fix: Go2 EDU connection on Windows (multicast, AP IP, data2=3 AES, error messages)

[fractalsuar]

Summary

Four bugs found while connecting a Go2 EDU from a Windows 11 laptop in Access Point (dongle WiFi) mode. All four blocked connection independently.

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Bug 1 — Windows multicast scan always returns empty

File: src/proxy-plugin.ts

On Windows, machines almost always have multiple virtual network adapters (WSL, Hyper-V, VirtualBox). The OS routes the outgoing UDP multicast query on a virtual adapter rather than the physical WiFi — the robot never sees it and scan returns nothing.

Fix: Enumerate all non-loopback IPv4 interfaces with os.networkInterfaces() and create a separate sender socket per interface with socket.setMulticastInterface(iface). Also call addMembership / dropMembership per interface on the listener socket.

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Bug 2 — AP mode default IP is wrong for Go2 EDU

File: src/connection/modes.ts

DEFAULT_AP_IP was 192.168.12.1. The Go2 EDU has a two-computer architecture: a companion Ubuntu computer (eth0: 192.168.123.18, wlan0/hotspot: 10.42.0.1) and a separate main MCU at 192.168.123.161 where the WebRTC service actually runs on port 9991.

Fix: Changed DEFAULT_AP_IP to 192.168.123.161.

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Bug 3 — No way to auto-detect the correct robot IP

Files: src/proxy-plugin.ts, src/ui/connection-panel.ts

With scan broken and the default IP wrong, there was no way to find the robot without already knowing the address.

Fix: Added a /gateway endpoint to the Vite proxy that probes known Go2 candidate IPs on port 9991 and returns the first that responds. Added a Detect button next to the IP field that calls this and auto-fills the result.

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Bug 4 — data2=3 from /con_notify causes silent failure on Go2 EDU

File: src/connection/local-connector.ts

Go2 EDU with current firmware returns data2=3 from /con_notify, meaning the payload is AES-128-GCM encrypted with a per-device 16-byte key stored on the robot at /unitree/dev.key. The existing code only handled data2=2 (static key) and silently fell through on data2=3, causing an opaque failure with no useful error message.

Fix: Added a data2=3 branch that:

1. Checks localStorage for a cached per-device key (keyed by serial number)
2. If missing, prompts the user once to enter the 32-char hex key
3. Decrypts using AES-128-GCM with Unitree payload layout: [ ciphertext | nonce(12) | tag(16) ]
4. Caches the key on success so it is never asked again
5. On GCM tag mismatch (wrong key), flushes the cache and re-prompts up to 3 times

Also improved detectPort() to report per-port HTTP status or error in the failure message.

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Test environment

• Robot: Unitree Go2 EDU, firmware returning data2=3
• OS: Windows 11 with WSL + Hyper-V adapters present
• Mode: Access Point (laptop WiFi switched to Go2 dongle hotspot)
• Robot IP: 192.168.123.161:9991

Test plan

• Scan finds robot on Windows with multiple network adapters
• Detect button fills correct IP in AP mode
• Connection succeeds on Go2 EDU after entering device AES key once
• AES key remembered across page reloads
• Wrong key clears cache and re-prompts
• Existing Go2 (data2=2) and G1 connections unaffected

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