FPC and DBus

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Overview

DBUS is a GNU library that implements inter-process communication. It's the default library of this kind for GNU applications. It can often be found on Linux machines.

This library provides a simple way for applications to talk to one another, using a bus sytem. These headers are the translation of the low-level C API for DBUS. In the future it is desirable that these headers be wrapped around a class to make their use easier.

Documentation

Independently from what you want to achieve, a lot of the code for a program that uses DBUS will be very similar. This is the startup and finalization code.

Startup

On startup you need to connect to the bus. Usually there is a system and a session bus. Depending on the configuration of the system, you may not have access to the system bus. Next you need to request a name on the bus. Below is some simple startup code.

var
  err: DBusError;
  conn: PDBusConnection;
  ret: cint;
begin
  { Initializes the error handling }
  dbus_error_init(@err);
 
  { Connection }
  conn := dbus_bus_get(DBUS_BUS_SESSION, @err);
 
  if dbus_error_is_set(@err) <> 0 then
  begin
    WriteLn('Connection Error: ' + err.message);
    dbus_error_free(@err);
  end;
 
  if conn = nil then Exit;
 
  { Request the name of the bus }
  ret := dbus_bus_request_name(conn, 'test.method.server', DBUS_NAME_FLAG_REPLACE_EXISTING, @err);
 
  if dbus_error_is_set(@err) <> 0 then
  begin
    WriteLn('Name Error: ' + err.message);
    dbus_error_free(@err);
  end;
 
  if ret <> DBUS_REQUEST_NAME_REPLY_PRIMARY_OWNER then Exit;
 
  ....

Shutdown

When you no longer need the bus, you should close the connection. A good place to do this in most cases is right before the application terminates.

  { Finalization }
  dbus_connection_close(conn);

Sending a Signal

Receiving a Signal

Calling a Method

Responding to Method calls

Authors

Felipe Monteiro de Carvalho


License

Status

Status: Beta

Download

Installed by default

The FPC package for DBUS resides in packages/dbus in the FPC (2.2.2+) packages tree.

You can download a full FPC repository and it will be included.

Older versions

For older versions: you can download the subversion version of this project using this command:

svn checkout http://svn.freepascal.org/svn/fpc/trunk/packages/dbus dbus

Bug Reporting

Tests are necessary to verify if all functions and structures are declared properly. Tests were done on Windows, FreeBSD and Linux operating systems. It is necessary to test if the modules work correctly in other operating system.

You can post Bug Reports to the regular bug tracker (make sure to choose the FPC project and select the Packages category)

Change Log

  • ??.??.06 DBus headers version 0.1
  1. Under construction
  • 03.11.2010 Updated DBus headers to version 1.2.16

Help

Please send help requests to the Free Pascal mailling list or on apache-modules mailing list.

See also

  • [1] - A Tutorial about using the DBUS C API