DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Mercurial (5b81998bb7ab)

VCS Links

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560
""" Multicast DNS Service Discovery for Python, v0.12
    Copyright (C) 2003, Paul Scott-Murphy

    This module provides a framework for the use of DNS Service Discovery
    using IP multicast.  It has been tested against the JRendezvous
    implementation from <a href="http://strangeberry.com">StrangeBerry</a>,
    and against the mDNSResponder from Mac OS X 10.3.8.

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
    
"""

"""0.12 update - allow selection of binding interface
         typo fix - Thanks A. M. Kuchlingi
         removed all use of word 'Rendezvous' - this is an API change"""

"""0.11 update - correction to comments for addListener method
                 support for new record types seen from OS X
                  - IPv6 address
                  - hostinfo
                 ignore unknown DNS record types
                 fixes to name decoding
                 works alongside other processes using port 5353 (e.g. on Mac OS X)
                 tested against Mac OS X 10.3.2's mDNSResponder
                 corrections to removal of list entries for service browser"""

"""0.10 update - Jonathon Paisley contributed these corrections:
                 always multicast replies, even when query is unicast
                 correct a pointer encoding problem
                 can now write records in any order
                 traceback shown on failure
                 better TXT record parsing
                 server is now separate from name
                 can cancel a service browser

                 modified some unit tests to accommodate these changes"""

"""0.09 update - remove all records on service unregistration
                 fix DOS security problem with readName"""

"""0.08 update - changed licensing to LGPL"""

"""0.07 update - faster shutdown on engine
                 pointer encoding of outgoing names
                 ServiceBrowser now works
                 new unit tests"""

"""0.06 update - small improvements with unit tests
                 added defined exception types
                 new style objects
                 fixed hostname/interface problem
                 fixed socket timeout problem
                 fixed addServiceListener() typo bug
                 using select() for socket reads
                 tested on Debian unstable with Python 2.2.2"""

"""0.05 update - ensure case insensitivty on domain names
                 support for unicast DNS queries"""

"""0.04 update - added some unit tests
                 added __ne__ adjuncts where required
                 ensure names end in '.local.'
                 timeout on receiving socket for clean shutdown"""

__author__ = "Paul Scott-Murphy"
__email__ = "paul at scott dash murphy dot com"
__version__ = "0.12"

import string
import time
import struct
import socket
import threading
import select
import traceback

__all__ = ["Zeroconf", "ServiceInfo", "ServiceBrowser"]

# hook for threads

globals()['_GLOBAL_DONE'] = 0

# Some timing constants

_UNREGISTER_TIME = 125
_CHECK_TIME = 175
_REGISTER_TIME = 225
_LISTENER_TIME = 200
_BROWSER_TIME = 500

# Some DNS constants
    
_MDNS_ADDR = '224.0.0.251'
_MDNS_PORT = 5353;
_DNS_PORT = 53;
_DNS_TTL = 60 * 60; # one hour default TTL

_MAX_MSG_TYPICAL = 1460 # unused
_MAX_MSG_ABSOLUTE = 8972

_FLAGS_QR_MASK = 0x8000 # query response mask
_FLAGS_QR_QUERY = 0x0000 # query
_FLAGS_QR_RESPONSE = 0x8000 # response

_FLAGS_AA = 0x0400 # Authorative answer
_FLAGS_TC = 0x0200 # Truncated
_FLAGS_RD = 0x0100 # Recursion desired
_FLAGS_RA = 0x8000 # Recursion available

_FLAGS_Z = 0x0040 # Zero
_FLAGS_AD = 0x0020 # Authentic data
_FLAGS_CD = 0x0010 # Checking disabled

_CLASS_IN = 1
_CLASS_CS = 2
_CLASS_CH = 3
_CLASS_HS = 4
_CLASS_NONE = 254
_CLASS_ANY = 255
_CLASS_MASK = 0x7FFF
_CLASS_UNIQUE = 0x8000

_TYPE_A = 1
_TYPE_NS = 2
_TYPE_MD = 3
_TYPE_MF = 4
_TYPE_CNAME = 5
_TYPE_SOA = 6
_TYPE_MB = 7
_TYPE_MG = 8
_TYPE_MR = 9
_TYPE_NULL = 10
_TYPE_WKS = 11
_TYPE_PTR = 12
_TYPE_HINFO = 13
_TYPE_MINFO = 14
_TYPE_MX = 15
_TYPE_TXT = 16
_TYPE_AAAA = 28
_TYPE_SRV = 33
_TYPE_ANY =  255

# Mapping constants to names

_CLASSES = { _CLASS_IN : "in",
             _CLASS_CS : "cs",
             _CLASS_CH : "ch",
             _CLASS_HS : "hs",
             _CLASS_NONE : "none",
             _CLASS_ANY : "any" }

_TYPES = { _TYPE_A : "a",
           _TYPE_NS : "ns",
           _TYPE_MD : "md",
           _TYPE_MF : "mf",
           _TYPE_CNAME : "cname",
           _TYPE_SOA : "soa",
           _TYPE_MB : "mb",
           _TYPE_MG : "mg",
           _TYPE_MR : "mr",
           _TYPE_NULL : "null",
           _TYPE_WKS : "wks",
           _TYPE_PTR : "ptr",
           _TYPE_HINFO : "hinfo",
           _TYPE_MINFO : "minfo",
           _TYPE_MX : "mx",
           _TYPE_TXT : "txt",
           _TYPE_AAAA : "quada",
           _TYPE_SRV : "srv",
           _TYPE_ANY : "any" }

# utility functions

def currentTimeMillis():
    """Current system time in milliseconds"""
    return time.time() * 1000

