Overview

To have a better understanding of Salut a Toi, this page gives a global view of what it is and what are the important concepts linked to it. You don’t need to read this to use it, but you can if you wish to understand “who is doing what”.

Salut à Toi (or SàT) is a XMPP client. XMPP is an open standard used for communication (notably instant messaging but not only). XMPP is a solid standard, which is decentralised and federated.

SàT is not only focusing on instant messaging, and aims to be a universal communication tools. In other words, you can use SàT to chat, but also to blog publicly or privately, to share file, photo albums, to create events, to have discussion forum, etc.

SàT is actually a whole ecosystem, and is made in a way that you can use it with many different interfaces (or “frontends”). There is a common central part which is called the “backend”, it handles most of the work, while frontends are mostly about the interactions with user(s).

To work, as SàT is a XMPP client, a XMPP server is needed. You can either run your own, or use an existing one (either public, or run by an organisation you belong to, like family server, run by a friend, your company, university, association, etc.). If you want to run your own server, there are already plenty of them and happily most of which are libre, you can check an up-to-date list on the XSF website (the XSF or XMPP Standards Foundation being the non-profit organisation taking care of the XMPP standard).

So to summarise, Salut à Toi, or SàT, is a communication ecosystem. Technically, it is a XMPP client which connect to an XMPP server. SàT itself works with a backend and one or many frontends.

Backend

The backend is a daemon, that means that it’s a service running in the background. It takes its main configuration from a file named sat.conf and can be in different locations (see below). It uses data in a directory called local_dir, and which default, on suitable platforms, to the corresponding XDG directory, which is most of time ~/.local/share/sat. In this directory, you’ll find the main database in the sat.db file, which is a SQLite database.

The backend is run and stopped with the sat binary. Running it without argument launch the backend in the background, with sat fg you run it in the foreground (you’ll see log directly and can stop the backend with Ctrl + c). The sat status commands help you discover if the backend is running or stopped.

Frontends

Frontends are used to make the interface between user and the backend. Frontends are adapted to different use cases, and must be started after the backend (if the backend is not started, you’ll see a message telling you so). In most installations, the backend should be started automatically when you want to use a frontend.

Bellow you’ll see a list of the official frontends currently maintained:

Cagou

Cagou is the desktop/mobile frontend. It’s probably the main interface for most users. It is based on the Kivy framework and should run of most platforms (for now it is officially tested only on GNU/Linux and Android phones and tablets).

Libervia

Libervia is the web frontend, and is the second main interface for most users. This frontend has the particularity to be in 2 parts: a server which serves HTTP content, and a client which runs in the browser. So you have Libervia server which connect to SàT backend which itself connect to the XMPP server, and your browser will connect to Libervia server.

In the browser, you can access the server in two ways: either directly with what we call Libervia pages, or with a JavaScript code in single-page application which is the Libervia client (or Libervia web app) that we have mentioned above.

The Libervia pages are web pages managing a single feature. They can work without JavaScript when it’s possible (it’s not the case for instant messaging or similar highly dynamic contents). They aims to be simple and straightforward to use.

The Libervia client is a highly dynamic web application, used to access more features. It’s more complete and may be well adapted if you want to let SàT running in a browser tab for an extended period.

Please note that the current web application (SàT 0.7) will be completely rewritten for next 0.8 release.

Last but not least, Libervia is also the central part of the new web framework of Salut à Toi. Indeed, in addition of being a frontend to SàT features (which is built with this framework), you can create totally different websites which are integrated in SàT (and so XMPP) ecosystem. This framework uses SàT template engine (based on Jinja2) and makes the creation of decentralised and federated websites simple. Thanks to this framework, it’s easy to experiment new ideas/features, or to change completely the look and feel of the Libervia frontend.

The official SàT website is made with Libervia web framework.

Primitivus

Primitivus is the Terminal User Interface (TUI). In other words, it works in console and is intended for people at ease with it. Its text only interface has several advantages: you get rid of many distracting things (like images), it works without graphical environment installed (which is often the case on servers) and it works on distant shell (like ssh) while staying gentle with your bandwidth.

Primitivus is shipped with the backend, so it should be always available once SàT is installed (but some distributions may provide it separately).

You can check Primitivus documentation for more details.

jp

Jp is the Command Line Interface (CLI). It’s a powerful tool which allows to do nearly everything you can do with other frontends. Particularly useful if you want to check something quickly, or if you want to do some automation.

You can check jp documentation documentation for more details.

Glossary

While using SàT you may see some terms or concept. This section explain the most important ones.

profile

A profile is the name linked to an account data. Usually a profile correspond to an XMPP account, but you can have several profiles using the same XMPP account (with different parameters) even if this is not usual.

On a SàT installation used by a single user, the profiles are usually used for multiple accounts. On a multi-users installations, there is usually one profile per user.

When you connect to a SàT frontend, you need to specify a profile and the associated password. The profile password is not the same as the password of the XMPP account. While this may sounds confusing, there are several reason why we use this notion of profile instead of directly the XMPP account/password:

  • SàT needs to know the plain XMPP password to connect, and it is encrypted in database. The profile password is used to encrypt/decrypt it, this way only a password hash is stored and the XMPP password is encrypted at rest.

  • As a further benefit, several passwords could be associated to the same profile (this feature is currently not used in SàT).

  • profile password can be empty, in which case no password is requested when a profile is used

    Note

    if you use an empty profile password, the XMPP password won’t be encrypted in database (or more precisely, will be trivial to decrypt).

  • a profile is a simple name associated with an account, it’s easier to remember than a whole XMPP identifier (also named “JID” for Jabber ID)

You always have a default profile which is the profile used when you don’t select any (notably used in jp). This is the first profile that you have created except if you have changed it using a frontend (you can change it with jp).

profile key

A profile key is a special name used as a way to select automatically one profile. The most important one is @DEFAULT@ which, as you can guess, means the default profile.

bridge

The “bridge” is the name used to design Salut à Toi’s IPC, or in other words the way the backend communicate with frontends. Several bridges can be used, the default one being D-Bus.

The other available bridges are:

pb
Perspective Broker is a part of Twisted (the framework used by the backend and some frontends)
embedded
this embeds the backend into the frontend. The frontend is then using the backend as a library.

SàT Media

Most of the frontends use images or other media. To avoid duplication and to make the code repositories lighter, those media are grouped in a separate repository. The SàT media repository is available at https://repos.goffi.org/sat_media. You can also download media at https://ftp.goffi.org/sat_media/sat_media.tar.bz2. The path where SàT media are installed must be specified in sat.conf in media_dir option of the [DEFAULT section.

SàT Templates

SàT embeds a Jinja2 template engine (see Libervia above). “SàT templates” refers to the default templates (i.e. the official templates, the ones used in default Libervia pages). Those template may also be used by other frontends than Libervia (jp can use them with the output arguments).

SàT templates repository is available at https://repos.goffi.org/sat_templates, they can also be downloaded at PyPI and will be installed automatically if you install Libervia.