ShareWay IP Gateway User's Guide

How ShareWay IP Works

File Sharing

The ShareWay IP Gateway only implements a very small part of the AppleTalk Filing Protocol (AFP). For the most part, ShareWay IP simply translates the underlying AppleTalk protocols used by most AFP servers into TCP/IP, the protocols used on the Internet. In technical terms, the gateway translates ASP (AppleTalk Session Protocol) over AppleTalk to Apple's Data Stream Interface (DSI) over TCP/IP and vice versa. See Figure 1 below. DSI was introduced with AppleShare IP 5.0. For more information on DSI, refer to AFP 2.2 Specification, Apple Computer.

Like AppleShare IP, ShareWay IP uses TCP port number 548 to communicate with the AppleShare Client. If your network has a firewall between ShareWay IP and the Internet, and you wish ShareWay IP to be accessible from the Internet, remember to allow access to port 548 through that firewall. If you need ShareWay IP to run a port other than 548, you must purchase the ShareWay IP Professional Edition.

Figure 1. How ShareWay IP works

If ShareWay IP and the server are on the same Macintosh, the indicated communication between ShareWay IP and the server over AppleTalk is internal to the machine on which they are installed. This is always the case with ShareWay IP Personal.

In addition to translating between AppleTalk and TCP/IP protocols, ShareWay IP also mimics other aspects of AFP servers. For instance, if it detects a loss of connectivity with either the client or the server, ShareWay IP will wait two minutes before terminating the session with the other end.

SLP Registration

Service Location Protocol (SLP) is an Internet-standard protocol which enables network services to make themselves known so they can be found dynamically on a TCP/IP network. It is similar in concept to servers registering with AppleTalk and the Chooser being able to locate them. SLP is implemented in Mac OS 8.5 as the SLP plug-in, located in the System's Extensions folder.

Running on Mac OS 8.5, ShareWay IP 2.0 registers with the Mac OS using SLP. In particular, ShareWay registers a URL of the form:

afp://IP-address/?NAME=TargetMachineName&ZONE=ZoneName

IP-address is the IP address of the ShareWay IP machine

TargetMachineName is the target server's machine name

ZoneName (optional) is the name of the zone (if zones are present) in which the target server resides

Registration is automatic, and transparent to the user. ShareWay IP deregisters when the Gateway or targeted server is stopped or the ShareWay application is quit. Registered URLs are used by Open Door's AFP Engage! 2.0 to dynamically find, display and initiate access to ShareWay-targeted servers, using a simple point-and-click interface. To prevent the ShareWay IP server from showing up in AFP Engage's Browse window, simply disable the SLP plug-in on that ShareWay IP's machine, using the Extensions Manager Control Panel.

For more information on the Service Location Protocol, see Open Door's white paper on the subject.

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