All DatabasesInside Mac - DAM/Ed/PPC/Slot
session
Ports, Sessions, and Message Blocks
To initiate communication between applications, you must first open a port. A
port is a portal through which your application can exchange information
with another application. A port is designated by a port name and a
location name.
A port name is a unique identifier for a particular application on a computer.
The port name contains a name string, a type string, and a
script code for localization. The location name identifies the location of the
computer on the network. The location name contains an object string, a type
string, and a zone. An application can specify an alias location name by
modifying its type string.
Your application can open as many ports as it requires as long as each
port name is unique within a particular computer.
Through its port, an open application can communicate with another open
application during a session. One port can support any number of
communication sessions. During a session, an application sends and receives
data in the form of a message block. The PPC Toolbox treats each block of data
as a byte stream and delivers it in the same sequence in which it was sent.
The words port name, location name, session, and message block are
programmatic terms. You should not use them in the user interface of your
application or in your user documentation. Instead, refer to a file that contains
executable code as an application program. An application program that opens
and uses PPC ports supports program linking. When you link two application
programs together, you are forming a program link. A link allows two
application programs to communicate with each other-you unlink two
application programs when you break the link between them. You can compare
the link between two application programs to the communication established
using telephones. For example, a program link is similar to a telephone
connection that enables various forms of communication such as
human-to-human, modem-to-modem, and facsimile machine-to-facsimile
machine.
The following figure shows a database application on one computer that has
initiated a session with a spreadsheet application located on another computer
on the network.
A PPC Toolbox session between two applications
The database application's port name consists of "store data" (the name
string) and " database" (the type string). Its location name consists of "Jane
Doe's Macintosh" (the object string), "PPCToolBox" (the type string), and
"twilight" (the AppleTalk zone).
The spreadsheet application's port name consists of "display data" (the name
string) and " spreadsheet" (the type string). Its location name consists of "Joe
Smith's Macintosh" (the object string), "PPCToolBox" (the type string), and
"loading" (the AppleTalk zone).
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