Free app for iPhone & iPad · in App Store review

A Modbus TCP client that lives in your pocket

Not a laptop tool you fetch from the office — a client that's already with you at the machine. One scan finds every Modbus device on the subnet. Registers get names, types and scaling with a live value preview as you type. Dashboards trend them, an operator panel writes them — with guard rails.

Coming soon tothe App Store Android — get notified

Made for how Modbus actually gets used

One scan, every device

One sweep of the subnet finds Modbus devices — and fingerprints EtherNet/IP and Siemens S7 controllers while it's at it. Tap a device card and the add form is prefilled with IP and port.

Registers with names

Address, data type, scaling — entered once, named forever. The live value preview updates as you type, so a wrong type or offset is obvious before you save it.

Find the register by acting

Patent-pending: press the machine's real button in the app's rhythm, or nudge a setpoint on the machine's own display — the app returns the register that answered.

Dashboards & trends

Number, gauge, LED and trend tiles across pages — a VFD's speed and current next to the meter's kilowatts, live. Mixed brands share one screen.

Writes with guard rails

Every write is validated against the point's type and limits and asks for confirmation. Hold-to-run buttons release the moment the app loses focus. One-time unlock, no subscription.

Alarms from bits

Map alarm words to operator texts — every bit one message. A red banner over every tab, an alarm journal of appeared and cleared, and unnamed bits get named the moment they first fire.

Straight from the app

Equipment list in the LineKeeper Modbus TCP client app: a packaging line with two PLCs, a mixer, and the built-in demo line
Machines, not bare IPs — one piece of equipment can hold several devices
Live dashboard in the LineKeeper app trending values from two controllers: speed gauge, part counter, motor current trend and temperature
Named registers live on dashboard tiles — gauges, counters, trends
Guarded register write in the LineKeeper app: the allowed range is shown and the value asks for confirmation before it reaches the Modbus device
Writes show the allowed range and confirm before touching the device

From "what's on this network?" to a working panel

  1. Get on the device's network. Plant Wi-Fi that routes to it, or a USB-C Ethernet adapter. If the phone can ping the device, the app can poll it.
  2. Scan — or type an IP. The scan finds Modbus TCP devices on the subnet; adding by hand is one field for the IP and one for the port (502 by default).
  3. Name your registers. Address, type, scaling — with the live preview confirming each one as you go. The map saves into the machine profile.
  4. Drop them on a dashboard. Values, gauges, LEDs, trends — organized into pages, every tile labeled with the device it reads.
  5. Add the panel buttons. Start/stop pulses, latching switches, setpoints, status lamps. Full-screen panel mode keeps the phone awake at the machine.
  6. Share the profile. Export it as a file — a colleague imports it and gets the whole register map and every screen on their phone.

Not just Modbus: the same app speaks EtherNet/IP to Allen-Bradley CompactLogix/ControlLogix (tag list read straight from the controller) and S7comm to Siemens S7-300/400/1200/1500. One machine in the app can mix all three behind a single dashboard and panel. See the full app tour →

FAQ

Modbus questions

Which devices does it work with?

Anything speaking Modbus TCP: Schneider, AutomationDirect and Click PLCs, VFDs, energy meters, temperature controllers, remote I/O, protocol gateways. Serial Modbus RTU devices are reachable through a Modbus TCP gateway — to the app they look like any other TCP device.

How do I know what a register means?

The device's manual holds the register map — and the app's live preview confirms each entry as you type it. If the manual is long gone, Find by action locates a point from the machine's own behavior: press the real button in the app's rhythm, or nudge a setpoint one step, and the app returns the register that followed.

Can it write?

Yes — deliberately. Every write asks for confirmation and is validated against the point's type and limits; hold-to-run buttons release the moment the app loses focus. Reading, dashboards and alarms are free; writing is a one-time in-app purchase, no subscription.

Do I need a gateway, OPC server or cloud account?

No. The app speaks Modbus TCP directly to the device over the local network. There is no cloud relay: if the phone can reach the device's IP, the app can poll it.

Is there an Android version?

Android is in development — leave your email and you'll get one message when the beta opens, nothing else.

Get the app

Free download, the day Apple approves it

LineKeeper is in App Store review right now. The button goes live the moment it's approved — free for iPhone and iPad. Until then, the app page has the full tour and screenshots.

Coming soon tothe App Store In App Store review · free when it lands