Lync Web App is a web application that communicates over HTTPS. By default, this traffic is over port 443 TCP and is secured with certificates. Administrators can adjust this port if desired.
Tip
Although Lync Web App communicates only over 443 TCP for web traffic, the A/V plugin communicates directly with the Conferencing Server or Edge Server using standard media ports. Keep this in mind when planning your Lync Web App deployment.