# Exceptions

class NonLocalNameException(Exception):
    pass

class NonUniqueNameException(Exception):
    pass

class NamePartTooLongException(Exception):
    pass

class AbstractMethodException(Exception):
    pass

class BadTypeInNameException(Exception):
    pass

# implementation classes

class DNSEntry(object):
    """A DNS entry"""
    
    def __init__(self, name, type, clazz):
        self.key = string.lower(name)
        self.name = name
        self.type = type
        self.clazz = clazz & _CLASS_MASK
        self.unique = (clazz & _CLASS_UNIQUE) != 0

    def __eq__(self, other):
        """Equality test on name, type, and class"""
        if isinstance(other, DNSEntry):
            return self.name == other.name and self.type == other.type and self.clazz == other.clazz
        return 0

    def __ne__(self, other):
        """Non-equality test"""
        return not self.__eq__(other)

    def getClazz(self, clazz):
        """Class accessor"""
        try:
            return _CLASSES[clazz]
        except:
            return "?(%s)" % (clazz)

    def getType(self, type):
        """Type accessor"""
        try:
            return _TYPES[type]
        except:
            return "?(%s)" % (type)

    def toString(self, hdr, other):
        """String representation with additional information"""
        result = "%s[%s,%s" % (hdr, self.getType(self.type), self.getClazz(self.clazz))
        if self.unique:
            result += "-unique,"
        else:
            result += ","
        result += self.name
        if other is not None:
            result += ",%s]" % (other)
        else:
            result += "]"
        return result

class DNSQuestion(DNSEntry):
    """A DNS question entry"""
    
    def __init__(self, name, type, clazz):
        if not name.endswith(".local."):
            raise NonLocalNameException
        DNSEntry.__init__(self, name, type, clazz)

    def answeredBy(self, rec):
        """Returns true if the question is answered by the record"""
        return self.clazz == rec.clazz and (self.type == rec.type or self.type == _TYPE_ANY) and self.name == rec.name

    def __repr__(self):
        """String representation"""
        return DNSEntry.toString(self, "question", None)


class DNSRecord(DNSEntry):
    """A DNS record - like a DNS entry, but has a TTL"""
    
    def __init__(self, name, type, clazz, ttl):
        DNSEntry.__init__(self, name, type, clazz)
        self.ttl = ttl
        self.created = currentTimeMillis()

    def __eq__(self, other):
        """Tests equality as per DNSRecord"""
        if isinstance(other, DNSRecord):
            return DNSEntry.__eq__(self, other)
        return 0

    def suppressedBy(self, msg):
        """Returns true if any answer in a message can suffice for the
        information held in this record."""
        for record in msg.answers:
            if self.suppressedByAnswer(record):
                return 1
        return 0

    def suppressedByAnswer(self, other):
        """Returns true if another record has same name, type and class,
        and if its TTL is at least half of this record's."""
        if self == other and other.ttl > (self.ttl / 2):
            return 1
        return 0

    def getExpirationTime(self, percent):
        """Returns the time at which this record will have expired
        by a certain percentage."""
        return self.created + (percent * self.ttl * 10)

    def getRemainingTTL(self, now):
        """Returns the remaining TTL in seconds."""
        return max(0, (self.getExpirationTime(100) - now) / 1000)

    def isExpired(self, now):
        """Returns true if this record has expired."""
        return self.getExpirationTime(100) <= now

    def isStale(self, now):
        """Returns true if this record is at least half way expired."""
        return self.getExpirationTime(50) <= now

    def resetTTL(self, other):
        """Sets this record's TTL and created time to that of
        another record."""
        self.created = other.created
        self.ttl = other.ttl

    def write(self, out):
        """Abstract method"""
        raise AbstractMethodException

    def toString(self, other):
        """String representation with addtional information"""
        arg = "%s/%s,%s" % (self.ttl, self.getRemainingTTL(currentTimeMillis()), other)
        return DNSEntry.toString(self, "record", arg)

class DNSAddress(DNSRecord):
    """A DNS address record"""
    
    def __init__(self, name, type, clazz, ttl, address):
        DNSRecord.__init__(self, name, type, clazz, ttl)
        self.address = address

    def write(self, out):
        """Used in constructing an outgoing packet"""
        out.writeString(self.address, len(self.address))

    def __eq__(self, other):
        """Tests equality on address"""
        if isinstance(other, DNSAddress):
            return self.address == other.address
        return 0

    def __repr__(self):
        """String representation"""
        try:
            return socket.inet_ntoa(self.address)
        except:
            return self.address

class DNSHinfo(DNSRecord):
    """A DNS host information record"""

    def __init__(self, name, type, clazz, ttl, cpu, os):
        DNSRecord.__init__(self, name, type, clazz, ttl)
        self.cpu = cpu
        self.os = os

    def write(self, out):
        """Used in constructing an outgoing packet"""
        out.writeString(self.cpu, len(self.cpu))
        out.writeString(self.os, len(self.os))

    def __eq__(self, other):
        """Tests equality on cpu and os"""
        if isinstance(other, DNSHinfo):
            return self.cpu == other.cpu and self.os == other.os
        return 0

    def __repr__(self):
        """String representation"""
        return self.cpu + " " + self.os
    
class DNSPointer(DNSRecord):
    """A DNS pointer record"""
    
    def __init__(self, name, type, clazz, ttl, alias):
        DNSRecord.__init__(self, name, type, clazz, ttl)
        self.alias = alias

    def write(self, out):
        """Used in constructing an outgoing packet"""
        out.writeName(self.alias)

    def __eq__(self, other):
        """Tests equality on alias"""
        if isinstance(other, DNSPointer):
            return self.alias == other.alias
        return 0

    def __repr__(self):
        """String representation"""
        return self.toString(self.alias)

class DNSText(DNSRecord):
    """A DNS text record"""
    
    def __init__(self, name, type, clazz, ttl, text):
        DNSRecord.__init__(self, name, type, clazz, ttl)
        self.text = text

    def write(self, out):
        """Used in constructing an outgoing packet"""
        out.writeString(self.text, len(self.text))

    def __eq__(self, other):
        """Tests equality on text"""
        if isinstance(other, DNSText):
            return self.text == other.text
        return 0

    def __repr__(self):
        """String representation"""
        if len(self.text) > 10:
            return self.toString(self.text[:7] + "...")
        else:
            return self.toString(self.text)

