├── README
├── .gitignore
├── mdns-core
    ├── src
    │   └── main
    │   │   └── java
    │   │       └── net
    │   │           └── cheney
    │   │               └── mdns
    │   │                   ├── DNSMessage.java
    │   │                   ├── CachedRecord.java
    │   │                   ├── DNSQuery.java
    │   │                   ├── MdnsListener.java
    │   │                   ├── DNSRequestBuilder.java
    │   │                   ├── Record.java
    │   │                   ├── DNSResponseParser.java
    │   │                   └── DNSResponse.java
    └── pom.xml
└── pom.xml


/README:
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1 | 


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/.gitignore:
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1 | .classpath
2 | .project
3 | .settings/
4 | target/
5 | bin/
6 | 


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/mdns-core/src/main/java/net/cheney/mdns/DNSMessage.java:
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1 | package net.cheney.mdns;
2 | 
3 | public abstract class DNSMessage {
4 | 
5 | }
6 | 


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/mdns-core/src/main/java/net/cheney/mdns/CachedRecord.java:
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 1 | package net.cheney.mdns;
 2 | 
 3 | public class CachedRecord extends Record {
 4 | 
 5 | 	public CachedRecord(Type type, Class recordClass, String name, int ttl) {
 6 | 		super(type, recordClass, name, ttl);
 7 | 	}
 8 | 
 9 | }
10 | 


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/mdns-core/pom.xml:
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 1 | <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 2 | 	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
 3 | 	<parent>
 4 | 		<artifactId>mdns</artifactId>
 5 | 		<groupId>net.cheney.mdns</groupId>
 6 | 		<version>0.0.1-SNAPSHOT</version>
 7 | 	</parent>
 8 | 	<modelVersion>4.0.0</modelVersion>
 9 | 	<groupId>net.cheney.mdns</groupId>
10 | 	<artifactId>mdns-core</artifactId>
11 | 	<name>mdns core</name>
12 | 	<version>0.0.1-SNAPSHOT</version>
13 | 
14 | 	<dependencies>
15 | 		<dependency>
16 | 			<groupId>commons-lang</groupId>
17 | 			<artifactId>commons-lang</artifactId>
18 | 		</dependency>
19 | 	</dependencies>
20 | </project>


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/mdns-core/src/main/java/net/cheney/mdns/DNSQuery.java:
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 1 | package net.cheney.mdns;
 2 | 
 3 | public final class DNSQuery extends DNSMessage {
 4 | 
 5 | 	private final String name;
 6 | 	private final Record.Type type;
 7 | 	private final Record.Class clazz;
 8 | 
 9 | 	public DNSQuery(String name, Record.Type type, Record.Class clazz) {
10 | 		this.name = name;
11 | 		this.type = type;
12 | 		this.clazz = clazz;
13 | 	}
14 | 	
15 | 	@Override
16 | 	public String toString() {
17 | 		return String.format("%s [type %s, class %s]", name, type, clazz);
18 | 	}
19 | 	
20 | 	public String name() {
21 | 		return name;
22 | 	}
23 | 	
24 | 	public Record.Type type() {
25 | 		return type;
26 | 	}
27 | 
28 | 	public Record.Class clazz() {
29 | 		return clazz;
30 | 	}
31 | 
32 | }
33 | 


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/mdns-core/src/main/java/net/cheney/mdns/MdnsListener.java:
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 1 | package net.cheney.mdns;
 2 | 
 3 | import java.io.IOException;
 4 | import java.net.DatagramPacket;
 5 | import java.net.InetAddress;
 6 | import java.net.MulticastSocket;
 7 | import java.nio.ByteBuffer;
 8 | 
 9 | public class MdnsListener implements Runnable {
10 | 
11 | 	private final MulticastSocket socket;
12 | 
13 | 	public MdnsListener() throws IOException {
14 | 		socket = new MulticastSocket(5353);
15 | 		socket.joinGroup(InetAddress.getByName("224.0.0.251"));
16 | 	}
17 | 
18 | 	public void run() {
19 | 		try {
20 | 			for( ;; ) {
21 | 				DatagramPacket p = new DatagramPacket(new byte[512], 512);
22 | 				socket.receive(p);
23 | 				ByteBuffer b = ByteBuffer.wrap(p.getData(), p.getOffset(), p.getLength());
24 | 				DNSResponse response = DNSResponseParser.parse(b);
25 | 				System.out.println(response);
26 | 			}
27 | 		} catch (IOException e) {
28 | 			e.printStackTrace();
29 | 		} finally {
30 | 			socket.close();
31 | 		}
32 | 	}
33 | 	
34 | 	public static void main(String[] args) throws IOException {
35 | 		Thread t = new Thread(new MdnsListener());
36 | 		t.run();
37 | 	}
38 | }
39 | 


