Free macOS helper that exchanges GOOSE and Sampled-Values frames with the station bus via libpcap. JCH IED Studio (iPad/Mac) connects to it over WebSocket.

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New in 0.2.1: Now also receives GOOSE and Sampled Values frames with a VLAN tag (802.1Q) — the norm in substation networks. Older versions did not receive such frames. Update recommended: simply drag the new version over the old one in Applications; pairing code and settings are kept.

Why not via the Mac App Store? The Bridge needs libpcap access to raw Ethernet frames, which the App Store sandbox forbids. That’s why we ship the Bridge directly as a signed .dmg, notarized by Apple.

System requirements

  • macOS 13 (Ventura) or newer — Apple Silicon and Intel both supported (Universal Binary).
  • Mac must be on the same network as the iPad / second Mac running the app.
  • Administrator rights for the first launch (BPF access setup — see below).

Installation

1. Open the DMG and drag the Bridge into /Applications

Download the latest .dmg, open it by double-clicking, and drag JCH 61850 GOOSE Bridge into the Applications folder.

2. First launch

The Bridge is signed with an Apple Developer ID certificate and notarized by Apple. On first launch, macOS asks once whether to open an app downloaded from the internet — confirm with Open.

3. Grant BPF access (one-time)

libpcap reads and writes raw Ethernet frames via the /dev/bpf* device. Standard users cannot access these, so elevated rights are required once. Two options:

Option A — Permission helper (recommended): The Bridge ships with a small setup assistant. On first launch, a notice window appears with a Set up BPF permissions button. Clicking it opens an admin prompt and adjusts /dev/bpf* permissions. Afterwards the Bridge runs without further intervention.

Option B — Manually via terminal:

sudo chmod 644 /dev/bpf*

This setting persists until the next reboot. To make it permanent, install a LaunchDaemon — the helper from Option A does this automatically.

4. Select the network interface

After launch, the Bridge sits in the menu bar. Click → Select interface. From the list, pick the Ethernet interface connected to the station bus (e.g. en0 or a USB-Ethernet adapter such as en7).

VLAN-tagged packets: If your station bus uses VLAN tags, the Bridge asks for admin rights on first send and automatically creates a matching vlanXXX interface. The kernel sets the 802.1Q tag — pcap_sendpacket alone cannot do this on macOS.

5. Connect from JCH IED Studio

  1. In the app: tab Bridge.
  2. Enter the WebSocket URL: ws://<Mac-IP>:8765 (Bridge default port).
  3. Tap Connect — the status dot turns green.
  4. GOOSE/SV tabs now display live frames from the selected interface.

What the Bridge does — and what it doesn’t

Function Bridge
GOOSE receive (EtherType 0x88B8) ✓
GOOSE send (with retransmission profile) ✓
Sampled Values receive (EtherType 0x88BA) ✓
Sampled Values send (raw APDU bytes) ✓
VLAN tagging via kernel vlanX interface ✓
MMS / Reports / Control services not needed — handled directly by the app over TCP
Bonjour advertising (app discovers Bridges automatically) ✓

Uninstall

  1. Bridge menu-bar icon → Quit.
  2. Drag JCH 61850 GOOSE Bridge.app from /Applications to the Trash.
  3. If a LaunchDaemon was installed for persistent BPF rights:
sudo launchctl unload /Library/LaunchDaemons/com.jch.bpf.plist
sudo rm /Library/LaunchDaemons/com.jch.bpf.plist

Questions, bugs, requests

See Support.