.length);
serverSocket.receive(packet);
lock.release();
String s = new String(packet.getData());
System.out.println(s);