class DNSService(DNSRecord):
    """A DNS service record"""
    
    def __init__(self, name, type, clazz, ttl, priority, weight, port, server):
        DNSRecord.__init__(self, name, type, clazz, ttl)
        self.priority = priority
        self.weight = weight
        self.port = port
        self.server = server

    def write(self, out):
        """Used in constructing an outgoing packet"""
        out.writeShort(self.priority)
        out.writeShort(self.weight)
        out.writeShort(self.port)
        out.writeName(self.server)

    def __eq__(self, other):
        """Tests equality on priority, weight, port and server"""
        if isinstance(other, DNSService):
            return self.priority == other.priority and self.weight == other.weight and self.port == other.port and self.server == other.server
        return 0

    def __repr__(self):
        """String representation"""
        return self.toString("%s:%s" % (self.server, self.port))

class DNSIncoming(object):
    """Object representation of an incoming DNS packet"""
    
    def __init__(self, data):
        """Constructor from string holding bytes of packet"""
        self.offset = 0
        self.data = data
        self.questions = []
        self.answers = []
        self.numQuestions = 0
        self.numAnswers = 0
        self.numAuthorities = 0
        self.numAdditionals = 0
        
        self.readHeader()
        self.readQuestions()
        self.readOthers()

    def readHeader(self):
        """Reads header portion of packet"""
        format = '!HHHHHH'
        length = struct.calcsize(format)
        info = struct.unpack(format, self.data[self.offset:self.offset+length])
        self.offset += length

        self.id = info[0]
        self.flags = info[1]
        self.numQuestions = info[2]
        self.numAnswers = info[3]
        self.numAuthorities = info[4]
        self.numAdditionals = info[5]

    def readQuestions(self):
        """Reads questions section of packet"""
        format = '!HH'
        length = struct.calcsize(format)
        for i in range(0, self.numQuestions):
            name = self.readName()
            info = struct.unpack(format, self.data[self.offset:self.offset+length])
            self.offset += length
            
            question = DNSQuestion(name, info[0], info[1])
            self.questions.append(question)

    def readInt(self):
        """Reads an integer from the packet"""
        format = '!I'
        length = struct.calcsize(format)
        info = struct.unpack(format, self.data[self.offset:self.offset+length])
        self.offset += length
        return info[0]

    def readCharacterString(self):
        """Reads a character string from the packet"""
        length = ord(self.data[self.offset])
        self.offset += 1
        return self.readString(length)

    def readString(self, len):
        """Reads a string of a given length from the packet"""
        format = '!' + str(len) + 's'
        length =  struct.calcsize(format)
        info = struct.unpack(format, self.data[self.offset:self.offset+length])
        self.offset += length
        return info[0]

    def readUnsignedShort(self):
        """Reads an unsigned short from the packet"""
        format = '!H'
        length = struct.calcsize(format)
        info = struct.unpack(format, self.data[self.offset:self.offset+length])
        self.offset += length
        return info[0]

    def readOthers(self):
        """Reads the answers, authorities and additionals section of the packet"""
        format = '!HHiH'
        length = struct.calcsize(format)
        n = self.numAnswers + self.numAuthorities + self.numAdditionals
        for i in range(0, n):
            domain = self.readName()
            info = struct.unpack(format, self.data[self.offset:self.offset+length])
            self.offset += length

            rec = None
            if info[0] == _TYPE_A:
                rec = DNSAddress(domain, info[0], info[1], info[2], self.readString(4))
            elif info[0] == _TYPE_CNAME or info[0] == _TYPE_PTR:
                rec = DNSPointer(domain, info[0], info[1], info[2], self.readName())
            elif info[0] == _TYPE_TXT:
                rec = DNSText(domain, info[0], info[1], info[2], self.readString(info[3]))
            elif info[0] == _TYPE_SRV:
                rec = DNSService(domain, info[0], info[1], info[2], self.readUnsignedShort(), self.readUnsignedShort(), self.readUnsignedShort(), self.readName())
            elif info[0] == _TYPE_HINFO:
                rec = DNSHinfo(domain, info[0], info[1], info[2], self.readCharacterString(), self.readCharacterString())
            elif info[0] == _TYPE_AAAA:
                rec = DNSAddress(domain, info[0], info[1], info[2], self.readString(16))
            else:
                # Try to ignore types we don't know about
                # this may mean the rest of the name is
                # unable to be parsed, and may show errors
                # so this is left for debugging.  New types
                # encountered need to be parsed properly.
                #
                #print "UNKNOWN TYPE = " + str(info[0])
                #raise BadTypeInNameException
                pass

            if rec is not None:
                self.answers.append(rec)
                
    def isQuery(self):
        """Returns true if this is a query"""
        return (self.flags & _FLAGS_QR_MASK) == _FLAGS_QR_QUERY

    def isResponse(self):
        """Returns true if this is a response"""
        return (self.flags & _FLAGS_QR_MASK) == _FLAGS_QR_RESPONSE

    def readUTF(self, offset, len):
        """Reads a UTF-8 string of a given length from the packet"""
        result = self.data[offset:offset+len].decode('utf-8')
        return result
        
    def readName(self):
        """Reads a domain name from the packet"""
        result = ''
        off = self.offset
        next = -1
        first = off

        while 1:
            len = ord(self.data[off])
            off += 1
            if len == 0:
                break
            t = len & 0xC0
            if t == 0x00:
                result = ''.join((result, self.readUTF(off, len) + '.'))
                off += len
            elif t == 0xC0:
                if next < 0:
                    next = off + 1
                off = ((len & 0x3F) << 8) | ord(self.data[off])
                if off >= first:
                    raise "Bad domain name (circular) at " + str(off)
                first = off
            else:
                raise "Bad domain name at " + str(off)

        if next >= 0:
            self.offset = next
        else:
            self.offset = off

        return result
    
        
class DNSOutgoing(object):
    """Object representation of an outgoing packet"""
    
