ipc between different users
lazarus / 38-Networking and Web Programming

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tintinux · 2025-08-30 08:30

Hi

Using  Linux Ubuntu 24.04 and Lazarus 4.2.0

I compile and run  simpleipcserver (server) and checkipcserver
(client) taken without change from the examples provided in the
distribution.

It works fine when both are launched by the same user.
When the server is launched by an user different of the the client, it
is not found  by the client ("Server is NOT runnning").

The property Global is set to TRUE in the server source.
It is written in https://wiki.freepascal.org/SimpleIPC : On multiuser
systems, eg, Unix systems, in Global Mode, note that the pipe that IPC
creates must have a distinctive name between individual users. Doesn't
it suggest that it should work system wide, between different users ?

Is there something to add, to make it work ?  Or isn't it possible ?

Thanks

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tintinux · 2025-08-30 09:18

The strange thing is that in the sources (simpleipc.pp)  the property
Global (or the variable FGlobal) are never used...

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n7800 · 2025-08-31 09:26

Quote from: tintinux on August 30, 2025, 11:18:59 amThe strange thing
is that in the sources (simpleipc.pp)  the property Global (or the
variable FGlobal) are never used...

If you right-click and select "Find > Find Identifier References" you
can find one usage. Judging by the file, it's only used on Windows.

Quote from: tintinux on August 30, 2025, 10:30:54 amIt is written in
https://wiki.freepascal.org/SimpleIPC : On multiuser systems, eg, Unix
systems, in Global Mode, note that the pipe that IPC creates must have
a distinctive name between individual users. Doesn't it suggest that
it should work system wide, between different users ?

Is there something to add, to make it work ?  Or isn't it possible ?

I think I see an open issue on the compiler bug tracker about this.

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dbannon · 2025-08-31 12:55

I think if you want to have IPC between concurrent users, DBus is
probably the approved way to do so. At least on Linux ....

Davo

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Thaddy · 2025-08-31 14:13

Correct. I would also use dBus here.
At good introductary article - for intermediate programmers - is still
Michael van Canneyt's
https://www.freepascal.org/~michael/articles/dbus2/dbus2.pdf
Also has the sourcecode here:
https://www.freepascal.org/~michael/articles/dbus2/dbus-code.zip

It is 15 years old but still good for the current FPC.

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tintinux · 2025-09-01 06:01

Thanks for your answers.

I tried with IPC and it works not too bad for my needs.
Provided there is no need to exchange between different users (or
machines of course).

DBus looks is much more complex and the article says it requires a
daemon.
There is not much information about this daemon, but if a permanent
service is required, it is a nogo for me.

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Thaddy · 2025-09-01 06:19

dbus is part of most linux desktop environments nowadays, its daemon
is  likely always running.