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Remote desktop without port forwarding

The classic way to reach a computer at home is to open a port on the router and point it at the machine. That fails more often every year. Many mobile, satellite and fibre providers put whole neighbourhoods behind one shared IPv4 address (carrier‑grade NAT), so there is no port of yours to open. Rented flats, offices and parents’ houses come with routers nobody will let you near. ManyScreens needs neither.

How it connects without an open port

1. Both ends dial out. The app on your computer keeps one connection open to the ManyScreens server: a WebSocket on port 443, the port every web page uses. The browser you watch from does the same. Nothing ever has to reach in.
2. WebRTC looks for a direct path. The two ends swap the addresses they can see, and their routers usually let the stream through in both directions. On the same network the picture never leaves the building.
3. Where no direct path exists, a relay carries it. The relay listens on UDP and TCP and on TLS over port 443, so it gets through networks that allow only web traffic. The stream is encrypted end to end with DTLS‑SRTP, and the relay forwards packets it has no key for.

If a proxy kills WebSockets on the viewing side, the browser switches to ordinary HTTPS requests by itself after six seconds. After two failed attempts at a direct path, it goes straight to the relay.

When the provider changes your address

Many home connections are given a new public IP address every night, which leaves connections looking open when they are long dead. The ManyScreens app notices 90 seconds of silence, drops the connection and dials again, retrying every few seconds and backing off to every 30. You do not have to restart anything.

What the relay costs in quality

Route	Free	Pro
Direct	Up to 2560 px wide, 30 fps	The same on Auto, or 60 fps on High
Relay	1280 px, 10 fps	1280 px, 15 fps on Auto, or any setting up to High by hand

Check a network before you rely on it

The connection check runs in the browser against the same servers a real session uses. It tests whether a WebSocket survives, which addresses it can see, and whether the relay answers over UDP, TCP and TLS. It needs a free account. The app on the far computer needs one thing from its own network: an outgoing WebSocket on port 443.

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