    def __init__(self, flags, multicast = 1):
        self.finished = 0
        self.id = 0
        self.multicast = multicast
        self.flags = flags
        self.names = {}
        self.data = []
        self.size = 12
        
        self.questions = []
        self.answers = []
        self.authorities = []
        self.additionals = []

    def addQuestion(self, record):
        """Adds a question"""
        self.questions.append(record)

    def addAnswer(self, inp, record):
        """Adds an answer"""
        if not record.suppressedBy(inp):
            self.addAnswerAtTime(record, 0)

    def addAnswerAtTime(self, record, now):
        """Adds an answer if if does not expire by a certain time"""
        if record is not None:
            if now == 0 or not record.isExpired(now):
                self.answers.append((record, now))

    def addAuthorativeAnswer(self, record):
        """Adds an authoritative answer"""
        self.authorities.append(record)

    def addAdditionalAnswer(self, record):
        """Adds an additional answer"""
        self.additionals.append(record)

    def writeByte(self, value):
        """Writes a single byte to the packet"""
        format = '!c'
        self.data.append(struct.pack(format, chr(value)))
        self.size += 1

    def insertShort(self, index, value):
        """Inserts an unsigned short in a certain position in the packet"""
        format = '!H'
        self.data.insert(index, struct.pack(format, value))
        self.size += 2
        
    def writeShort(self, value):
        """Writes an unsigned short to the packet"""
        format = '!H'
        self.data.append(struct.pack(format, value))
        self.size += 2

    def writeInt(self, value):
        """Writes an unsigned integer to the packet"""
        format = '!I'
        self.data.append(struct.pack(format, value))
        self.size += 4

    def writeString(self, value, length):
        """Writes a string to the packet"""
        format = '!' + str(length) + 's'
        self.data.append(struct.pack(format, value))
        self.size += length

    def writeUTF(self, s):
        """Writes a UTF-8 string of a given length to the packet"""
        utfstr = s.encode('utf-8')
        length = len(utfstr)
        if length > 64:
            raise NamePartTooLongException
        self.writeByte(length)
        self.writeString(utfstr, length)

    def writeName(self, name):
        """Writes a domain name to the packet"""

        try:
            # Find existing instance of this name in packet
            #
            index = self.names[name]
        except KeyError:
            # No record of this name already, so write it
            # out as normal, recording the location of the name
            # for future pointers to it.
            #
            self.names[name] = self.size
            parts = name.split('.')
            if parts[-1] == '':
                parts = parts[:-1]
            for part in parts:
                self.writeUTF(part)
            self.writeByte(0)
            return

        # An index was found, so write a pointer to it
        #
        self.writeByte((index >> 8) | 0xC0)
        self.writeByte(index)

    def writeQuestion(self, question):
        """Writes a question to the packet"""
        self.writeName(question.name)
        self.writeShort(question.type)
        self.writeShort(question.clazz)

    def writeRecord(self, record, now):
        """Writes a record (answer, authoritative answer, additional) to
        the packet"""
        self.writeName(record.name)
        self.writeShort(record.type)
        if record.unique and self.multicast:
            self.writeShort(record.clazz | _CLASS_UNIQUE)
        else:
            self.writeShort(record.clazz)
        if now == 0:
            self.writeInt(record.ttl)
        else:
            self.writeInt(record.getRemainingTTL(now))
        index = len(self.data)
        # Adjust size for the short we will write before this record
        #
        self.size += 2
        record.write(self)
        self.size -= 2
        
        length = len(''.join(self.data[index:]))
        self.insertShort(index, length) # Here is the short we adjusted for

    def packet(self):
        """Returns a string containing the packet's bytes

        No further parts should be added to the packet once this
        is done."""
        if not self.finished:
            self.finished = 1
            for question in self.questions:
                self.writeQuestion(question)
            for answer, time in self.answers:
                self.writeRecord(answer, time)
            for authority in self.authorities:
                self.writeRecord(authority, 0)
            for additional in self.additionals:
                self.writeRecord(additional, 0)
        
            self.insertShort(0, len(self.additionals))
            self.insertShort(0, len(self.authorities))
            self.insertShort(0, len(self.answers))
            self.insertShort(0, len(self.questions))
            self.insertShort(0, self.flags)
            if self.multicast:
                self.insertShort(0, 0)
            else:
                self.insertShort(0, self.id)
        return ''.join(self.data)


class DNSCache(object):
    """A cache of DNS entries"""
    
    def __init__(self):
        self.cache = {}

    def add(self, entry):
        """Adds an entry"""
        try:
            list = self.cache[entry.key]
        except:
            list = self.cache[entry.key] = []
        list.append(entry)

    def remove(self, entry):
        """Removes an entry"""
        try:
            list = self.cache[entry.key]
            list.remove(entry)
        except:
            pass

    def get(self, entry):
        """Gets an entry by key.  Will return None if there is no
        matching entry."""
        try:
            list = self.cache[entry.key]
            return list[list.index(entry)]
        except:
            return None

    def getByDetails(self, name, type, clazz):
        """Gets an entry by details.  Will return None if there is
        no matching entry."""
        entry = DNSEntry(name, type, clazz)
        return self.get(entry)

    def entriesWithName(self, name):
        """Returns a list of entries whose key matches the name."""
        try:
            return self.cache[name]
        except:
            return []

    def entries(self):
        """Returns a list of all entries"""
        def add(x, y): return x+y
        try:
            return reduce(add, self.cache.values())
        except:
            return []


class Engine(threading.Thread):
    """An engine wraps read access to sockets, allowing objects that
    need to receive data from sockets to be called back when the
    sockets are ready.

    A reader needs a handle_read() method, which is called when the socket
    it is interested in is ready for reading.

