Network architecture

The application uses a two-process model with loopback-only communication between the Electron UI and the SASS backend.

The application uses a two-process model. All communication between the Electron UI and the SASS backend occurs exclusively over the loopback interface (127.0.0.1).

Figure 1. Network architecture


┌─────────────────────────────────┐
│  Sennheiser Firmware Updater UI │  (Electron, user session)
└──────────────┬──────────────────┘
               │ IPC / localhost only
               ▼
┌─────────────────────────────────┐
│  SASS Backend  localhost:8181   │  (.NET 8 service, spawned by UI)
└──────────────┬──────────────────┘
               │ mDNS (UDP 5353) — discovery
               │ HTTPS (SSCv2)   — EW-DX, chargers
               │ SSC over UDP 45 (SSCv1) — L 6000
               ▼
┌─────────────────────────────────┐
│  Sennheiser Devices (LAN)       │
└─────────────────────────────────┘

Internal Loopback Endpoints (no firewall exception required)

Table 1. Internal loopback endpoints
Endpoint	Protocol	Purpose
http://localhost:8181/api	HTTP	REST API for device management and firmware operations
http://localhost:8181/api/health	HTTP GET	Backend health monitoring
http://localhost:8181/websocketHub	SignalR / WebSocket	Real-time device events

These endpoints bind to localhost only and are never reachable from the network.