When the Mac was developed in the early 1980s, an easy-to-use networking protocol called AppleTalk allowed multiple users to share files and devices, such as printers and scanners. AppleTalk went through several changes, including the ability to route AppleTalk packets between networks (called Zones in AppleTalk parlance) and run AppleTalk over Ethernet. Because AppleTalk has been around since the introduction of the Mac, large numbers of networks still support AppleTalk, and many AppleTalk-only devices still exist.

Mac OS X continues to support AppleTalk even though IP is its primary networking protocol. When you have an Ethernet or AirPort connection, AppleTalk is automatically running by default so any available AppleTalk devices on the network can be used. You can control whether AppleTalk is active for a network connection by using the Network preference panel.

From the command line, you can check the status of AppleTalk on your machine by running the appletalk -s command, as shown in Example 11-8.

$ appletalk -s
AppleTalk interface.............. en1
Network Number .................. 65420 (0xff8c)
Node ID ......................... 122 (0x7a)
Current Zone .................... *
Bridge net ...................... 0 (0x0)
Bridge number ................... 0 (0x0)
DDP statistics:
Packets Transmitted ............. 64
Bytes Transmitted ............... 2751
Best Router Cache used (pkts) ... 0
Packets Received ................ 79
Bytes Received .................. 3644
Packets for unregistered socket . 0
Packets for out of range socket . 2
Length errors ................... 0
Checksum errors ................. 0
Packets dropped (no buffers) .... 0

The output from appletalk -s shows the network interface AppleTalk is active on, the numeric network and node identifiers, and some statistics about the packets being transmitted via AppleTalk.

You can see the AppleTalk hosts and services on the network by using the atlookup command, as shown in Example 11-9.

$ atlookup
Found 3 entries in zone *
ff8c.7a.80 Ronin:Darwin
ff8c.7a.80 Ronin:AFPServer
ffee.44.80 Hobbes:Darwin
ffee.44.81 Hobbes:AFPServer

The first column in the output is composed of three dot-separated hexadecimal numbers. The first two numbers identify the host’s network number and ID. The third number identifies the service being provided. The second column is composed of the name of the host as well as the name of the service being provided. In Example 11-9, the first two lines indicate that there is a Darwin-based (Mac OS X) machine on the network named Ronin and that its Apple Filing Protocol (AFP) service is running. The next two lines describe the same for the host Hobbes.