    Writers are not implemented here, because we only send short
    packets.
    """

    def __init__(self, zeroconf):
        threading.Thread.__init__(self)
        self.zeroconf = zeroconf
        self.readers = {} # maps socket to reader
        self.timeout = 5
        self.condition = threading.Condition()
        self.daemon = True
        self.start()

    def run(self):
        while not globals()['_GLOBAL_DONE']:
            rs = self.getReaders()
            if len(rs) == 0:
                # No sockets to manage, but we wait for the timeout
                # or addition of a socket
                #
                self.condition.acquire()
                self.condition.wait(self.timeout)
                self.condition.release()
            else:
                try:
                    rr, wr, er = select.select(rs, [], [], self.timeout)
                    for socket in rr:
                        try:
                            self.readers[socket].handle_read()
                        except:
                            # Ignore errors that occur on shutdown
                            pass
                except:
                    pass

    def getReaders(self):
        result = []
        self.condition.acquire()
        result = self.readers.keys()
        self.condition.release()
        return result
    
    def addReader(self, reader, socket):
        self.condition.acquire()
        self.readers[socket] = reader
        self.condition.notify()
        self.condition.release()

    def delReader(self, socket):
        self.condition.acquire()
        del(self.readers[socket])
        self.condition.notify()
        self.condition.release()

    def notify(self):
        self.condition.acquire()
        self.condition.notify()
        self.condition.release()

class Listener(object):
    """A Listener is used by this module to listen on the multicast
    group to which DNS messages are sent, allowing the implementation
    to cache information as it arrives.

    It requires registration with an Engine object in order to have
    the read() method called when a socket is availble for reading."""
    
    def __init__(self, zeroconf):
        self.zeroconf = zeroconf
        self.zeroconf.engine.addReader(self, self.zeroconf.socket)

    def handle_read(self):
        data, (addr, port) = self.zeroconf.socket.recvfrom(_MAX_MSG_ABSOLUTE)
        self.data = data
        msg = DNSIncoming(data)
        if msg.isQuery():
            # Always multicast responses
            #
            if port == _MDNS_PORT:
                self.zeroconf.handleQuery(msg, _MDNS_ADDR, _MDNS_PORT)
            # If it's not a multicast query, reply via unicast
            # and multicast
            #
            elif port == _DNS_PORT:
                self.zeroconf.handleQuery(msg, addr, port)
                self.zeroconf.handleQuery(msg, _MDNS_ADDR, _MDNS_PORT)
        else:
            self.zeroconf.handleResponse(msg)


class Reaper(threading.Thread):
    """A Reaper is used by this module to remove cache entries that
    have expired."""
    
    def __init__(self, zeroconf):
        threading.Thread.__init__(self)
        self.daemon = True
        self.zeroconf = zeroconf
        self.start()

    def run(self):
        while 1:
            self.zeroconf.wait(10 * 1000)
            if globals()['_GLOBAL_DONE']:
                return
            now = currentTimeMillis()
            for record in self.zeroconf.cache.entries():
                if record.isExpired(now):
                    self.zeroconf.updateRecord(now, record)
                    self.zeroconf.cache.remove(record)


class ServiceBrowser(threading.Thread):
    """Used to browse for a service of a specific type.

    The listener object will have its addService() and
    removeService() methods called when this browser
    discovers changes in the services availability."""
    
    def __init__(self, zeroconf, type, listener):
        """Creates a browser for a specific type"""
        threading.Thread.__init__(self)
        self.zeroconf = zeroconf
        self.type = type
        self.listener = listener
        self.services = {}
        self.nextTime = currentTimeMillis()
        self.delay = _BROWSER_TIME
        self.list = []
        self.daemon = True

        self.done = 0

        self.zeroconf.addListener(self, DNSQuestion(self.type, _TYPE_PTR, _CLASS_IN))
        self.start()

    def updateRecord(self, zeroconf, now, record):
        """Callback invoked by Zeroconf when new information arrives.

        Updates information required by browser in the Zeroconf cache."""
        if record.type == _TYPE_PTR and record.name == self.type:
            expired = record.isExpired(now)
            try:
                oldrecord = self.services[record.alias.lower()]
                if not expired:
                    oldrecord.resetTTL(record)
                else:
                    del(self.services[record.alias.lower()])
                    callback = lambda x: self.listener.removeService(x, self.type, record.alias)
                    self.list.append(callback)
                    return
            except:
                if not expired:
                    self.services[record.alias.lower()] = record
                    callback = lambda x: self.listener.addService(x, self.type, record.alias)
                    self.list.append(callback)

            expires = record.getExpirationTime(75)
            if expires < self.nextTime:
                self.nextTime = expires

    def cancel(self):
        self.done = 1
        self.zeroconf.notifyAll()

    def run(self):
        while 1:
            event = None
            now = currentTimeMillis()
            if len(self.list) == 0 and self.nextTime > now:
                self.zeroconf.wait(self.nextTime - now)
            if globals()['_GLOBAL_DONE'] or self.done:
                return
            now = currentTimeMillis()

            if self.nextTime <= now:
                out = DNSOutgoing(_FLAGS_QR_QUERY)
                out.addQuestion(DNSQuestion(self.type, _TYPE_PTR, _CLASS_IN))
                for record in self.services.values():
                    if not record.isExpired(now):
                        out.addAnswerAtTime(record, now)
                self.zeroconf.send(out)
                self.nextTime = now + self.delay
                self.delay = min(20 * 1000, self.delay * 2)

            if len(self.list) > 0:
                event = self.list.pop(0)

            if event is not None:
                event(self.zeroconf)
                

class ServiceInfo(object):
    """Service information"""
    
    def __init__(self, type, name, address=None, port=None, weight=0, priority=0, properties=None, server=None):
        """Create a service description.

