Overview
Secure File-Transfer Gateway – Cloud-to-On-Prem Delivery. BlueScope Steel North America needed vendors and cloud applications to deliver files to file shares that sit behind the corporate VPN—securely, auditably and at sizes up to 10 GB.
Apps By TAP built an OAuth-secured Azure gateway that accepts uploads in the cloud and delivers them to on-prem servers through Azure Service Bus and a Windows worker service, with an SDK that makes it reusable across internal apps.
The Challenge
- Outside-in transfers: Vendors couldn’t reach BlueScope’s VPN-protected file shares.
- Enterprise-grade security: The solution had to satisfy SOC 2 controls, MFA and auditing.
- Large payloads: Drops of up to 10 GB meant latency spikes risked timeouts.
- Reusable interface: Multiple internal apps needed a plug-and-play SDK.
Our Approach
OAuth-secured ingress API
Azure App Service hosts ASP.NET Core endpoints protected by IdentityServer (OAuth 2.0).
Message-driven workflow
Each upload request stores the files in Blob Storage and posts metadata to Azure Service Bus. This decouples the caller from on-prem network latency.
On-prem transfer worker
A Windows service running in BlueScope’s DMZ dequeues messages, streams blobs over SMB to the designated file servers and records checksums in SQL Server.
Extensible .NET SDK
Internal teams integrate with three lines of code—upload, query status and receive webhook callbacks on completion.
Technology Stack
- ASP.NET Core Web API and IdentityServer – the secure ingress. See our APIs & backends service.
- Azure App Service, Blob Storage and Service Bus – scalable, decoupled cloud infrastructure. Part of our cloud solutions work.
- C# worker services – the on-prem transfer agent.
- SQL Server – transfer records and checksums.
- Internal .NET SDK – reuse across BlueScope applications.
Results & Impact
The solution enabled BlueScope to transfer files to its on-prem file servers, ensured compliance and gave BlueScope a scalable blueprint for future cloud-to-on-prem workflows. The same Service Bus pattern powers the Tekla Web Service we built for BlueScope.
