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Pure Python Multicast DNS Service Discovery Library (Bonjour/Avahi compatible)

Project description



This is fork of pyzeroconf, Multicast DNS Service Discovery for Python, originally by Paul Scott-Murphy (, modified by William McBrine (

The original William McBrine’s fork note:

This fork is used in all of my TiVo-related projects: HME for Python
(and therefore HME/VLC), Network Remote, Remote Proxy, and pyTivo.
Before this, I was tracking the changes for in three
separate repos. I figured I should have an authoritative source.

Although I make changes based on my experience with TiVos, I expect that
they're generally applicable. This version also includes patches found
on the now-defunct (?) Launchpad repo of pyzeroconf, and elsewhere
around the net -- not always well-documented, sorry.

Compatible with:

  • Bonjour
  • Avahi

Compared to some other Zeroconf/Bonjour/Avahi Python packages, python-zeroconf:

  • isn’t tied to Bonjour or Avahi
  • doesn’t use D-Bus
  • doesn’t force you to use particular event loop or Twisted
  • is pip-installable
  • has PyPI distribution

Python compatibility

  • CPython 3.6+
  • PyPy3 5.8+


This project’s versions follow the following pattern: MAJOR.MINOR.PATCH.

  • MAJOR version has been 0 so far
  • MINOR version is incremented on backward incompatible changes
  • PATCH version is incremented on backward compatible changes


There are some people using this package. I don’t actively use it and as such any help I can offer with regard to any issues is very limited.

IPv6 support

IPv6 support is relatively new and currently limited, specifically:

  • InterfaceChoice.All is an alias for InterfaceChoice.Default on non-POSIX systems.
  • On Windows specific interfaces can only be requested as interface indexes, not as IP addresses.
  • Dual-stack IPv6 sockets are used, which may not be supported everywhere (some BSD variants do not have them).
  • Listening on localhost (::1) does not work. Help with understanding why is appreciated.

How to get python-zeroconf?

The easiest way to install python-zeroconf is using pip:

pip install zeroconf

How do I use it?

Here’s an example of browsing for a service:

from zeroconf import ServiceBrowser, Zeroconf

class MyListener:

    def remove_service(self, zeroconf, type, name):
        print("Service %s removed" % (name,))

    def add_service(self, zeroconf, type, name):
        info = zeroconf.get_service_info(type, name)
        print("Service %s added, service info: %s" % (name, info))

zeroconf = Zeroconf()
listener = MyListener()
browser = ServiceBrowser(zeroconf, "_http._tcp.local.", listener)
    input("Press enter to exit...\n\n")


Discovery and service registration use all available network interfaces by default. If you want to customize that you need to specify interfaces argument when constructing Zeroconf object (see the code for details).

If you don’t know the name of the service you need to browse for, try:

from zeroconf import ZeroconfServiceTypes

See examples directory for more.



  • A single socket is used for listening on responding when InterfaceChoice.Default is chosen. Thanks to J. Nick Koston.

Backwards incompatible:

  • Dropped Python 3.5 support


  • Fixed the packet generation when multiple packets are necessary, previously invalid packets were generated sometimes. Patch thanks to J. Nick Koston.


  • Fixed the IPv6 address rendering in the browser example, thanks to Alexey Vazhnov.
  • Fixed a crash happening when a service is added or removed during handle_response and improved exception handling, thanks to J. Nick Koston.


  • Loosened service name validation when receiving from the network this lets us handle some real world devices previously causing errors, thanks to J. Nick Koston.


  • Enabled ignoring duplicated messages which decreases CPU usage, thanks to J. Nick Koston.
  • Fixed spurious AttributeError: module ‘unittest’ has no attribute ‘mock’ in tests.


  • Improved cache reaper performance significantly, thanks to J. Nick Koston.
  • Added ServiceListener to __all__ as it’s part of the public API, thanks to Justin Nesselrotte.


  • Reduced a time an internal lock is held which should eliminate deadlocks in high-traffic networks, thanks to J. Nick Koston.


  • Stopped asking questions we already have answers for in cache, thanks to Paul Daumlechner.
  • Removed initial delay before querying for service info, thanks to Erik Montnemery.


  • Fixed a resource leak connected to using ServiceBrowser with multiple types, thanks to J. Nick Koston.


  • Improved Windows support when using socket errno checks, thanks to Sandy Patterson.
  • Added support for passing text addresses to ServiceInfo.
  • Improved logging (includes fixing an incorrect logging call)
  • Improved Windows compatibility by using Adapter.index from ifaddr, thanks to PhilippSelenium.
  • Improved Windows compatibility by stopping using socket.if_nameindex.
  • Fixed an OS X edge case which should also eliminate a memory leak, thanks to Emil Styrke.