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/pom.xml:
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 1 | <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 2 | 	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
 3 | 	<modelVersion>4.0.0</modelVersion>
 4 | 	<groupId>net.cheney.mdns</groupId>
 5 | 	<artifactId>mdns</artifactId>
 6 | 	<name>mdns</name>
 7 | 	<version>0.0.1-SNAPSHOT</version>
 8 | 	<description>Multicast DNS</description>
 9 | 
10 | 	<packaging>pom</packaging>
11 | 
12 | 	<properties>
13 | 		<maven.compile.source>1.6</maven.compile.source>
14 | 		<maven.compile.target>${maven.compile.source}</maven.compile.target>
15 | 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
16 | 	</properties>
17 | 
18 | 	<modules>
19 | 		<module>mdns-core</module>
20 | 	</modules>
21 | 
22 | 	<dependencyManagement>
23 | 		<dependencies>
24 | 			<dependency>
25 | 				<groupId>junit</groupId>
26 | 				<artifactId>junit</artifactId>
27 | 				<version>4.13.1</version>
28 | 			</dependency>
29 | 			<dependency>
30 | 				<groupId>commons-lang</groupId>
31 | 				<artifactId>commons-lang</artifactId>
32 | 				<version>2.4</version>
33 | 			</dependency>
34 | 		</dependencies>
35 | 	</dependencyManagement>
36 | 
37 | 
38 | 	<build>
39 | 		<plugins>
40 | 			<plugin>
41 | 				<artifactId>maven-compiler-plugin</artifactId>
42 | 				<configuration>
43 | 					<source>${maven.compile.source}</source>
44 | 					<target>${maven.compile.target}</target>
45 | 				</configuration>
46 | 			</plugin>
47 | 		</plugins>
48 | 	</build>
49 | 	
50 | </project>


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/mdns-core/src/main/java/net/cheney/mdns/DNSRequestBuilder.java:
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 1 | package net.cheney.mdns;
 2 | 
 3 | import java.nio.ByteBuffer;
 4 | 
 5 | import org.apache.commons.lang.StringUtils;
 6 | 
 7 | public class DNSRequestBuilder {
 8 | 
 9 | 	private DNSRequestBuilder() { };
10 | 	
11 | 	/*
12 | 	 * The header contains the following fields:
13 | 
14 |                                     1  1  1  1  1  1
15 |       0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
16 |     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
17 |     |                      ID                       |
18 |     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
19 |     |QR|   Opcode  |AA|TC|RD|RA|   Z    |   RCODE   |
20 |     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
21 |     |                    QDCOUNT                    |
22 |     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
23 |     |                    ANCOUNT                    |
24 |     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
25 |     |                    NSCOUNT                    |
26 |     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
27 |     |                    ARCOUNT                    |
28 |     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
29 | 	 */
30 | 	public static ByteBuffer buildRequest(DNSQuery query) {
31 | 		ByteBuffer request = ByteBuffer.allocate(512);
32 | 		short id = 1;
33 | 		request.putShort(id);
34 | 		short flags = 0;
35 | 		request.putShort(flags);
36 | 		short qdcount = 1;
37 | 		request.putShort(qdcount);
38 | 		short ancount = 0;
39 | 		request.putShort(ancount);
40 | 		short nscount = 0;
41 | 		request.putShort(nscount);
42 | 		short arcount = 0;
43 | 		request.putShort(arcount);
44 | 		
45 | 		request.put(toQName(query.name()));
46 | 		
47 | 		request.putShort(query.type().value());
48 | 		request.putShort(query.clazz().value());
49 | 		return (ByteBuffer) request.flip();
50 | 	}
51 | 	
52 | 	private static ByteBuffer toQName(String string) {
53 | 		ByteBuffer buffer = ByteBuffer.allocate(512);
54 | 		for(String label : StringUtils.split(string, '.')) {
55 | 			buffer.put((byte) label.length());
56 | 			for(char c : label.toCharArray()) {
57 | 				buffer.put((byte) c);
58 | 			}
59 | 		}
60 | 		buffer.put((byte) 0);
61 | 		return (ByteBuffer) buffer.flip();
62 | 	}
63 | }
64 | 


