[cookingwithsimon]

What changes for the user

Before: a device with a static IP on another subnet never showed up. The status said "may have a static IP", and the tech had to guess the address and set the laptop by hand.

After:

• While the server runs, a new Found on the network list shows every device heard on the cable that didn't take a lease. That includes static devices on other subnets, each marked "Static IP on 192.168.1.x, which this laptop isn't on yet". Step 5 names the device too.
• Reach it adds a temporary address on the device's subnet, so Open WebUI works without stopping DHCP. If Wi-Fi is on that subnet, the app first offers to turn Wi-Fi off until Stop.
• Scan for static IPs finds quiet devices. It ARPs every address on the laptop's own subnet, the brand presets' factory subnets and any subnet a device was seen on, using a temporary address on each that's removed straight afterwards.
• Devices are named from mDNS/DNS-SD, SSDP/UPnP descriptions, PJLink, Art-Net, AES67/SAP, AMX beacons and NetLinx, Q-SYS and Shure discovery. Every query is read-only. Only addresses, ports and formats documented by the standard or the maker are used; the sources are in docs/vendor-discovery.md.
• With Npcap installed, the app also shows which switch, port and VLAN the laptop is on (from LLDP/CDP) and catches devices as they power up (from their ARP probe). Without Npcap, a hint offers the download and everything else still works.

How

• Core, Discovery/:
  • Packet readers for IPv4/UDP, Ethernet, ARP, LLDP, CDP, mDNS, SSDP and UPnP XML (DTDs refused), plus the vendor protocols.
  • DiscoveryTable merges sightings by MAC, falling back to IP.
  • SubnetPlanner chooses the subnets to scan and the helper addresses: .249 downwards, skipping documented factory addresses and subnets used by another adapter.
  • SubnetHelper runs Reach and the sweep against fake-able interfaces.
  • StatusChain names a found static device in step 5.
• Windows:
  • DiscoveryService runs for the session. It uses a raw socket in SIO_RCVALL IP-level mode (not promiscuous, so a busy video stream can't flood it), mDNS/SSDP/vendor sockets joined on the adapter, Windows' ARP table, and SendARP for the sweep.
  • NpcapCapture loads wpcap.dll at run time with a driver-side filter for ARP, LLDP and CDP only.
  • Temporary addresses go through AdapterSessionManager, which gains RemoveTemporaryAddress, so Stop, exit and a crash all remove them.
  • A second firewall rule ("ProDHCPServer (discovery)") covers this exe on wired adapters and is removed on Stop.
  • SSDP descriptions are fetched only from devices this adapter can reach, so the request never goes out over Wi-Fi.
• App: the found-device list with Reach it, Open WebUI and Copy IP, the scan button and progress, the switch-port line and the Npcap hint.

Testing

• Core tests pass (211, 49 new). They cover every protocol parser, table merging, subnet planning, Reach retrying after a duplicate address, the sweep removing its address even when cancelled, and the step 5 wording.
• Windows CI is green. New integration tests cover the ARP table and SendARP against the runner's gateway, the Npcap check, a discovery socket plus raw sniffer receiving a PJLink reply, and the discovery firewall rule.
• Hardware checklist added: docs/hardware-test-phase3.md.

🤖 Generated with Claude Code

https://claude.ai/code/session_01KZvcgLYKFKnCYgDw2Bxw5e

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Generated by Claude Code