Technically backwards incompatible:

  • ifaddr 0.1.7 or newer is required now.


  • Improved the logging situation (includes fixing a false-positive “packets() made no progress adding records”, thanks to Greg Badros)


  • Large multi-resource responses are now split into separate packets which fixes a bad mdns-repeater/ChromeCast Audio interaction ending with ChromeCast Audio crash (and possibly some others) and improves RFC 6762 compliance, thanks to Greg Badros
  • Added a warning presented when the listener passed to ServiceBrowser lacks update_service() callback
  • Added support for finding all services available in the browser example, thanks to Perry Kunder

Backwards incompatible:

  • Removed previously deprecated ServiceInfo address constructor parameter and property


  • Improved readability of logged incoming data, thanks to Erik Montnemery
  • Threads are given unique names now to aid debugging, thanks to Erik Montnemery
  • Fixed a regression where get_service_info() called within a listener add_service method would deadlock, timeout and incorrectly return None, fix thanks to Erik Montnemery, but Matt Saxon and Hmmbob were also involved in debugging it.


  • Added support for multiple types to ServiceBrowser, thanks to J. Nick Koston
  • Fixed a race condition where a listener gets a message before the lock is created, thanks to J. Nick Koston


  • Fixed a performance regression introduced in 0.26.0, thanks to J. Nick Koston (this is close in spirit to an optimization made in 0.24.5 by the same author)


  • Fixed a regression where service update listener wasn’t called on IP address change (it’s called on SRV/A/AAAA record changes now), thanks to Matt Saxon

Technically backwards incompatible:

  • Service update hook is no longer called on service addition (service added hook is still called), this is related to the fix above


  • Eliminated 5s hangup when calling Zeroconf.close(), thanks to Erik Montnemery


  • Reverted uniqueness assertions when browsing, they caused a regression

Backwards incompatible:

  • Rationalized handling of TXT records. Non-bytes values are converted to str and encoded to bytes using UTF-8 now, None values mean value-less attributes. When receiving TXT records no decoding is performed now, keys are always bytes and values are either bytes or None in value-less attributes.


  • Fixed issues with shared records being used where they shouldn’t be (TXT, SRV, A records are unique now), thanks to Matt Saxon
  • Stopped unnecessarily excluding host-only interfaces from InterfaceChoice.all as they don’t forbid multicast, thanks to Andreas Oberritter
  • Fixed repr() of IPv6 DNSAddress, thanks to Aldo Hoeben
  • Removed duplicate update messages sent to listeners, thanks to Matt Saxon
  • Added support for cooperating responders, thanks to Matt Saxon
  • Optimized handle_response cache check, thanks to J. Nick Koston
  • Fixed memory leak in DNSCache, thanks to J. Nick Koston


  • Fixed resetting TTL in DNSRecord.reset_ttl(), thanks to Matt Saxon
  • Improved various DNS class’ string representations, thanks to Jay Hogg


  • Fixed import-time “TypeError: ‘ellipsis’ object is not iterable.” on CPython 3.5.2


  • Added support for AWDL interface on macOS (needed and used by the opendrop project but should be useful in general), thanks to Milan Stute
  • Added missing type hints


  • Applied some significant performance optimizations, thanks to Jaime van Kessel for the patch and to Ghostkeeper for performance measurements
  • Fixed flushing outdated cache entries when incoming record is unique, thanks to Michael Hu
  • Fixed handling updates of TXT records (they’d not get recorded previously), thanks to Michael Hu


  • Added IPv6 support, thanks to Dmitry Tantsur
  • Added additional recommended records to PTR responses, thanks to Scott Mertz
  • Added handling of ENOTCONN being raised during shutdown when using Eventlet, thanks to Tamás Nepusz
  • Included the py.typed marker in the package so that type checkers know to use type hints from the source code, thanks to Dmitry Tantsur


  • Added support for MyListener call getting updates to service TXT records, thanks to Matt Saxon
  • Added support for multiple addresses when publishing a service, getting/setting single address has become deprecated. Change thanks to Dmitry Tantsur

Backwards incompatible:

  • Dropped Python 3.4 support


  • A lot of maintenance work (tooling, typing coverage and improvements, spelling) done, thanks to Ville Skyttä
  • Provided saner defaults in ServiceInfo’s constructor, thanks to Jorge Miranda
  • Fixed service removal packets not being sent on shutdown, thanks to Andrew Bonney
  • Added a way to define TTL-s through ServiceInfo contructor parameters, thanks to Andrew Bonney

Technically backwards incompatible:

  • Adjusted query intervals to match RFC 6762, thanks to Andrew Bonney
  • Made default TTL-s match RFC 6762, thanks to Andrew Bonney


  • This time really allowed incoming service names to contain underscores (patch released as part of 0.21.0 was defective)


