【发布时间】：2015-08-05 16:18:38
【问题描述】：
我的 Android 应用需要知道在我的本地网络上运行服务器的机器的 ip。我的计划是在我的应用程序中广播一个 UDP 数据包并从服务器发回一个数据包，以便应用程序知道 IP。
这是我在 Android 上的代码：
...
new SendUDPTask().execute();
...
/************ getBroadcastAddress: know where to send the signal to find the server ***********/
private InetAddress getBroadcastAddress() {
//setup
WifiManager wifiManager = (WifiManager) getSystemService(Context.WIFI_SERVICE);
DhcpInfo dhcp = wifiManager.getDhcpInfo();
//complicated stuff
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 result
InetAddress result = null;
try {
result = InetAddress.getByAddress(quads);
} catch (UnknownHostException e) {
e.printStackTrace();
}
return result;
}
/************ sendUDP: here e send the packet that will allow us to find the server ***********/
private DatagramPacket sendUDP(String req, int port) throws IOException {
DatagramSocket socket = new DatagramSocket(port);
socket.setBroadcast(true);
InetAddress broadcastAddress = getBroadcastAddress();
DatagramPacket packet = new DatagramPacket(req.getBytes(), req.length(), broadcastAddress, port);
socket.send(packet);
byte[] buf = new byte[1024];
packet = new DatagramPacket(buf, buf.length);
socket.setSoTimeout(3000);
//We wouldn't want to think our own message is the server's response
String myAddress = getMyAddress();
socket.receive(packet);
while (packet.getAddress().getHostAddress().contains(
myAddress))
{
socket.receive(packet);
}
socket.close();
return packet;
}
/***************************** getMyAddress: the device's address *****************************/
public String getMyAddress() {
try {
for (Enumeration<NetworkInterface> en = NetworkInterface.getNetworkInterfaces(); en.hasMoreElements();) {
NetworkInterface intf = en.nextElement();
for (Enumeration<InetAddress> enumIpAddr = intf.getInetAddresses(); enumIpAddr.hasMoreElements();) {
InetAddress inetAddress = enumIpAddr.nextElement();
if (!inetAddress.isLoopbackAddress())
return inetAddress.getHostAddress();
}
}
}
catch (SocketException e) {
e.printStackTrace();
}
return null;
}
private class SendUDPTask extends AsyncTask<String, Void, DatagramPacket> {
private Exception exception;
protected DatagramPacket doInBackground(String... params) {
try {
DatagramPacket packet = sendUDP("Ping", 31415);
Log.d("GJ", packet.getAddress().getHostAddress().toString());
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
protected void onPostExecute(DatagramPacket packet) {
}
}
这是我电脑上的代码（Node.js）：
var PORT = 31415;
var HOST = '127.0.0.1';
var dgram = require('dgram');
var server = dgram.createSocket('udp4');
server.on('listening', function () {
var address = server.address();
console.log('UDP Server listening on ' + address.address + ':' + address.port);
});
server.on('message', function (message, remote) {
console.log(remote.address + ':' + remote.port + ' - ' + message);
});
server.bind(PORT, HOST);
我还没有发回任何东西，但我应该看到console.log。我没有看到任何东西，这一定意味着数据包没有到达。
有人有想法吗？
非常感谢
【问题讨论】：
标签： android node.js sockets networking