What is Apple's Bonjour?

Apple has implemented a corresponding technology so that Apple devices and network devices compatible with them can recognize and work with one another without further configuration. This technology, called "Bonjour", enables Zero Configuration Networking (Zeroconf) and, as an open source solution, includes services such as Multicast DNS (mDNS), DNS-SD and IPv4LL. Bonjour is the user-initiated successor to AppleTalk and was called Rendezvous at the beginning of the implementation. In addition to macOS, iOS, tvOS and other Apple systems, the technology is also available for Windows. The most common use case for Bonjour is simply connecting and using network printers.

The history of Bonjour as an Apple service

In 1983, Apple bundled several network protocols under the AppleTalk name to make it easy to connect multiple Apple computers on a network. The individual computers could thus access common resources, printers and the like without major technical effort. PCs could be included in appropriate networks using LocalTalk.

AppleTalk was launched with the Introduction of "Mac OS X" systems UNIX-based dropped in 2001, which displeased many users on Mac networks. Because network configurations had to be made again via IP address. The frequently used printer example was a focus of user frustration.

If you read the history of the Bonjour service, you will quickly find the name Stuart Cheshire in this context. This is said to have first exchanged views on the subject in an e-mail discussion group and later to have initiated ideas for an AppleTalk successor. He wanted simple network tasks to be possible without an administrator.

After a while, Apple simply hired Stuart Cheshire and put the development of an AppleTalk successor in his hands. Rendezvous was created as a Zeroconf solution, which was later renamed Bonjour due to trademark disputes. The Bonjour technology is open source and can also be used for Windows. 

What is Bonjour doing as a Zeroconf service?

As the term "Zero Configuration Networking" suggests, Bonjour and similar technologies are intended to ensure that network devices recognize and work together without major user-side measures (without configuration). Setting up connections, assigning access rights and much more should therefore be standardized and run automatically. The following tasks are taken on:

• Assign individual IP addresses without a DHCP server
• Resolving hostnames and IPs without a DNS server
• List existing devices and services without a directory server

Important abbreviations of Bonjour protocols

The network service bundles various protocols for the detection and communication of devices and apps. A corresponding insight can be helpful for the general understanding as well as for developers. So here are the individual protocol specifications:

• IPv4LL - Dynamically configure IPv4 link-local addresses
• mDNS – Multicast DNS
• DNS-SD - DNS-based service discovery
• DNS-LLQ – Long-lived DNS Queries
• DNS-UL - Dynamic DNS update leases
• NAT-PMP – NAT Port Mapping Protocol

Which Apple devices and programs use Bonjour?

Bonjour was primarily developed for the Mac, but is now used on pretty much all other Apple devices. The iPhone, iPad, Apple TV and many other devices use Bonjour to discover and interact with each other on a (wireless) network.

Apps such as Safari and iTunes or Music continue to use the service. The latter can, for example, recognize devices with shared music libraries in order to access them. About AirPrint enables a wireless printer connection – see also AirPrint printer. And Adobe apps also use Bonjour on hardware that is network-capable. Hardware and software that works with Bonjour can be addressed via a Windows version of the service via PC.

Bonjour resources for developers and interested parties

With this post I just wanted to give you a little insight into the topic. If you are interested in Bonjour and even implementing it in your apps or hardware, there are much more detailed sources. For example, Apple offers B. Extensive guides and developer resources to help. Here is a small selection:

• Bonjour code, license notes and more: developer website
• Apple Platforms Implementation Guide: Complete manual
• Apple Open Source Resources: Complete overview

Johannes Domke

After graduating from high school, Johannes completed an apprenticeship as a business assistant specializing in foreign languages. But then he decided to research and write, which resulted in his independence. For several years he has been working for Sir Apfelot, among others. His articles include product introductions, news, manuals, video games, consoles, and more. He follows Apple keynotes live via stream.