Azure App Service is a popular platform-as-a-service offering, but two related resource limits often catch developers off guard: outbound TCP connection exhaustion and SNAT port exhaustion. This guide provides a practical walkthrough of both issues using .NET code, explaining how they manifest as SocketException and connectivity failures. The article covers the underlying mechanics—worker instance TCP limits and Azure's outbound load balancer SNAT port allocation—and demonstrates how to reproduce the problems in a controlled environment. Beyond diagnosis, it offers concrete mitigation strategies such as connection pooling, using managed identity instead of service principals, and scaling out to distribute load. For cloud architects and backend engineers running production workloads on Azure, understanding these exhaustion patterns is essential for building resilient applications. This guide serves as both a troubleshooting reference and a preventive design pattern resource.
Hands-on guide to diagnosing and preventing connection and SNAT port exhaustion in Azure App Service with .NET code examples.