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UltraVNC or any VNC is UNUSABLE over ADSL

Since a few weeks (months? ) it looks like that some internet providers LIMIT the bandwidth over ports above 1024... at least in France
(maybe an attempt to counter Peer to Peer ?).

Consequently all the softwares that use TCP or UDP ports > 1024 have become simply unusable over ADSL/Cable connections, even worse than over RTC modems.
When Web browsing still flies...

The solution is to configure your UltraVNC server (or other software) to use ports below 1024 (between 800 and 1024 for instance).

Here is how to configure UltraVNC for port 80 (http port, which will never be limited as it is used for web browsing ). If you already have a web server listening on this port, use a port like 8xy or 9xy.

1. In WinVNC properties page: Ports: Main: 80 (or 8xy)
2. In your router ADSL Modem configuration: you must route port TCP 80 (or 8xy). Restart your modem/router
3. From the outside: run vncviewer with Server = YourServerIP::80 (or YourServerIP::8xy)

-> UltraVNC is flying again

This trick also works with any software that usually use high ports (like RDP and so on...)
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very low speed and erratic result can happen with bad network interface card configuration

always bad result: (very very slow and erratic network connection)


10 Mbit/s Half-Duplex <---> 10 Mbit/s Full-Duplex
10 Mbit/s Half-Duplex <---> 100 Mbit/s Full-Duplex
100 Mbit/s Half-Duplex <---> 10 Mbit/s Full-Duplex
100 Mbit/s Half-Duplex <---> 100 Mbit/s Full-Duplex


middle result: (sometime could fail depend of driver and switch/broadband router)
auto mode negociation speed and duplex (from factory)


best result: (manual under normal condition and connection)
10 Mbit/s Half-Duplex <---> 10 Mbit/s Half-Duplex
10 Mbit/s Half-Duplex <---> 100 Mbit/s Half-Duplex
100 Mbit/s Half-Duplex <---> 100 Mbit/s Half-Duplex
100 Mbit/s Full-Duplex <---> 100 Mbit/s Full-Duplex
100 Mbit/s Full Duplex <---> 1000 Mbit/s Full Duplex
1000 Mbit/s Full Duplex <---> 1000 Mbit/s Full Duplex