6 min read•Updated October 2026
WHMCS Products Reseller Hub — B2B Webhook Architecture
Technical specification of the 2-way asynchronous webhook engine and automated catalog sync protocol for B2B hosting networks.
Architecture Overview The Products Reseller Hub enables a master WHMCS provider to act as a wholesale upstream for multiple downstream WHMCS installations.
Downstream Handshake Protocol 1. **Catalog Query**: `GET /modules/addons/products_reseller/api/v1/catalog` Returns wholesale packages, configurable option groups, operating systems, and wholesale currency rates.
2. **Order Placement**: `POST /modules/addons/products_reseller/api/v1/orders/provision` Downstream WHMCS submits an order payload authenticated via HMAC-SHA256 bearer token.
3. **Asynchronous Webhook Callback**: When the hypervisor completes server deployment, upstream WHMCS posts server IP, credentials, and root password back to the downstream webhook URL: `POST https://downstream-host.com/modules/addons/products_reseller_client/webhook`