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simplify mdns query and use MulticastSocket to set TTL to 1

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This commit is contained in:
Anton Keks 2014-09-30 00:15:40 +03:00
parent 75e204e29b
commit c583e79fc2
1 changed files with 12 additions and 5 deletions
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17
src/net/azib/ipscan/util/MDNSResolver.java
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@ -5,16 +5,19 @@ import java.io.Closeable;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.MulticastSocket;
public class MDNSResolver implements Closeable {
DatagramSocket socket = new DatagramSocket();
InetAddress mdnsIP = InetAddress.getByName("224.0.0.251");
private int mdnsPort = 5353;
MulticastSocket socket = new MulticastSocket();
public MDNSResolver(int timeout) throws IOException {
socket.setSoTimeout(timeout);
socket.setTimeToLive(1);
// TODO: iPhones respond only back to the multicast address and port 5353 provided requestId == 0
// socket.joinGroup(mdnsIP);
}
void writeName(DataOutputStream out, String name) throws IOException {
@ -45,10 +48,9 @@ public class MDNSResolver implements Closeable {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
DataOutputStream out = new DataOutputStream(baos);
out.writeShort(id);
out.write(new byte[] {1, 0x20, 0, 1, 0, 0, 0, 0, 0, 1});
out.write(new byte[] {0, 0, 0, 1, 0, 0, 0, 0, 0, 0});
writeName(out, name);
out.write(new byte[] {0, 0xc, 0, 1});
out.write(new byte[] {0, 0, 0x29, 0x10, 0, 0, 0, 0, 0, 0, 0});
return baos.toByteArray();
}
@ -67,11 +69,16 @@ public class MDNSResolver implements Closeable {
socket.receive(respPacket);
byte[] response = respPacket.getData();
if (response[0] != request[0] && response[1] != request[1]) return null;
int offset = request.length + 1;
int numQueries = response[5];
int offset = (numQueries == 0 ? 12 : request.length) + 2 + 2 + 2 + 4 + 2;
return decodeName(response, offset, respPacket.getLength() - offset);
}
public void close() {
socket.close();
}
public static void main(String[] args) throws IOException {
System.out.println(new MDNSResolver(2000).resolve(InetAddress.getByName("192.168.0.10")));
}
}