<linkxlink:href="https://matrix.org/">Matrix</link> is an open standard for interoperable, decentralised, real-time communication over IP. It can be used to power Instant Messaging, VoIP/WebRTC signalling, Internet of Things communication - or anywhere you need a standard HTTP API for publishing and subscribing to data whilst tracking the conversation history.
This chapter will show you how to set up your own, self-hosted Matrix homeserver using the Synapse reference homeserver, and how to serve your own copy of the Riot web client. See the <linkxlink:href="https://matrix.org/docs/projects/try-matrix-now.html">Try Matrix Now!</link> overview page for links to Riot Apps for Android and iOS, desktop clients, as well as bridges to other networks and other projects around Matrix.
<linkxlink:href="https://github.com/matrix-org/synapse">Synapse</link> is the reference homeserver implementation of Matrix from the core development team at matrix.org. The following configuration example will set up a synapse server for the <literal>example.org</literal> domain, served from the host <literal>myhostname.example.org</literal>. For more information, please refer to the <linkxlink:href="https://github.com/matrix-org/synapse#synapse-installation"> installation instructions of Synapse </link>.
If the <code>A</code> and <code>AAAA</code> DNS records on <literal>example.org</literal> do not point on the same host as the records for <code>myhostname.example.org</code>, you can easily move the <code>/.well-known</code> virtualHost section of the code to the host that is serving <literal>example.org</literal>, while the rest stays on <literal>myhostname.example.org</literal> with no other changes required. This pattern also allows to seamlessly move the homeserver from <literal>myhostname.example.org</literal> to <literal>myotherhost.example.org</literal> by only changing the <code>/.well-known</code> redirection target.
If you want to run a server with public registration by anybody, you can then enable <option>services.matrix-synapse.enable_registration = true;</option>. Otherwise, or you can generate a registration secret with <command>pwgen -s 64 1</command> and set it with <option>services.matrix-synapse.registration_shared_secret</option>. To create a new user or admin, run the following after you have set the secret and have rebuilt NixOS:
In the example, this would create a user with the Matrix Identifier <literal>@your-username:example.org</literal>. Note that the registration secret ends up in the nix store and therefore is world-readable by any user on your machine, so it makes sense to only temporarily activate the <option>registration_shared_secret</option> option until a better solution for NixOS is in place.
<linkxlink:href="https://github.com/vector-im/riot-web/">Riot Web</link> is the reference web client for Matrix and developed by the core team at matrix.org. The following snippet can be optionally added to the code before to complete the synapse installation with a web client served at <code>https://riot.myhostname.example.org</code> and <code>https://riot.example.org</code>. Alternatively, you can use the hosted copy at <linkxlink:href="https://riot.im/app">https://riot.im/app</link>, or use other web clients or native client applications. Due to the <literal>/.well-known</literal> urls set up done above, many clients should fill in the required connection details automatically when you enter your Matrix Identifier. See <linkxlink:href="https://matrix.org/docs/projects/try-matrix-now.html">Try Matrix Now!</link> for a list of existing clients and their supported featureset.
Note that the Riot developers do not recommend running Riot and your Matrix homeserver on the same fully-qualified domain name for security reasons. In the example, this means that you should not reuse the <literal>myhostname.example.org</literal> virtualHost to also serve Riot, but instead serve it on a different subdomain, like <literal>riot.example.org</literal> in the example. See the <linkxlink:href="https://github.com/vector-im/riot-web#important-security-note">Riot Important Security Notes</link> for more information on this subject.