Windows Desktop Agent (.NET/C#) — eSSL Biometric Device Integration via zkemkeeper.dll

We're building a lightweight Windows desktop agent for our SaaS gym management platform. The agent connects to eSSL/ZKTeco biometric fingerprint devices on the local network and syncs data with our cloud backend.

WHAT THE AGENT DOES:
- Connects to eSSL devices via TCP/IP (port 4370) using zkemkeeper.dll (COM/ActiveX)
- Polls our REST API for pending commands (sync users, set membership expiry dates, enable/disable users)
- Executes SDK commands on the device and reports results back to cloud
- Runs as a system tray app, auto-starts on boot
- Includes a first-run setup wizard (enter API key → auto-discover device on LAN → connect)

KEY SDK FUNCTIONS:
Connect_Net, SSR_SetUserInfo, SetUserValidDate, SSR_EnableUser, SetDeviceTime2, ReadNewGLogData, SearchDevice, GetSerialNumber, BeginBatchUpdate/BatchUpdate

TECH STACK:
- .NET 8+ (WinForms or WPF)
- C# with COM interop for zkemkeeper.dll
- REST API client (HttpClient) for cloud communication
- Single .msi/.exe installer (Inno Setup or WiX)

WE PROVIDE:
- Complete developer brief document (12 sections, all SDK functions documented)
- eSSL Standalone SDK v2.3 manual + Communication Protocol SDK with C# samples
- Physical eSSL F22 device for testing (can ship to you)
- Cloud API endpoints (we build these)
- eSSL vendor support contact for SDK issues

REQUIRED SKILLS:
- C#/.NET desktop application development
- COM/ActiveX interop experience
- TCP/IP socket communication
- Experience with biometric SDKs (eSSL/ZKTeco preferred, not mandatory)

TIMELINE: Can be decided

Attach your relevant portfolio and let me know if you've worked with eSSL/ZKTeco devices before.