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/mdns-core/src/main/java/net/cheney/mdns/Record.java:
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  1 | package net.cheney.mdns;
  2 | 
  3 | public abstract class Record {
  4 | 
  5 | 	private final String name;
  6 | 	private final Type type;
  7 | 	private final Class clazz;
  8 | 	private final int ttl;
  9 | 	
 10 | 	public Record(Type type, Class recordClass, String name, int ttl) {
 11 | 		this.name = name;
 12 | 		this.type = type;
 13 | 		this.clazz = recordClass;
 14 | 		this.ttl = ttl;
 15 | 	}
 16 | 	
 17 | 	@Override
 18 | 	public String toString() {
 19 | 		return String.format("%s ttl: %d [type %s, clazz %s]", name, ttl, type, clazz);
 20 | 	}
 21 | 	
 22 | 	public final String name() {
 23 | 		return name;
 24 | 	}
 25 | 	
 26 | 	public final Type type() {
 27 | 		return type;
 28 | 	}
 29 | 	
 30 | 	public final Class clazz() {
 31 | 		return clazz;
 32 | 	}
 33 | 
 34 | 	public enum Class {
 35 | 
 36 | 		IN(1),
 37 | 		CS(2),
 38 | 		CH(3),
 39 | 		HS(4),
 40 | 		
 41 | 		ANY(255)
 42 | 		;
 43 | 		
 44 | 		private final short value;
 45 | 
 46 | 		Class(int value) {
 47 | 			this.value = (short) value;
 48 | 		}
 49 | 		
 50 | 		public static Class parse(short i) {
 51 | 			for(Class t : values()) {
 52 | 				if(t.value == (i & 0x00ff)) return t;
 53 | 			}
 54 | 			return null;
 55 | 		}
 56 | 
 57 | 		public short value() {
 58 | 			return value;
 59 | 		}
 60 | 	}
 61 | 	
 62 | 	// see http://en.wikipedia.org/wiki/List_of_DNS_record_types
 63 | 
 64 | 	public enum Type {
 65 | 
 66 | 		A(1),
 67 | 		AAAA(28),
 68 | 		AFSDB(18),
 69 | 		CERT(37),
 70 | 		DHCID(49),
 71 | 		DLV(32769),
 72 | 		DNAME(39),
 73 | 		DNSKEY(48),
 74 | 		DS(43),
 75 | 		HIP(55),
 76 | 		IPSECKEY(45),
 77 | 		KEY(25),
 78 | 		LOC(29),
 79 | 		NAPTR(35),
 80 | 		NSEC(47),
 81 | 		NSEC3(50),
 82 | 		NSEC3PARAM(51),
 83 | 		RRSIG(46),
 84 | 		SIG(24),
 85 | 		SPF(99),
 86 | 		SRV(33),
 87 | 		SSHFP(44),
 88 | 		TA(32768),
 89 | 		NS(2),
 90 | 		MD(3),
 91 | 		MF(4),
 92 | 		CNAME(5),
 93 | 		SOA(6),
 94 | 		MB(7),
 95 | 		MG(8),
 96 | 		MR(9),
 97 | 		NULL(10),
 98 | 		WKS(11),
 99 | 		PTR(12),
100 | 		HINFO(13),
101 | 		MINFO(14),
102 | 		MX(15),
103 | 		TXT(16),
104 | 		
105 | 		OPT(41),
106 | 		
107 | 		TKEY(249),
108 | 		TSIG(250),
109 | 		
110 | 		IXFR(251),
111 | 		AXFR(252),
112 | 		MAILB(253),
113 | 		MAILA(254),
114 | 		
115 | 		ANY(255)
116 | 		;
117 | 		
118 | 		private final short value;
119 | 
120 | 		Type(int value) {
121 | 			this.value = (short) value;
122 | 		}
123 | 		
124 | 		public static Type parse(short i) {
125 | 			for(Type t : values()) {
126 | 				if(t.value == i) return t;
127 | 			}
128 | 			return null;
129 | 		}
130 | 
131 | 		public short value() {
132 | 			return value;
133 | 		}
134 | 	}
135 | 
136 | 	
137 | }
138 | 


