Azure Relay: No Inbound Ports Needed

Frequently asked questions

How does Azure Relay reach an on-premises service without an open inbound port?

The on-premises (private) side makes the outbound connection to a rendezvous point in Azure — the cloud side never initiates an inbound connection, so no firewall rule needs to be opened for it.

When would you use Relay instead of a VPN?

Relay suits reaching a single specific on-prem service without standing up full network-level connectivity. When more than a request/response link is needed, or the two sides don't need to be online at the same time, a VPN or a queue can be the better fit.

Read deeper on Azure

Twenty seconds gets the shape of an idea across. These go into how it behaves in production.

• How Azure Protects a Mobile App: The Full Request Flow, Layer by Layer

  Front Door, your API, Microsoft Entra ID, authorization and a private database — the five layers that stand between a mobile app and its data on Azure.

• Your Mobile App Is Leaking Its API Key — and Obfuscation Will Not Save It

  An APK or IPA is a zip file. Anything hardcoded inside it, including your API key, is already public — and here is how to get it off the phone for good.

• What Is Microsoft Foundry (Azure AI Foundry)? The Services, and When You Actually Need Them

  A plain tour of Microsoft Foundry for developers: the resource, projects, models, agents, tools, and when Azure OpenAI on its own is enough.