        type: fully qualified service type name
        name: fully qualified service name
        address: IP address as unsigned short, network byte order
        port: port that the service runs on
        weight: weight of the service
        priority: priority of the service
        properties: dictionary of properties (or a string holding the bytes for the text field)
        server: fully qualified name for service host (defaults to name)"""

        if not name.endswith(type):
            raise BadTypeInNameException
        self.type = type
        self.name = name
        self.address = address
        self.port = port
        self.weight = weight
        self.priority = priority
        if server:
            self.server = server
        else:
            self.server = name
        self.setProperties(properties)

    def setProperties(self, properties):
        """Sets properties and text of this info from a dictionary"""
        if isinstance(properties, dict):
            self.properties = properties
            list = []
            result = ''
            for key in properties:
                value = properties[key]
                if value is None:
                    suffix = ''.encode('utf-8')
                elif isinstance(value, str):
                    suffix = value.encode('utf-8')
                elif isinstance(value, int):
                    if value:
                        suffix = 'true'
                    else:
                        suffix = 'false'
                else:
                    suffix = ''.encode('utf-8')
                list.append('='.join((key, suffix)))
            for item in list:
                result = ''.join((result, struct.pack('!c', chr(len(item))), item))
            self.text = result
        else:
            self.text = properties

    def setText(self, text):
        """Sets properties and text given a text field"""
        self.text = text
        try:
            result = {}
            end = len(text)
            index = 0
            strs = []
            while index < end:
                length = ord(text[index])
                index += 1
                strs.append(text[index:index+length])
                index += length
            
            for s in strs:
                eindex = s.find('=')
                if eindex == -1:
                    # No equals sign at all
                    key = s
                    value = 0
                else:
                    key = s[:eindex]
                    value = s[eindex+1:]
                    if value == 'true':
                        value = 1
                    elif value == 'false' or not value:
                        value = 0

                # Only update non-existent properties
                if key and result.get(key) == None:
                    result[key] = value

            self.properties = result
        except:
            traceback.print_exc()
            self.properties = None
            
    def getType(self):
        """Type accessor"""
        return self.type

    def getName(self):
        """Name accessor"""
        if self.type is not None and self.name.endswith("." + self.type):
            return self.name[:len(self.name) - len(self.type) - 1]
        return self.name

    def getAddress(self):
        """Address accessor"""
        return self.address

    def getPort(self):
        """Port accessor"""
        return self.port

    def getPriority(self):
        """Pirority accessor"""
        return self.priority

    def getWeight(self):
        """Weight accessor"""
        return self.weight

    def getProperties(self):
        """Properties accessor"""
        return self.properties

    def getText(self):
        """Text accessor"""
        return self.text

    def getServer(self):
        """Server accessor"""
        return self.server

    def updateRecord(self, zeroconf, now, record):
        """Updates service information from a DNS record"""
        if record is not None and not record.isExpired(now):
            if record.type == _TYPE_A:
                if record.name == self.name:
                    self.address = record.address
            elif record.type == _TYPE_SRV:
                if record.name == self.name:
                    self.server = record.server
                    self.port = record.port
                    self.weight = record.weight
                    self.priority = record.priority
                    self.address = None
                    self.updateRecord(zeroconf, now, zeroconf.cache.getByDetails(self.server, _TYPE_A, _CLASS_IN))
            elif record.type == _TYPE_TXT:
                if record.name == self.name:
                    self.setText(record.text)

    def request(self, zeroconf, timeout):
        """Returns true if the service could be discovered on the
        network, and updates this object with details discovered.
        """
        now = currentTimeMillis()
        delay = _LISTENER_TIME
        next = now + delay
        last = now + timeout
        result = 0
        try:
            zeroconf.addListener(self, DNSQuestion(self.name, _TYPE_ANY, _CLASS_IN))
            while self.server is None or self.address is None or self.text is None:
                if last <= now:
                    return 0
                if next <= now:
                    out = DNSOutgoing(_FLAGS_QR_QUERY)
                    out.addQuestion(DNSQuestion(self.name, _TYPE_SRV, _CLASS_IN))
                    out.addAnswerAtTime(zeroconf.cache.getByDetails(self.name, _TYPE_SRV, _CLASS_IN), now)
                    out.addQuestion(DNSQuestion(self.name, _TYPE_TXT, _CLASS_IN))
                    out.addAnswerAtTime(zeroconf.cache.getByDetails(self.name, _TYPE_TXT, _CLASS_IN), now)
                    if self.server is not None:
                        out.addQuestion(DNSQuestion(self.server, _TYPE_A, _CLASS_IN))
                        out.addAnswerAtTime(zeroconf.cache.getByDetails(self.server, _TYPE_A, _CLASS_IN), now)
                    zeroconf.send(out)
                    next = now + delay
                    delay = delay * 2

                zeroconf.wait(min(next, last) - now)
                now = currentTimeMillis()
            result = 1
        finally:
            zeroconf.removeListener(self)
            
        return result

    def __eq__(self, other):
        """Tests equality of service name"""
        if isinstance(other, ServiceInfo):
            return other.name == self.name
        return 0

    def __ne__(self, other):
        """Non-equality test"""
        return not self.__eq__(other)

    def __repr__(self):
        """String representation"""
        result = "service[%s,%s:%s," % (self.name, socket.inet_ntoa(self.getAddress()), self.port)
        if self.text is None:
            result += "None"
        else:
            if len(self.text) < 20:
                result += self.text
            else:
                result += self.text[:17] + "..."
        result += "]"
        return result
                

class Zeroconf(object):
    """Implementation of Zeroconf Multicast DNS Service Discovery