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/mdns-core/src/main/java/net/cheney/mdns/DNSResponseParser.java:
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 1 | package net.cheney.mdns;
 2 | 
 3 | import java.nio.ByteBuffer;
 4 | import java.util.ArrayList;
 5 | import java.util.List;
 6 | 
 7 | import net.cheney.mdns.DNSResponse.Builder;
 8 | 
 9 | import org.apache.commons.lang.StringUtils;
10 | 
11 | public class DNSResponseParser {
12 | 
13 | 	private DNSResponseParser() { };
14 | 	
15 | 	public static DNSResponse parse(ByteBuffer buffer) {
16 | 		short id = buffer.getShort();
17 | 		short flags = buffer.getShort();
18 | 		short qdcount = buffer.getShort(), ancount = buffer.getShort(), nscount = buffer.getShort(), arcount = buffer.getShort();
19 | 		
20 | 		Builder builder = DNSResponse.builder(id, flags);
21 | 		
22 | 		for(int i = 0 ; i < qdcount ; i++ ) {
23 | 			DNSQuery question = parseQuestion(buffer);
24 | 			builder.addQuestion(question);
25 | 		}
26 | 
27 | 		for(int i = 0 ; i < ancount ; i++ ) {
28 | 			Record answer = parseResponseRecord(buffer);
29 | 			builder.addAnswer(answer);
30 | 		}
31 | 
32 | 		for(int i = 0 ; i < nscount ; i++ ) {
33 | 			Record nameserver = parseResponseRecord(buffer);
34 | 			builder.addNameserver(nameserver);
35 | 		}
36 | 
37 | 		for(int i = 0 ; i < arcount ; i++ ) {
38 | 			Record additionalRecord = parseResponseRecord(buffer);
39 | 			builder.addAdditionalRecord(additionalRecord);
40 | 		}
41 | 		
42 | 		return builder.build();
43 | 	}
44 | 
45 | 	private static DNSQuery parseQuestion(ByteBuffer buffer) {
46 | 		String name = parseName(buffer);
47 | 		Record.Type type = Record.Type.parse(buffer.getShort());
48 | 		Record.Class clazz = Record.Class.parse(buffer.getShort());
49 | 		return new DNSQuery(name, type, clazz);
50 | 	}
51 | 
52 | 	private static String parseName(ByteBuffer buffer) {
53 | 		return StringUtils.join(parseName0(buffer), '.');
54 | 	}
55 | 	
56 | 	private static List<String> parseName0(ByteBuffer buffer) {
57 | 		List<String> labels = new ArrayList<String>();
58 | 		for( ;; ) {
59 | 			byte length = buffer.get();
60 | 			if(length != 0) {
61 | 				if ((length & 192) == 192) {
62 | 					// inelegant support for pointers
63 | 					int offset = (length & 63);
64 | 					offset =+ (buffer.get() & 0xff);
65 | 					labels.addAll(parseName0((ByteBuffer) buffer.duplicate().position(offset)));
66 | 					break;
67 | 				} else {
68 | 					StringBuilder label = new StringBuilder(63);
69 | 					for(int i = 0 ; i < length ; i++) {
70 | 						label.append((char)buffer.get());
71 | 					}
72 | 					labels.add(label.toString());
73 | 				}
74 | 			} else {
75 | 				break;
76 | 			}
77 | 		}
78 | 		return labels;
79 | 	}
80 | 
81 | 	private static Record parseResponseRecord(ByteBuffer buffer) {
82 | 		String name = parseName(buffer);
83 | 		short type = buffer.getShort();
84 | 		short clazz = buffer.getShort();
85 | 		int ttl = buffer.getInt();
86 | 		short rdlength = buffer.getShort();
87 | 		ByteBuffer rdata = (ByteBuffer) buffer.duplicate().position(buffer.position()).limit(buffer.position() + rdlength);
88 | 		buffer.position(buffer.position() + rdlength);
89 | 		return new CachedRecord(Record.Type.parse(type), Record.Class.parse(clazz), name, ttl);
90 | 	}
91 | }
92 | 


