StateServer

StateServer, in the context of ASP.NET, refers to the out-of-process session state provider known as the ASP.NET State Service or StateServer mode. It stores session data outside the web application’s worker process, in a dedicated Windows service, allowing multiple web servers in a farm to share session state without relying on in-process memory.

The State Service runs as a Windows service named ASP.NET State Service (the executable is typically aspnet_state.exe). By default it listens on a network port (commonly 42424) and can be accessed by ASP.NET applications configured to use StateServer mode. To use it, applications set the sessionState mode to StateServer and provide a stateConnectionString that points to the State Server, for example tcp:servername,42424. This enables out-of-process storage of session data, improving resilience to worker process recycling and server restarts in a web farm.

Objects stored in session state must be serializable, since the state data is serialized for transmission to and from the state service. If the state service is unavailable or restarts, active sessions may be lost, as the data is held in memory by the State Service rather than in a durable store. StateServer is typically simpler to set up than SQL Server mode but may introduce network latency and is generally less scalable for large or highly dynamic session data compared with dedicated distributed caches or SQL-based session state.

StateServer is commonly used in older ASP.NET deployments or where a lightweight out-of-process store is desired. It is superseded in many modern scenarios by more scalable options, but remains a reference approach for out-of-process session state.