    Supports registration, unregistration, queries and browsing.
    """
    def __init__(self, bindaddress=None):
        """Creates an instance of the Zeroconf class, establishing
        multicast communications, listening and reaping threads."""
        globals()['_GLOBAL_DONE'] = 0
        if bindaddress is None:
            self.intf = socket.gethostbyname(socket.gethostname())
        else:
            self.intf = bindaddress
        self.group = ('', _MDNS_PORT)
        self.socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
        try:
            self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
            self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
        except:
            # SO_REUSEADDR should be equivalent to SO_REUSEPORT for
            # multicast UDP sockets (p 731, "TCP/IP Illustrated,
            # Volume 2"), but some BSD-derived systems require
            # SO_REUSEPORT to be specified explicity.  Also, not all
            # versions of Python have SO_REUSEPORT available.  So
            # if you're on a BSD-based system, and haven't upgraded
            # to Python 2.3 yet, you may find this library doesn't
            # work as expected.
            #
            pass
        self.socket.setsockopt(socket.SOL_IP, socket.IP_MULTICAST_TTL, 255)
        self.socket.setsockopt(socket.SOL_IP, socket.IP_MULTICAST_LOOP, 1)
        try:
            self.socket.bind(self.group)
        except:
            # Some versions of linux raise an exception even though
            # the SO_REUSE* options have been set, so ignore it
            #
            pass
        self.socket.setsockopt(socket.SOL_IP, socket.IP_MULTICAST_IF, socket.inet_aton(self.intf) + socket.inet_aton('0.0.0.0'))
        self.socket.setsockopt(socket.SOL_IP, socket.IP_ADD_MEMBERSHIP, socket.inet_aton(_MDNS_ADDR) + socket.inet_aton('0.0.0.0'))

        self.listeners = []
        self.browsers = []
        self.services = {}

        self.cache = DNSCache()

        self.condition = threading.Condition()
        
        self.engine = Engine(self)
        self.listener = Listener(self)
        self.reaper = Reaper(self)

    def isLoopback(self):
        return self.intf.startswith("127.0.0.1")

    def isLinklocal(self):
        return self.intf.startswith("169.254.")

    def wait(self, timeout):
        """Calling thread waits for a given number of milliseconds or
        until notified."""
        self.condition.acquire()
        self.condition.wait(timeout/1000)
        self.condition.release()

    def notifyAll(self):
        """Notifies all waiting threads"""
        self.condition.acquire()
        self.condition.notifyAll()
        self.condition.release()

    def getServiceInfo(self, type, name, timeout=3000):
        """Returns network's service information for a particular
        name and type, or None if no service matches by the timeout,
        which defaults to 3 seconds."""
        info = ServiceInfo(type, name)
        if info.request(self, timeout):
            return info
        return None

    def addServiceListener(self, type, listener):
        """Adds a listener for a particular service type.  This object
        will then have its updateRecord method called when information
        arrives for that type."""
        self.removeServiceListener(listener)
        self.browsers.append(ServiceBrowser(self, type, listener))

    def removeServiceListener(self, listener):
        """Removes a listener from the set that is currently listening."""
        for browser in self.browsers:
            if browser.listener == listener:
                browser.cancel()
                del(browser)

    def registerService(self, info, ttl=_DNS_TTL):
        """Registers service information to the network with a default TTL
        of 60 seconds.  Zeroconf will then respond to requests for
        information for that service.  The name of the service may be
        changed if needed to make it unique on the network."""
        self.checkService(info)
        self.services[info.name.lower()] = info
        now = currentTimeMillis()
        nextTime = now
        i = 0
        while i < 3:
            if now < nextTime:
                self.wait(nextTime - now)
                now = currentTimeMillis()
                continue
            out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA)
            out.addAnswerAtTime(DNSPointer(info.type, _TYPE_PTR, _CLASS_IN, ttl, info.name), 0)
            out.addAnswerAtTime(DNSService(info.name, _TYPE_SRV, _CLASS_IN, ttl, info.priority, info.weight, info.port, info.server), 0)
            out.addAnswerAtTime(DNSText(info.name, _TYPE_TXT, _CLASS_IN, ttl, info.text), 0)
            if info.address:
                out.addAnswerAtTime(DNSAddress(info.server, _TYPE_A, _CLASS_IN, ttl, info.address), 0)
            self.send(out)
            i += 1
            nextTime += _REGISTER_TIME

    def unregisterService(self, info):
        """Unregister a service."""
        try:
            del(self.services[info.name.lower()])
        except:
            pass
        now = currentTimeMillis()
        nextTime = now
        i = 0
        while i < 3:
            if now < nextTime:
                self.wait(nextTime - now)
                now = currentTimeMillis()
                continue
            out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA)
            out.addAnswerAtTime(DNSPointer(info.type, _TYPE_PTR, _CLASS_IN, 0, info.name), 0)
            out.addAnswerAtTime(DNSService(info.name, _TYPE_SRV, _CLASS_IN, 0, info.priority, info.weight, info.port, info.name), 0)
            out.addAnswerAtTime(DNSText(info.name, _TYPE_TXT, _CLASS_IN, 0, info.text), 0)
            if info.address:
                out.addAnswerAtTime(DNSAddress(info.server, _TYPE_A, _CLASS_IN, 0, info.address), 0)
            self.send(out)
            i += 1
            nextTime += _UNREGISTER_TIME

    def unregisterAllServices(self):
        """Unregister all registered services."""
        if len(self.services) > 0:
            now = currentTimeMillis()
            nextTime = now
            i = 0
            while i < 3:
                if now < nextTime:
                    self.wait(nextTime - now)
                    now = currentTimeMillis()
                    continue
                out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA)
                for info in self.services.values():
                    out.addAnswerAtTime(DNSPointer(info.type, _TYPE_PTR, _CLASS_IN, 0, info.name), 0)
                    out.addAnswerAtTime(DNSService(info.name, _TYPE_SRV, _CLASS_IN, 0, info.priority, info.weight, info.port, info.server), 0)
                    out.addAnswerAtTime(DNSText(info.name, _TYPE_TXT, _CLASS_IN, 0, info.text), 0)
                    if info.address:
                        out.addAnswerAtTime(DNSAddress(info.server, _TYPE_A, _CLASS_IN, 0, info.address), 0)
                self.send(out)
                i += 1
                nextTime += _UNREGISTER_TIME

