Introduction
Hybrid Connections is both a service in Azure and a feature in Azure App Service. Within App Service, Hybrid Connections can be used to access application resources in any network that can make outbound calls to Azure over port 443. Hybrid Connections provides access from your app to a TCP endpoint.Architecture
Hybrid Connections requires a relay agent to be deployed where it can reach both the desired endpoint and Azure. The relay agent, Hybrid Connection Manager (HCM), calls out to Azure Relay over port 443. From the web app site, the App Service infrastructure also connects to Azure Relay on your application’s behalf. Through the joined connections, your app is able to access the desired endpoint. The connection uses TLS 1.2 for security and shared access signature (SAS) keys for authentication and authorization. When your app makes a DNS request that matches a configured Hybrid Connection endpoint, the outbound TCP traffic is redirected through the Hybrid Connection.
The on-premise endpoint must be assigned with a machine name or domain name. The connections are not recommended using IP address. Ref: Hybrid Connections in Azure App Service