Inside Macintosh: Interapplication Communication /

Chapter 1 - Introduction to Interapplication Communication

Exchanging Message Blocks

You should be able to meet most of your application's IAC needs by using the Apple Event Manager or the Event Manager. However, if you need low-level control or services not provided by the Apple Event Manager or the Event Manager, you can use the PPC Toolbox. The PPC Toolbox lets you send large amounts of data to other applications located on the same computer or across a network. The PPC Toolbox can also be used by pieces of code that are not event-driven. The PPC Toolbox is usually called by the Operating System; device drivers, desk accessories, or other code modules can also use it.

You cannot use the PPC Toolbox to send data between applications unless both your application and the application you're communicating with are open at the same time. To initiate communication, one program opens a port and requests a session with another program. The target application must also open a port and accept the request. Once a session is established, the two programs can read and write low-level message blocks.

The PPC Toolbox also provides a standard user interface that allows a user working in one application to select another application with which to exchange data, whether the communication is achieved by means of Apple events, other high-level events, or message blocks.

The chapter "Program-to-Program Communications Toolbox" in this book describes how programs can exchange low-level message blocks.