docs: add a config.json description

features/config-json.md

@@ -0,0 +1,85 @@
+---
+layout: default
+title: config.json
+parent: Features
+nav_order: 50
+has_children: false
+permalink: /features/config-json
+description: >-
+    You can set socket preferences in Mainsail
+---
+
+# {{ page.title }}
+{{ page.description }}
+
+There are several different modes of how Mainsail should react when a new session is opened. These settings can be done
+in the `config.json` file in your Mainsail root directory. A default config.json file should look like this:
+
+```json
+{
+    "hostname": null,
+    "port": null,
+    "remoteMode": false,
+    "instances": [
+
+    ]
+}
+```
+
+## Remote Mode
+
+This is the behaviour of mainsail when you use e.g. [my.mainsail.xyz](http://my.mainsail.xyz). If you have installed
+the Mainsail instance independently of the various moonraker instances (printers). For example, you use a smart home
+server or a NAS in your home network that can serve as a web server and is always accessible.
+
+To use this mode, open the `config.json` and change the value `remoteMode` to `true`. If you now open Mainsail, you
+should see this dialog.
+
+![Remote Mode](img/config-json-remoteMode.png){: width="50%" }
+
+In this mode, the socket settings are saved in the browser and you can add as many printers as you like to the Mainsail
+session using the "add printer" button.
+
+## Remote Mode with fixed printers
+
+This mode is very similar to the one described above, except that the Socket settings are not stored in the browser but
+directly in the config.json file and are therefore automatically available in every browser (pc, tablet, smartphone).
+
+With this mode, you have to switch the `remoteMode` as before to `true`, but then also have to specify a list of
+printers in the `instances` array. Here an example:
+
+```json
+{
+    "remoteMode": true,
+    "instances": [
+        { "hostname": "192.168.0.210", "port": 7125 },
+        { "hostname": "192.168.0.211", "port": 7125 },
+        { "hostname": "192.168.0.212", "port": 7125 }
+    ]
+}
+```
+
+In my example, 3 printers are added with the IP and with the default moonraker port 7125. When I now open mainsail, it
+looks like this:
+
+![Remote Mode](img/config-json-remoteMode-instances.png){: width="50%" }
+
+In my example, you can see that the first two printers are already connected and the third one has not been reached
+until now (it is currently switched off). For the first two printers, the name has also been loaded from the interface
+settings.
+
+## Fixed socket settings
+
+This case is rather unusual, but it is also possible with Mainsail. Here you can set up a printer directly if it does
+not match the currently opened url. For example, the web interface is available via `http://192.168.0.200` but the
+printer (Moonraker) has the IP address `192.168.0.210`. Then the `config.json` should look like this:
+
+```json
+{
+    "hostname": "192.168.0.210",
+    "port": 7125
+}
+```
+
+In this case, the specific printer simply opens immediately without the "select printer" dialog.
+