The Application Server installation process provides an option for selecting the Windows Process Activation Service (WAS) for applications that are built on Windows Communication Foundation (WCF). Installing WAS also installs the Web Server (IIS) role.

WAS is a new process activation mechanism for the Windows Server 2008 operating system that is also available on the Windows Vista® operating system. It retains the familiar Internet Information Services (IIS) 6.0 process model (application pools and message-based process activation) and hosting features (rapid failure protection, health monitoring, and recycling). However, it removes the dependency on Hypertext Transfer Protocol (HTTP) from the activation architecture. IIS 7.0 uses WAS to accomplish message-based activation over HTTP. In addition to HTTP, WCF can also use the non-HTTP protocols that are supported by WAS, such as TCP, MSMQ, and Named Pipes, to provide message-based activation. This makes it possible for applications that use communication protocols to take advantage of the IIS features, such as process recycling, rapid fail protection, and the common configuration system, that were previously available only to HTTP-based applications.

Each application that is under the control of WAS has a Uniform Resource Identifier (URI) address that identifies the network protocol that WAS uses to activate the application.


For WAS activation to work, the network protocol that is specified in the URI must be enabled on the server and allowed to pass through any firewalls that are in place. For more information about allowing firewall exceptions, see Windows Firewall and Windows Firewall with Advanced Security (

If you enable TCP Activation, Application Server creates a firewall exception rule that opens TCP port 808. (You can specify a different port by changing the URI to specify a different port.) So that the TCP Listener can start listening on port 808, you must also create a default Web site that uses net.tcp.