ToolTalk User's Guide

2 An Overview of the ToolTalk Service

Contents of Chapter:
2.1 ToolTalk Architecture
2.2 Starting a ToolTalk Session
Background and Batch Sessions
X Window System
Locating ttsession
2.3 Maintaining ToolTalk Files and Databases
2.4 Demonstration Programs
As computer users increasingly demand that independently developed applications work together, inter-operability is becoming an important theme for software developers. By cooperatively using each other's facilities, inter-operating applications offer users capabilities that would be difficult to provide in a single application. The ToolTalk service is designed to facilitate the development of inter-operating applications that serve individuals and work groups.

2.1 ToolTalk Architecture

The following ToolTalk service components work together to provide inter-application communication and object information management:

The ToolTalk service uses the ONCTM Remote Procedure Call (RPC) to communicate between these ToolTalk components.

Applications provide the ToolTalk service with process and object type information. This information is stored in an XDR format file, which is referred to as the ToolTalk Types Database in this manual.

Figure 2-1 illustrates the ToolTalk service architecture.

Figure 2-1 ToolTalk Service Architecture



2.2 Starting a ToolTalk Session

The ToolTalk message server ttsession automatically starts when you open communication with the ToolTalk server. This background process must be running before any messages can be sent or received. Each message server defines a session.

Note: A session can have more than one session identifier.

To manually start a session, enter the following command on the command line:

ttsession [-a level][-d display][-spStvh][-{E|X}][-c command]
 See Table 2-1 for a description of the ttsession command line options.

Table 2-1 ttsession Command Line Options

ttsession responds to two signals.

Background and Batch Sessions

Run your application as its own session if it runs as a background job, in a batch session, or in a session bound to a character terminal. To run your application in its own session, use the -c parameter with the ttsession command, as follows:

ttsession -c [ command-to-run-in-batch ]
 This command will fork off a shell from which you can run your application.

Note: The -c parameter must be the last option on the command line; any characters placed after the -c parameter on the command line are taken as the command to be executed.

X Window System

To establish a session under the X Window System, execute ttsession either without arguments (which takes the display from the $DISPLAY environment variable) or specify the display with the -d parameter as follows:

ttsession-d :0
 When ttsession is invoked, it immediately forks and the parent copy exits; the process managing the session executes in the background. The session is registered as a property, named by _TT_SESSION on the root window of screen 0; the host and port number is given for communication with the process managing the session.

Locating ttsession

To display the sessid of the session for the Xdisplay:

xprop -root | grep _TT_SESSION

2.3 Maintaining ToolTalk Files and Databases

The ToolTalk package contains a special set of shell commands you can use to copy, move, and remove ToolTalk files (that is, files mentioned in messages and files that contain ToolTalk objects). After a standard shell command (such as cp, mv, or rm) is performed, the ToolTalk service is notified that a file location has changed.

The ToolTalk package also contains a database check and repair utility for the ToolTalk database, ttdbck, that you can use to check and repair your ToolTalk databases.

2.4 Demonstration Programs

The ToolTalk service source files contain several interesting demonstration programs:

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