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Discovery

Document Context

  • Purpose: Explains mDNS/DNS-SD device discovery for locating whatwatt Go devices on local networks without knowing IP addresses
  • When to use: Network setup, device commissioning, troubleshooting connectivity, automated device detection
  • Prerequisites: Understanding of local networks, familiarity with mDNS/Bonjour/Avahi concepts
  • Related to: Network configuration, device setup, HTTP service access, Modbus TCP setup
  • Validates against: Live mDNS broadcasts from whatwatt Go devices with firmware 1.2+

Key Facts

  • Discovery protocol: mDNS/DNS-SD (Bonjour/Avahi compatible)
  • Hostname pattern: whatwatt-XXXXXX.local (XXXXXX = last 6 hex digits of device ID)
  • HTTP service: _http._tcp on port 80 with Web UI instance name
  • Modbus service: _modbus._tcp on port 502 (when enabled)
  • TXT records: Device ID (12-hex uppercase), device type (100)
  • Service subtype: _server for HTTP (shows as "Web Site" in browsers)
  • Network requirement: Device and client on same local network/VLAN
  • Auto-discovery: Enables zero-configuration device access

Finding the device on your local network

Devices advertise themselves via mDNS/DNS‑SD.

  • Hostname: whatwatt-<XXXXXX>.local
  • Prefix whatwatt is lowercase, suffix XXXXXX is the last 6 hexadecimal UPPERCASE digits of the device ID
  • HTTP service: _http._tcp with instance name whatwatt Go <XXXXXX> WebUI
  • TXT records: id=<12-hex uppercase device ID>, type=100
  • Subtype: _server (some browsers show “Web Site” badges)
  • Modbus (optional): _modbus._tcp with instance name ModbusTCP Slave <XXXXXX> on configured port (default 502)

Example result

ens38 IPv4 whatwatt Go 9F8124 WebUI Web Site local
hostname = [whatwatt-9F8124.local]
address  = [192.168.99.176]
port     = [80]
txt      = ["id=A842E39F8124" "type=100"]

If Modbus is enabled you may also see:

ens38 IPv4 ModbusTCP Slave 9F8124 _modbus._tcp local
hostname = [whatwatt-9F8124.local]
port     = [502]

Summary

  • Hostname pattern: whatwatt-XXXXXX.local (XXXXXX = last 6 hex digits of device ID)
  • Services: _http._tcp (always), _modbus._tcp (when Modbus is enabled)
  • TXT (HTTP): id=<12-hex>, type=100
  • Ports: 80 (HTTP), 502 (Modbus default)