Server ports are used to connect to either chassis IOM or FEX modules for c-series management. If you look at the configuration of the server port from the CLI you will see it is in switchport mode fex-fabric. Currently, it is not possible to connect a c-series rack server directly to the FI without a FEX module in between.
Below is some information on managing c-series rack servers through UCSM if you are interested:
What Biran pointed out above is correct, let's remeber that IOMs and Nexus 2K (used to integrate a rack server to UCSM), both are Fabric Extenders (FEX's) in consequence, one or another connection will require you to configure those ports as server ports.
This process only requires a right-click on the port and choose the optio to configure as such.