  • Fixed import-time typing-related TypeError when older typing version is used


  • Fixed installation on Python 3.4 (we use typing now but there was no explicit dependency on it)


  • Added an error message when importing the package using unsupported Python version
  • Fixed TTL handling for published service
  • Implemented unicast support
  • Fixed WSL (Windows Subsystem for Linux) compatibility
  • Fixed occasional UnboundLocalError issue
  • Fixed UTF-8 multibyte name compression
  • Switched from netifaces to ifaddr (pure Python)
  • Allowed incoming service names to contain underscores


  • Dropped support for Python 2 (this includes PyPy) and 3.3
  • Fixed some class’ equality operators
  • ServiceBrowser entries are being refreshed when ‘stale’ now
  • Cache returns new records first now instead of last


  • Allowed installation with netifaces >= 0.10.6 (a bug that was concerning us got fixed)



  • Dropped Python 2.6 support
  • Improved error handling inside code executed when Zeroconf object is being closed


  • Better Handling of DNS Incoming Packets parsing exceptions
  • Many exceptions will now log a warning the first time they are seen
  • Catch and log sendto() errors
  • Fix/Implement duplicate name change
  • Fix overly strict name validation introduced in 0.17.6
  • Greatly improve handling of oversized packets including:
    • Implement name compression per RFC1035
    • Limit size of generated packets to 9000 bytes as per RFC6762
    • Better handle over sized incoming packets
  • Increased test coverage to 95%


  • Many improvements to address race conditions and exceptions during ZC() startup and shutdown, thanks to: morpav, veawor, justingiorgi, herczy, stephenrauch
  • Added more test coverage: strahlex, stephenrauch
  • Stephen Rauch contributed:
    • Speed up browser startup
    • Add ZeroconfServiceTypes() query class to discover all advertised service types
    • Add full validation for service names, types and subtypes
    • Fix for subtype browsing
    • Fix DNSHInfo support


  • Fixed OpenBSD compatibility, thanks to Alessio Sergi
  • Fixed race condition on ServiceBrowser startup, thanks to gbiddison
  • Fixed installation on some Python 3 systems, thanks to Per Sandström
  • Fixed “size change during iteration” bug on Python 3, thanks to gbiddison


  • Fixed support for Linux kernel versions < 3.9 (thanks to Giovanni Harting and Luckydonald, GitHub pull request #26)


  • Fixed DNSText repr on Python 3 (it’d crash when the text was longer than 10 bytes), thanks to Paulus Schoutsen for the patch, GitHub pull request #24


  • Fixed installation on Python 3.4.3+ (was failing because of enum34 dependency which fails to install on 3.4.3+, changed to depend on enum-compat instead; thanks to Michael Brennan for the original patch, GitHub pull request #22)


  • Fixed EADDRNOTAVAIL when attempting to use dummy network interfaces on Windows, thanks to daid


  • Added some Python dependencies so it’s not zero-dependencies anymore
  • Improved exception handling (it’ll be quieter now)
  • Messages are listened to and sent using all available network interfaces by default (configurable); thanks to Marcus Müller
  • Started using logging more freely
  • Fixed a bug with binary strings as property values being converted to False (; thanks to Dr. Seuss
  • Added new ServiceBrowser event handler interface (see the examples)
  • PyPy3 now officially supported
  • Fixed ServiceInfo repr on Python 3, thanks to Yordan Miladinov


  • Set up Python logging and started using it
  • Cleaned up code style (includes migrating from camel case to snake case)


  • Fixed handling closed socket (GitHub #4)


  • Forked by Jakub Stasiak
  • Made Python 3 compatible
  • Added setup script, made installable by pip and uploaded to PyPI
  • Set up Travis build
  • Reformatted the code and moved files around
  • Stopped catching BaseException in several places, that could hide errors
  • Marked threads as daemonic, they won’t keep application alive now


  • Fix for SOL_IP undefined on some systems - thanks Mike Erdely.
  • Cleaned up examples.
  • Lowercased module name.


  • Various minor changes; see git for details.
  • No longer compatible with Python 2.2. Only tested with 2.5-2.7.
  • Fork by William McBrine.


  • allow selection of binding interface
  • typo fix - Thanks A. M. Kuchlingi
  • removed all use of word ‘Rendezvous’ - this is an API change


  • 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


  • 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


  • remove all records on service unregistration
  • fix DOS security problem with readName


  • changed licensing to LGPL


  • faster shutdown on engine
  • pointer encoding of outgoing names
  • ServiceBrowser now works
  • new unit tests


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


  • ensure case insensitivty on domain names
  • support for unicast DNS queries


  • added some unit tests
  • added __ne__ adjuncts where required
  • ensure names end in ‘.local.’
  • timeout on receiving socket for clean shutdown


LGPL, see COPYING file for details.

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