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/mdns-core/src/main/java/net/cheney/mdns/DNSResponse.java:
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  1 | package net.cheney.mdns;
  2 | 
  3 | import java.util.ArrayList;
  4 | import java.util.List;
  5 | 
  6 | import static java.lang.String.format;
  7 | 
  8 | public class DNSResponse extends DNSMessage {
  9 | 
 10 | 	private final short id;
 11 | 	private final short flags;
 12 | 	private final List<DNSQuery> questions;
 13 | 	private final List<Record> answers, nameservers, additionalRecords;
 14 | 
 15 | 	DNSResponse(short id, short flags, List<DNSQuery> questions,
 16 | 			List<Record> answers, List<Record> nameservers,
 17 | 			List<Record> additionalRecords) {
 18 | 		this.id = id;
 19 | 		this.flags = flags;
 20 | 		this.questions = questions;
 21 | 		this.answers = answers;
 22 | 		this.nameservers = nameservers;
 23 | 		this.additionalRecords = additionalRecords;
 24 | 	}
 25 | 	
 26 | 	public static Builder builder(short id, short flags) {
 27 | 		return new Builder(id, flags);
 28 | 	}
 29 | 
 30 | 	public static class Builder {
 31 | 		
 32 | 		private final short id, flags;
 33 | 		private final List<DNSQuery> questions;
 34 | 		private final List<Record> answers, nameservers, additionalRecords;
 35 | 		
 36 | 		Builder(short id, short flags) {
 37 | 			this.id = id;
 38 | 			this.flags = flags;
 39 | 			questions = new ArrayList<DNSQuery>();
 40 | 			answers = new ArrayList<Record>();
 41 | 			nameservers = new ArrayList<Record>();
 42 | 			additionalRecords = new ArrayList<Record>();
 43 | 		}
 44 | 
 45 | 		public void addQuestion(DNSQuery question) {
 46 | 			questions.add(question);			
 47 | 		}
 48 | 
 49 | 		public DNSResponse build() {
 50 | 			return new DNSResponse(id, flags, questions, answers, nameservers, additionalRecords);
 51 | 		}
 52 | 
 53 | 		public void addAnswer(Record answer) {
 54 | 			answers.add(answer);			
 55 | 		}
 56 | 
 57 | 		public void addNameserver(Record nameserver) {
 58 | 			nameservers.add(nameserver);
 59 | 		}
 60 | 
 61 | 		public void addAdditionalRecord(Record additionalRecord) {
 62 | 			additionalRecords.add(additionalRecord);
 63 | 		}
 64 | 	}
 65 | 	
 66 | 	@Override
 67 | 	public String toString() {
 68 | 		StringBuilder sb = new StringBuilder(512);
 69 | 		sb.append(format("Transaction ID: %d\n", id()));
 70 | 		sb.append(format("Flags: %d\n", flags()));
 71 | 		sb.append(format("Questions: %s\n", questions()));
 72 | 		
 73 | 		sb.append(format("Answers: %s\n", answers()));
 74 | 		sb.append(format("Authority: %s\n", nameservers()));
 75 | 		sb.append(format("Additional: %s\n", additionalRecords()));
 76 | 		return sb.toString();
 77 | 	}
 78 | 
 79 | 	public List<DNSQuery> questions() {
 80 | 		return questions;
 81 | 	}
 82 | 	
 83 | 	public List<Record> answers() {
 84 | 		return answers;
 85 | 	}
 86 | 	
 87 | 	public List<Record> nameservers() {
 88 | 		return nameservers;
 89 | 	}
 90 | 	
 91 | 	public List<Record> additionalRecords() {
 92 | 		return additionalRecords;
 93 | 	}
 94 | 
 95 | 	private int flags() {
 96 | 		return flags;
 97 | 	}
 98 | 	
 99 | 	public boolean isTruncated() {
100 | 		return ((flags & 64) == 64);
101 | 	}
102 | 
103 | 	private int id() {
104 | 		return id;
105 | 	}
106 | }
107 | 


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