    def checkService(self, info):
        """Checks the network for a unique service name, modifying the
        ServiceInfo passed in if it is not unique."""
        now = currentTimeMillis()
        nextTime = now
        i = 0
        while i < 3:
            for record in self.cache.entriesWithName(info.type):
                if record.type == _TYPE_PTR and not record.isExpired(now) and record.alias == info.name:
                    if (info.name.find('.') < 0):
                        info.name = info.name + ".[" + info.address + ":" + info.port + "]." + info.type
                        self.checkService(info)
                        return
                    raise NonUniqueNameException
            if now < nextTime:
                self.wait(nextTime - now)
                now = currentTimeMillis()
                continue
            out = DNSOutgoing(_FLAGS_QR_QUERY | _FLAGS_AA)
            self.debug = out
            out.addQuestion(DNSQuestion(info.type, _TYPE_PTR, _CLASS_IN))
            out.addAuthorativeAnswer(DNSPointer(info.type, _TYPE_PTR, _CLASS_IN, _DNS_TTL, info.name))
            self.send(out)
            i += 1
            nextTime += _CHECK_TIME

    def addListener(self, listener, question):
        """Adds a listener for a given question.  The listener will have
        its updateRecord method called when information is available to
        answer the question."""
        now = currentTimeMillis()
        self.listeners.append(listener)
        if question is not None:
            for record in self.cache.entriesWithName(question.name):
                if question.answeredBy(record) and not record.isExpired(now):
                    listener.updateRecord(self, now, record)
        self.notifyAll()

    def removeListener(self, listener):
        """Removes a listener."""
        try:
            self.listeners.remove(listener)
            self.notifyAll()
        except:
            pass

    def updateRecord(self, now, rec):
        """Used to notify listeners of new information that has updated
        a record."""
        for listener in self.listeners:
            listener.updateRecord(self, now, rec)
        self.notifyAll()

    def handleResponse(self, msg):
        """Deal with incoming response packets.  All answers
        are held in the cache, and listeners are notified."""
        now = currentTimeMillis()
        for record in msg.answers:
            expired = record.isExpired(now)
            if record in self.cache.entries():
                if expired:
                    self.cache.remove(record)
                else:
                    entry = self.cache.get(record)
                    if entry is not None:
                        entry.resetTTL(record)
                        record = entry
            else:
                self.cache.add(record)
                
            self.updateRecord(now, record)

    def handleQuery(self, msg, addr, port):
        """Deal with incoming query packets.  Provides a response if
        possible."""
        out = None

        # Support unicast client responses
        #
        if port != _MDNS_PORT:
            out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA, 0)
            for question in msg.questions:
                out.addQuestion(question)
        
        for question in msg.questions:
            if question.type == _TYPE_PTR:
                for service in self.services.values():
                    if question.name == service.type:
                        if out is None:
                            out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA)
                        out.addAnswer(msg, DNSPointer(service.type, _TYPE_PTR, _CLASS_IN, _DNS_TTL, service.name))
            else:
                try:
                    if out is None:
                        out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA)
                    
                    # Answer A record queries for any service addresses we know
                    if question.type == _TYPE_A or question.type == _TYPE_ANY:
                        for service in self.services.values():
                            if service.server == question.name.lower():
                                out.addAnswer(msg, DNSAddress(question.name, _TYPE_A, _CLASS_IN | _CLASS_UNIQUE, _DNS_TTL, service.address))
                    
                    service = self.services.get(question.name.lower(), None)
                    if not service: continue
                    
                    if question.type == _TYPE_SRV or question.type == _TYPE_ANY:
                        out.addAnswer(msg, DNSService(question.name, _TYPE_SRV, _CLASS_IN | _CLASS_UNIQUE, _DNS_TTL, service.priority, service.weight, service.port, service.server))
                    if question.type == _TYPE_TXT or question.type == _TYPE_ANY:
                        out.addAnswer(msg, DNSText(question.name, _TYPE_TXT, _CLASS_IN | _CLASS_UNIQUE, _DNS_TTL, service.text))
                    if question.type == _TYPE_SRV:
                        out.addAdditionalAnswer(DNSAddress(service.server, _TYPE_A, _CLASS_IN | _CLASS_UNIQUE, _DNS_TTL, service.address))
                except:
                    traceback.print_exc()
                
        if out is not None and out.answers:
            out.id = msg.id
            self.send(out, addr, port)

    def send(self, out, addr = _MDNS_ADDR, port = _MDNS_PORT):
        """Sends an outgoing packet."""
        # This is a quick test to see if we can parse the packets we generate
        #temp = DNSIncoming(out.packet())
        try:
            bytes_sent = self.socket.sendto(out.packet(), 0, (addr, port))
        except:
            # Ignore this, it may be a temporary loss of network connection
            pass

    def close(self):
        """Ends the background threads, and prevent this instance from
        servicing further queries."""
        if globals()['_GLOBAL_DONE'] == 0:
            globals()['_GLOBAL_DONE'] = 1
            self.notifyAll()
            self.engine.notify()
            self.unregisterAllServices()
            self.socket.setsockopt(socket.SOL_IP, socket.IP_DROP_MEMBERSHIP, socket.inet_aton(_MDNS_ADDR) + socket.inet_aton('0.0.0.0'))
            self.socket.close()
            
# Test a few module features, including service registration, service
# query (for Zoe), and service unregistration.

if __name__ == '__main__':    
    print "Multicast DNS Service Discovery for Python, version", __version__
    r = Zeroconf()
    print "1. Testing registration of a service..."
    desc = {'version':'0.10','a':'test value', 'b':'another value'}
    info = ServiceInfo("_http._tcp.local.", "My Service Name._http._tcp.local.", socket.inet_aton("127.0.0.1"), 1234, 0, 0, desc)
    print "   Registering service..."
    r.registerService(info)
    print "   Registration done."
    print "2. Testing query of service information..."
    print "   Getting ZOE service:", str(r.getServiceInfo("_http._tcp.local.", "ZOE._http._tcp.local."))
    print "   Query done."
    print "3. Testing query of own service..."
    print "   Getting self:", str(r.getServiceInfo("_http._tcp.local.", "My Service Name._http._tcp.local."))
    print "   Query done."
    print "4. Testing unregister of service information..."
    r.unregisterService(info)
    print "   Unregister done."
    r.close()