What is Citrix License Server
The Citrix licensing system involves three components: the license server for managing licenses, licenses for each product that you purchase and the monitoring and metering functions built in each product. the Citrix License Server is a lightweight component that can be installed on the same system as a Citrix product for smaller deployments, or on one or more dedicated systems for larger deployments.
Each Citrix product environment must have at least one shared or dedicated license server. Citrix products seek permission from this license server to run. The first time a user connects to a Citrix product (for example, the user starts a published application), the product requests a license from the license server. When the license server grants a license request, the Citrix product reserves a license for its use. Reserving licenses for this purpose is known as checking out licenses. When the user logs off from the product server, the product returns the license to the license server. This process is known as checking in licenses. Citrix products use a continuously open connection to the license server to check out licenses. Every time a Citrix product starts, it opens a connection to the license server by checking out the startup license. The startup license is a Citrix system file that enables Citrix products to maintain a connection to the license server.
Figure 1 : Citrix Products accessing the License server