Using Z21 Handsets and WiThrottle Apps with BigFred

BigFred supports physical Z21 handsets and WiThrottle apps, pairing them to roster vehicles so you can drive with familiar hardware on your layout.

Some operators prefer a physical knob and buttons in their hand over a touchscreen — and BigFred is happy to oblige. You can connect a Roco Z21 multi-mouse, a WLANmaus, or any WiThrottle-compatible smartphone app to BigFred and pair it to a locomotive in your roster. Once paired, the handset controls that locomotive over the DCC bus just like the built-in web throttle does.

The Remotes page

Navigate to Remotes in the top menu to manage handset connections. The page is organised around your command stations: choose the station you want from the dropdown and BigFred shows the pairing controls and the list of currently connected clients for that station.

Only command stations that have the Z21 or WiThrottle server enabled appear in the dropdown. If no station appears, ask your admin to enable remote access on the relevant command station under Admin → Command Stations.

Supported protocols

BigFred supports two inbound handset protocols. Both run over your local WiFi network and require no extra software on your side of the connection.

Protocol	Transport	Default port	Typical clients
Z21	UDP	21105	Roco Z21 multi-mouse, WLANmaus, Z21 start handset
WiThrottle	TCP	12090	WiThrottle (iOS), Engine Driver (Android), and compatible apps

If your command station has both protocols enabled, BigFred shows a protocol tab-switcher so you can pair on either one independently.

Pairing overview

Connecting a handset to BigFred is a two-stage process:

1. Start pairing — In BigFred you click Generate Pairing (for the relevant protocol). BigFred enters a short pairing window and shows you the information you need to enter on the handset (a CV code for Z21, or a sentinel locomotive address for WiThrottle).
2. Connect on the handset — You enter the BigFred server’s IP address on the handset and follow the protocol-specific steps to complete the pair.

See the individual protocol pages for step-by-step instructions.

Connected clients list

Below the pairing panel you will find the Connected Clients table. It shows every handset currently connected to the selected command station in real time, including:

• Protocol — Z21 or WiThrottle
• Endpoint — the handset’s IP address and port
• Paired — whether the session is linked to a BigFred account
• User — the account the session is paired to
• Last seen — the last time BigFred received a packet from that handset
• Connected for — how long the handset has been connected
• Status — whether the session is idle-braked (see below)

You can remove your own paired session from this table by clicking the Unpair button next to your entry.

Idle brake

If a handset stops sending its heartbeat — for example because it goes out of range, loses WiFi, or the app is backgrounded — BigFred cannot know whether the operator is still in control. After the configured idle timeout (between 6 and 60 seconds, default 6), BigFred brakes the locomotive and releases the throttle slot. The entry in the client table will show the Idle braked badge.

An idle-braked locomotive is brought to a controlled stop. To resume driving, reconnect and re-pair the handset.

You can adjust the idle timeout when you start a new pairing session using the Handset brake seconds field on the Remotes page.

Protocol guides

Z21 Handsets

Connect a Roco Z21 multi-mouse, WLANmaus, or compatible Z21 UDP client to BigFred

WiThrottle Apps

Connect WiThrottle, Engine Driver, or any WiThrottle-compatible app over TCP