我正在尝试开发一个发送一些广播消息并从其他android设备接收一些答案的应用程序。我在从其他设备接收UDP消息时遇到了一些麻烦。我应该提到的是,此代码可在Gingerbread上使用,但在JellyBean上将无法使用,并且我不知道这可能是问题所在。
这是我发送广播消息的位置(我知道其他设备在端口5000上监听):
private void sendUDPMessage(String msg) {
try {
DatagramSocket clientSocket = new DatagramSocket();
clientSocket.setBroadcast(true);
InetAddress address = InetAddress.getByName(Utils.getBroadcastAddress());
byte[] sendData;
sendData = msg.getBytes();
DatagramPacket sendPacket = new DatagramPacket(sendData,
sendData.length, address, 5000);
clientSocket.send(sendPacket);
clientSocket.close();
} catch (Exception e) {
e.printStackTrace();
}
}
这是我收到的地方:
private void start_UDP()
{
try {
serverSocketUDP = new DatagramSocket(5000);
}
catch (Exception e) {
Log.i(LOGTAG, "Exception opening DatagramSocket UDP");
}
final byte[] receiveData = new byte[1024];
while(runningUDP) {
Log.d(LOGTAG, "Waiting for Broadcast request in ServerUDP.");
final DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
serverSocketUDP.receive(receivePacket);
byte[] sendData = new byte[1024];
InetAddress address = receivePacket.getAddress();
int port = receivePacket.getPort();
if(!receivePacket.getAddress().getHostAddress().equals(Utils.getLocalIpAddress()))
{
String req = new String(receivePacket.getData(), 0, receivePacket.getLength());
Log.d(LOGTAG, "Received UDP message : "+req+" from: "+receivePacket.getAddress().getHostAddress());
}
}// while ends
}//method ends
我应该提到,这2个函数分别位于2个不同的线程中,因此我可以同时发送和接收。
我还获得了以下锁:
powerManager =(PowerManager)context.getSystemService(Context.POWER_SERVICE);
wakeLock = powerManager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK ,LOGTAG); // PARTIAL_WAKE_LOCK Only keeps CPU on
wifiManager = (WifiManager)context.getSystemService(Context.WIFI_SERVICE);
wifiLock = wifiManager.createWifiLock(3, LOGTAG);
multicastLock = wifiManager.createMulticastLock(LOGTAG);
wakeLock.acquire();
multicastLock.acquire();
wifiLock.acquire();
以及对 list 文件的权限:
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
<uses-permission android:name="android.permission.WAKE_LOCK" />
<uses-permission android:name="android.permission.WRITE_SETTINGS"/>
<uses-permission android:name="android.permission.CHANGE_WIFI_MULTICAST_STATE"/>
我已经测试了消息是否使用wireshark和tcpdump发送,并且它们是否已发送。而且,更奇怪的是,我收到了发送的广播消息(但是我丢弃了它们,因为我不需要处理自己发送的消息),但是却没有收到从其他设备发送的广播消息(应该具有格式相同,只是源地址和所包含的消息不同,无论哪种方式都不会影响广播消息)。
如果您有任何想法,请告诉我,因为我真的没有其他可以尝试的东西。任何帮助,将不胜感激。谢谢!
编辑:
我进行了一些测试,即使在每部手机上运行时,ifconfig wlan0都显示类似
ifconfig wlan0
wlan0: ip 169.254.17.28 mask 255.255.0.0 flags [up broadcast multicast]
这意味着该接口(interface)处于 Activity 状态并且已设置IP,并且可以接收广播消息和多播msg,但是当我使用
InetAddress in=InetAddress.getByName("169.254.17.28");
if (in.isReachable(1000))
Log.i(LOGTAG, "host is reachable");
else
Log.i(LOGTAG, "host is not reachable");
它显示在日志主机中无法访问。
这是我打开Wi-fi的地方
private void startWifiAdhoc() {
WifiManager wifiManager = (WifiManager)SharingFileService.context.getSystemService(Context.WIFI_SERVICE);
String command="";
if (condWifiAdhoc == false) {
condWifiAdhoc=true;
wifiInterface = Utils.getWifiInterface();
wifiManager.setWifiEnabled(true);
localIP = Utils.getLinkLocalAddress();
}
else
{
wifiManager.setWifiEnabled(true);
localIP = Utils.getLinkLocalAddress();
}
// Set wifi ad-hoc
command = context.getFilesDir().getPath()
+ "/iwconfig " + wifiInterface + " mode ad-hoc essid "
+ "mcp" + " channel " + "1" + " commit\n";
Log.i(LOGTAG, command);
Utils.rootExec(command);
Log.i(LOGTAG, "Ip address used :" + localIP);
command = context.getFilesDir().getPath()
+ "/ifconfig " + wifiInterface + " " + localIP
+ " netmask 255.255.0.0 up\n";
Log.i(LOGTAG, command);
Utils.rootExec(command);
}
最佳答案
我通过使用此处描述的方法来计算广播地址来完成此工作:https://code.google.com/p/boxeeremote/wiki/AndroidUDP
这是我的接收者:
try {
//Keep a socket open to listen to all the UDP trafic that is destined for this port
socket = new DatagramSocket(Constants.PORT, InetAddress.getByName("0.0.0.0"));
socket.setBroadcast(true);
while (true) {
Log.i(TAG,"Ready to receive broadcast packets!");
//Receive a packet
byte[] recvBuf = new byte[15000];
DatagramPacket packet = new DatagramPacket(recvBuf, recvBuf.length);
socket.receive(packet);
//Packet received
Log.i(TAG, "Packet received from: " + packet.getAddress().getHostAddress());
String data = new String(packet.getData()).trim();
Log.i(TAG, "Packet received; data: " + data);
// Send the packet data back to the UI thread
Intent localIntent = new Intent(Constants.BROADCAST_ACTION)
// Puts the data into the Intent
.putExtra(Constants.EXTENDED_DATA_STATUS, data);
// Broadcasts the Intent to receivers in this app.
LocalBroadcastManager.getInstance(this).sendBroadcast(localIntent);
}
} catch (IOException ex) {
Log.i(TAG, "Oops" + ex.getMessage());
}
这是我的发件人:
public void sendBroadcast(String messageStr) {
// Hack Prevent crash (sending should be done using an async task)
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
try {
//Open a random port to send the package
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();
// 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);
}