UltraVNC is a free, open-source remote desktop program for Windows. It shows another computer’s screen on your own and lets you work on it with your mouse and keyboard. It uses the RFB protocol on which VNC software is built. Its GNU GPL license allows use at no cost in both personal and commercial settings.
Server and viewer roles
An UltraVNC session involves two programs. UltraVNC Server runs on the computer being controlled, either as an ordinary application or as a Windows service that starts with the system. UltraVNC Viewer runs on the controlling computer and connects to the server by address and port. The server listens on port 5900 by default.
Because UltraVNC follows the RFB protocol, it works with other VNC software such as RealVNC and TightVNC. The server can also provide a Java viewer over HTTP, so the remote desktop opens in a web browser on systems without the viewer.
Who may connect
UltraVNC Server offers three ways to check the person on the other end:
- VNC password: a single password stored on the server, limited to eight characters for compatibility with other VNC software.
- MS-Logon I: users sign in with a Windows account from the server’s own domain or machine, and access is granted to selected users and groups.
- MS-Logon II: extends this to accounts in other trusted domains, nested groups and email-style user names.
With the Windows account methods, each user or group gets either full control, which allows mouse and keyboard input, or view-only access.
The server can also ask the local user to accept or refuse each incoming connection, with a timeout and a default answer if nobody responds. Administrators decide what happens when the last viewer disconnects: nothing, locking the workstation or logging the user off.
Encryption plugins
A plain VNC connection is not encrypted. UltraVNC adds encryption through DSM (Data Stream Modification) plugins, such as SecureVNC, that are loaded on both the server and the viewer. Once active, the plugin encrypts the screen data and input travelling between them and allows longer passwords.
Session controls
The viewer can run full screen, scale the remote desktop to fit, and switch to view-only mode. Quick presets for LAN, medium, modem and slow links are available. For finer control, the viewer picks encodings such as Tight, Zlib or the UltraVNC-specific Ultra encoding. Compression and JPEG quality are adjustable, and reduced or grey-scale colors are available for slow connections.
On the server side, UltraVNC can share only a single named window instead of the whole desktop. It can also remove the wallpaper for viewers to cut traffic. For presentations, local keyboard and mouse input can be disabled. For privacy during support work, the viewer can request that the remote monitor be blanked. Several viewers can watch the same server at once, or the server can be set to keep only the first or the newest connection.
Files and chat
UltraVNC’s file transfer window sends files and complete folders in both directions between viewer and server. UltraVNC compresses files before transfer, using less bandwidth than a raw copy. A built-in text chat runs over the same connection and can be opened at any point in the session. Minimizing it keeps the conversation, while closing it erases the text.
Reverse connections and the repeater
Firewalls and routers often block connections to the computer that needs help. UltraVNC can reverse the direction: the viewer waits in listen mode, and the server is told to connect out to it. The server can optionally reconnect automatically if the link drops.
UltraVNC Repeater, a separate component, relays sessions when neither side can accept connections directly. In one mode it lets several servers be reached through a single forwarded port. In the other it acts as a go-between. Each server is registered under a numeric ID of up to nine digits that the viewer uses to find it.
Single Click for help desks
UltraVNC Single Click (SC) is a small, preconfigured server that a customer downloads and runs without installing anything. A text file called helpdesk.txt defines the menu the customer sees. It contains one entry per technician or office with the address of the waiting viewer or repeater and an optional encryption plugin. It also defines window text and status messages. The customer picks an entry, and SC connects out to the technician’s listening viewer. With a single entry SC can start the connection immediately, skipping the menu.
