我正在寻找在多个Android设备之间通过Wi-Fi Direct连接进行广播的可能性。我创建了一个简单的消息广播应用程序,以测试它是否有效,但是到目前为止,我还无法广播消息。当我尝试发送数据包时,我收到 SocketException (网络无法访问):
03-20 13:23:00.148: E/UdpBroadcaster(4180): sendto failed: ENETUNREACH (Network is unreachable)
03-20 13:23:00.148: E/UdpBroadcaster(4180): java.net.SocketException: sendto failed: ENETUNREACH (Network is unreachable)
03-20 13:23:00.148: E/UdpBroadcaster(4180): at libcore.io.IoBridge.maybeThrowAfterSendto(IoBridge.java:496)
03-20 13:23:00.148: E/UdpBroadcaster(4180): at libcore.io.IoBridge.sendto(IoBridge.java:465)
03-20 13:23:00.148: E/UdpBroadcaster(4180): at java.net.PlainDatagramSocketImpl.send(PlainDatagramSocketImpl.java:182)
03-20 13:23:00.148: E/UdpBroadcaster(4180): at java.net.DatagramSocket.send(DatagramSocket.java:307)
03-20 13:23:00.148: E/UdpBroadcaster(4180): at com.example.android.wifidirect.UdpBroadcaster.sendMessage(UdpBroadcaster.java:59)
03-20 13:23:00.148: E/UdpBroadcaster(4180): at com.example.android.wifidirect.UdpBroadcaster.run(UdpBroadcaster.java:44)
03-20 13:23:00.148: E/UdpBroadcaster(4180): Caused by: libcore.io.ErrnoException: sendto failed: ENETUNREACH (Network is unreachable)
03-20 13:23:00.148: E/UdpBroadcaster(4180): at libcore.io.Posix.sendtoBytes(Native Method)
03-20 13:23:00.148: E/UdpBroadcaster(4180): at libcore.io.Posix.sendto(Posix.java:146)
03-20 13:23:00.148: E/UdpBroadcaster(4180): at libcore.io.BlockGuardOs.sendto(BlockGuardOs.java:177)
03-20 13:23:00.148: E/UdpBroadcaster(4180): at libcore.io.IoBridge.sendto(IoBridge.java:463)
03-20 13:23:00.148: E/UdpBroadcaster(4180): ... 4 more
这是我的代码的本质:
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);
}
This post建议应该可以通过Wi-Fi Direct进行广播。
有谁知道在 Android 设备上通过Wi-Fi Direct广播是否真的有效?如果它可以正常工作,我在做什么错?
我开始认为设备不知道将广播数据包路由到何处。在我的情况下,它需要工作而不必生根设备并手动为广播数据包添加路由。
更新
使用Romain Hippeau建议的
getBroadcastAddress()
函数后,SocketException消失了,广播似乎按预期工作了。但是,我在第二台设备上接收广播时遇到问题。我正在使用以下代码来接收广播:
DatagramSocket socket = null;
try {
socket = new DatagramSocket(8888);
socket.setBroadcast(true); // Not needed?
socket.setSoTimeout(200);
DatagramPacket packet = null;
while (!mStopping) {
byte[] buffer = new byte[1024];
packet = new DatagramPacket(buffer, buffer.length);
try {
socket.receive(packet);
if (packet.getData().length > 0) {
String receivedString = new String(packet.getData());
Log.i(TAG, "Received string: " + receivedString);
}
} catch (InterruptedIOException e) { /* Ignore */ }
}
} catch (IOException e) {
Log.e(TAG, e.getMessage(), e);
} finally {
if (socket != null)
socket.close();
}
我还尝试通过将
DatagramSocket
添加为参数来向InetAddress.getByName("0.0.0.0")
添加通配符地址,但是没有运气。有什么建议吗?
最佳答案
从https://code.google.com/p/boxeeremote/wiki/AndroidUDP 无耻地被盗
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);
}
然后尝试以这种方式发送数据包:
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);
编辑:从同一页上阅读尝试此...
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,您需要具有以下权限才能运行: