Supported File Sharing Protocols in Mac OS 9

Mac OS 9 relied on a distinct set of native networking technologies to enable file sharing across local networks and the early consumer internet. Central to this architecture was the Apple Filing Protocol (AFP), which operated across both legacy AppleTalk stacks and modern TCP/IP connections. Additionally, updates to Mac OS 9 incorporated nascent web-based protocols like WebDAV to facilitate remote cloud storage. This article details the specific file sharing protocols natively supported in Mac OS 9, their operational mechanisms, and third-party extensions of the era.

Apple Filing Protocol (AFP)

The Apple Filing Protocol was the core, native file sharing standard in Mac OS 9. The operating system primarily shipped with support for AFP versions 2.1 and 2.2. AFP preserved classic Mac OS file system nuances that foreign protocols could not, such as resource forks, file type and creator codes, custom folder icons, and Mac-specific metadata. In Mac OS 9, the built-in "File Sharing" control panel allowed any machine to function simultaneously as an AFP client and a lightweight AFP server for up to ten concurrent guests.

AFP over AppleTalk

Traditionally, AFP ran strictly over Apple's proprietary AppleTalk protocol suite, utilizing the Datagram Delivery Protocol (DDP) and AppleTalk Session Protocol (ASP). In Mac OS 9, AFP over AppleTalk remained fully supported to maintain backward compatibility with older Macintosh hardware, System 7, and Mac OS 8 systems. It offered zero-configuration local networking, allowing users to locate available servers dynamically through the classic Chooser utility without needing to configure IP addresses or subnet masks.

AFP over TCP/IP

To adapt to the dominance of Ethernet and internet-standard networking, Mac OS 9 fully integrated AFP over TCP/IP via port 548. Operating over the AppleTalk Data Stream Protocol (ADSP) encapsulated in TCP packets, this configuration allowed Mac OS 9 users to connect to local and remote AFP servers using standard IP addresses or DNS domain names. Users accessed this via the "Network Browser" or by pressing Command-K in the Chooser to enter an IP address manually. AFP over TCP/IP provided substantially higher transfer speeds compared to traditional AppleTalk routing.

WebDAV (HTTP Extensions for Distributed Authoring)

Starting with Mac OS 9.1, Apple introduced native support for WebDAV (Web Distributed Authoring and Versioning). This protocol runs over standard HTTP (port 80) or HTTPS (port 443) and was incorporated primarily to power Apple’s iTools service—specifically the "iDisk" virtual storage drive. WebDAV allowed Mac OS 9 to mount remote internet directories directly onto the desktop as native volumes, bypassing firewall restrictions commonly associated with AppleTalk and non-standard ports.

While not a traditional file-mounting protocol, Mac OS 9 included a built-in feature called Personal Web Sharing. This service utilized standard Hypertext Transfer Protocol (HTTP) to turn a user's designated "Web Pages" folder into a locally hosted website. Other users on the local network or internet could access and download shared files using any standard web browser, without requiring an AFP client.

Non-Native Protocols: SMB/CIFS and NFS

Mac OS 9 did not natively support Windows-standard SMB/CIFS (Server Message Block) or Unix-standard NFS (Network File System). To share files with Windows or Unix environments via their native protocols, users had to install third-party software extensions:

Thursby Software’s DAVE: Added full NetBIOS and SMB/CIFS client and server capabilities to Mac OS 9, allowing Macs to integrate into Windows Workgroups and NT domains.
Connectix DoubleTalk: Provided an alternative client-side SMB implementation for accessing Windows shared folders.
MacNFS: Enabled access to Unix and Linux NFS exports from within the Mac OS 9 Finder.

Native integration of SMB and NFS would not arrive until the transition to Mac OS X.