You need to accept the SIP NOTIFY traffic from the QoE Agent Client Gateway by creating or reusing a signaling group (see Creating and Modifying SIP Signaling Groups) to accept SIP traffic from Client. The listening port will be the port provide in the System tab of the QoE Agent Client Gateways.
To configure the QoE service as a Server:
In the WebUI, click the Settings tab.
In the left navigation pane, go to System > QoE.
In the QoE Service panel, select Server from the QoE Agent Type list box.