Web interface

The web interface allows configuration and monitoring through a browser, without a USB cable and without a broker. It is useful for fixing the MQTT connection (mqtt_host, mqtt_mode, port, credentials) that cannot be changed through config because the node is not connected to the broker.

Opening it

• http://sentinel-<last 6 digits of MAC>.local over mDNS (macOS and iOS directly; Windows 10+ and Linux usually). Example: MAC a2cb8ff8768d → http://sentinel-f8768d.local.
• Or by IP: shown on the LCD (Jaringan menu), in the MQTT status (ip), and in the gateway’s DHCP table.
• User admin, default password sentinel (the same on all units). Change it in the System tab. A yellow banner shows while the password is still the default, and config/reported contains web_pw_default: true.

Log in through the form on the page itself. The Sign out button is at the top right, as is the EN | ID language switch.

Sessions: one user at a time

• Only one session across all browsers and devices. A successful login takes over: the old session immediately becomes invalid and its page shows “Someone signed in from another browser or device”.
• A session ends by itself after 10 minutes without activity (click, tap, key press, or scroll; automatic refreshes of the Status tab do not count).
• Sign out ends the session on the device, so all tabs and browsers become invalid immediately.
• Sessions live only in RAM: a reboot (including after a firmware change and factory reset) ends the session. Moving to another IP address also means a new login, because cookies are per host.

Tabs

Tab	Function
Status	network (IP, gateway, MQTT, NTP servers with answer status, last NTP sync), device date and time, temperature, inputs, outputs, power, Modbus device summary, free memory (heap_free, heap_min) and the number of outgoing messages dropped for being too large (oversize_dropped), alarms. Refreshes every 3 seconds
Configuration	all keys (the form is generated from the firmware schema); only changed keys are sent; rejected keys are marked with the reason; connection changes trigger a reboot. Includes entering a private CA for TLS
Rules	view and delete rules (not add or edit; that is for the server or celestianctl): set summary (rules_ver, count, size, hash, remaining confirmation time), each rule with its state, its condition and actions in a sentence, and the set content as JSON. Refreshes every 4 seconds
Devices	read-only monitoring of Modbus devices: a summary (OK, problem, waiting, disabled) and one row per source. Click a row for its metric values; the Show problems only filter
Sources	Modbus source and RS-485 bus settings, add a source from a profile (shows the metric names that will be created and rejects up front names the node would certainly reject), the profile list, and profile import. See Modbus sources
Groups	telemetry group editor with confirm_s testing and a rollback button. See Telemetry groups
Control	identify, reboot, scan the 1-Wire bus and bind a ROM to a slot, switch outputs on/off
System	information, update firmware, change password, factory reset

mqtt_pass is write-only: its value is never sent back (the page only knows whether it is filled).

Caution

If the device is managed by Celestian, the retained configuration from the server is applied again on every reconnect and can overwrite non-connection changes made in the web. The page shows a warning.

What each tab looks like

Status tab.

Configuration tab (workspace, channel, and MQTT user values are masked).

Control tab.

Devices tab (no Modbus sources yet).

Sources tab.

Groups tab.

Rules tab.

System tab.

Updating firmware from the web

System tab, “Update firmware” card: choose the firmware.bin file, optionally fill the SHA-256, then “Upload and install”. Suitable when the unit has no route to the broker or the gateway’s OTA server.

• The page rejects files that are not an ESP32 image or are larger than the slot (6.25 MiB). If a SHA-256 is given, the hash of the whole content must match.
• The image is written to the spare OTA slot (progress is shown), then the unit restarts; the old version remains for rollback.
• The new image is “pending verification”. An image installed through the web counts as healthy if Ethernet is stable for 60 seconds and you successfully log in to the new firmware’s web. Otherwise, after 10 minutes the unit returns to the previous version.
• One update at a time: if an OTA over MQTT is running, the upload is rejected, and vice versa.

See also Firmware and OTA.

Security

• Plain HTTP, no TLS: the password and session cookie travel as-is on the LAN. Use it on a trusted network (the rack LAN).
• Failed logins are limited per client address: 5 consecutive failures = locked for 30 seconds, then 60, 120, 240, 300 seconds.
• The password is stored as a salted hash in a separate area. cmd reset_config and config from the server do not touch it, and it never enters configuration reports. Password rules: 6–64 ASCII characters.
• Every POST request must carry the X-Sentinel: 1 header, and the session cookie is SameSite=Strict, so other pages in the browser cannot use a stored session.
• One session only: anyone who knows the password can kick out the signed-in user. The password is the only secret.
• Anyone with the web password can install any firmware.

Forgotten password

The password can only return to default through factory reset (which also erases settings), using the touch sequence on the device or reset_factory in USB serial. See Reset and moving racks.

Language

The interface has two languages, English (default) and Indonesian. The choice is stored on the device, not in the browser, so it applies to all browsers and survives reboot or OTA. Factory reset returns the language to English. The LCD is unaffected and remains in Indonesian.

HTTP API

All /api/* calls need a session, except /api/login. Without a valid session the reply is 401 with {"ok":false,"msg":"login diperlukan","reason":"none|idle|replaced|logout"}.

Path	Contents
POST /api/login	{"user":"admin","password":"..."} → Set-Cookie: sentinel_sid=.... Rate limited per client address (429)
POST /api/logout, GET /api/session	end the session; extend the session
GET /api/info, GET /api/status	identity and network; same as the serial status command
GET /api/config, POST /api/config	the effective configuration; send {"key":value,…} → {ok, changed, reboot, rejected}
GET /api/schema	key list: type, range, default, reboot required
POST /api/cmd	{"action":"reboot|identify|rescan|output",…}
GET /api/rules, POST /api/rules	the effective rules set; replace the whole set
GET /api/devices	Modbus device summary; /api/devices/<id> for one source
GET /api/sources, POST /api/sources, …/confirm, …/rollback	Modbus sources
GET /api/profiles, POST /api/profiles, …/confirm, …/rollback	Modbus profiles
GET /api/tgroups, POST /api/tgroups, …/confirm, …/rollback	telemetry groups
POST /api/firmware	body = the contents of firmware.bin (header X-Sentinel: 1, X-Sha256 optional)
POST /api/lang, POST /api/password	language; change password {"old":"…","new":"…"}
POST /api/factory-reset	{"password":"…","confirm":"RESET"}

Example with curl (log in once, keep the cookie; this takes over any open browser session):

curl -c jar -H 'X-Sentinel: 1' -d '{"password":"<password>"}' http://sentinel-f8768d.local/api/login
curl -b jar http://sentinel-f8768d.local/api/info
curl -b jar -X POST -H 'X-Sentinel: 1' http://sentinel-f8768d.local/api/logout

HTTP Basic (curl -u) is not accepted.