If you're reviewing ScreenSharePRO for your network, the short answer is: no inbound ports and no port forwarding. Every connection starts from the computer and goes outward. Here is each one.
Do I need to open any inbound ports?
No. Neither computer listens for connections from the internet, so there is nothing to forward on the router and no inbound firewall rule to add.
Which outbound connections does it make?
| Purpose | Destination | Protocol and port |
|---|---|---|
| Sign-in, finding the other computer (signalling) and update checks | screensharesite.azurewebsites.net | HTTPS and secure WebSocket, TCP 443 |
| Discovering a direct path between the two computers (STUN) | stun.l.google.com | UDP 19302 |
| Relay, when no direct path exists (TURN, desktop app only) | The relay provider named in our Privacy Policy | Port 3478 |
| The session itself | The other computer, or the relay | UDP |
The session's screen, keyboard and mouse data is encrypted end to end with WebRTC DTLS-SRTP, including when it passes through the relay, which can't read it.
What if our network blocks UDP?
Sessions travel over UDP, either directly between the two computers or through the relay. If outbound UDP is blocked completely, a session can't be set up. If your policy only allows specific ports, allow outbound UDP 19302 and port 3478 so sessions can fall back to the relay when a direct path isn't available.
Does the browser web app use the relay?
No. The browser web app connects directly only. If the desktop app connects on a network where the browser doesn't, a strict firewall or VPN blocking the direct path is the likely reason, and the desktop app is the answer there.
How can I tell if a session is relayed?
The viewer shows a Relayed badge. Its explanation reads: "Video is going through a relay server because a direct connection to the host could not be made. Expect higher latency and a lower frame rate. A VPN or a restrictive firewall is the usual cause." See how to fix a slow connection.
Proxies, VPNs and Wake-on-LAN
- There is no proxy setting in the app.
- VPNs are the most common reason a session is relayed. On a PC with several network adapters, Network connection to use in Settings picks which one ScreenSharePRO uses.
- Wake-on-LAN sends a UDP broadcast to ports 9 and 7 on the local network only. It doesn't cross the internet.