diff -r 31dade089db5 -r ae63ccc29444 util/Zeroconf.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/util/Zeroconf.py	Wed May 09 00:12:40 2012 +0200
@@ -0,0 +1,1559 @@
+""" 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, int(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.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.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.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.server:
+                    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.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
+        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
+
+        if self.intf is not None:
+            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):
+        if self.intf is not None:
+            return self.intf.startswith("127.0.0.1")
+        return False
+
+    def isLinklocal(self):
+        if self.intf is not None:
+            return self.intf.startswith("169.254.")
+        return False
+
+    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()