Remote Desktop (VNC)

MikoVnc (in Miko.Components) is a VNC client: the remote screen fills the component, and a toolbar floats over its top edge. It works with the usual servers (TightVNC, TigerVNC, RealVNC, UltraVNC, x11vnc, libvncserver, macOS Screen Sharing with a VNC password) on every Miko platform. The protocol is managed code, with no native library and no NuGet dependency.

• Toolbar: desktop name, resolution and bitrate. Buttons for the soft keyboard (phones), the keys bar, zoom out / in, settings, fullscreen, disconnect, and collapse. Collapsed, it leaves a small tab at the top edge.
• Keys bar: the keys a phone keyboard lacks: Esc, Tab, Ctrl / Alt / Shift / Win (they latch until the next key), arrows, Del, Home / End, PgUp / PgDn, Ctrl+Alt+Del and F1–F12.
• Settings: picture quality (lossless, high, balanced, low), fit or 1:1, view only, refresh.
• Password: when the server needs one and Password is not set, a dialog asks for it. A wrong password asks again, with the reason.
• No host: without Host the component shows a connect form (address, password, quality).

Setup

No service registration is needed: reference Miko.Components and place the component.

@using Miko.Components.Vnc

<MikoVnc Host="192.168.1.20" Texts="@VncTexts.Chinese" Style="@(new Style { Width = Length.Percent(100), Height = Length.Percent(100) })" />

Port defaults to 5900; display n is port 5900 + n. The connect form and VncAddress.TryParse accept host, host:display, host::port and [ipv6]:port.

On phones, register the native services so that fullscreen can turn the device to landscape and hide the system bars, and so a held touch gives haptic feedback:

builder.UseAndroidNative();   // iOS: UseIosNative(); desktop: UseDesktopNative()

An Android activity should declare WindowSoftInputMode = SoftInput.AdjustResize and ConfigurationChanges (orientation, screen size, keyboard) so that the keyboard and rotation do not recreate it. iOS needs NSLocalNetworkUsageDescription in Info.plist for servers on the LAN.

Input

Input	On the remote desktop
Mouse	One to one: left, middle and right buttons, the wheel (each notch is a button 4 / 5 click; horizontal 6 / 7).
Touch tap	Left click where the finger is. Two taps make a double click.
Touch hold (½ s)	Right click, released where it was held (a ring shows the hold).
Hold, then drag	Left-button drag from where the finger went down (select text, move windows).
Drag	Pans the picture when zoomed in. When the whole screen fits, it scrolls (the wheel).
Keyboard	Keys and typed text go to the remote screen while it has focus. Click it (desktop), or use the keyboard button (phones).

The text a key types is sent as typed, so the local layout applies, and so do dead keys and the IME (Chinese input arrives as Unicode keysyms). Shortcuts are sent by key: with Ctrl, Alt or ⌘ / Win held, the key goes out under its US-layout name, so Ctrl+C is Control + c on every layout. On the desktop, Escape goes to the remote side even in fullscreen; leave fullscreen with the toolbar button.

The remote pointer is drawn locally at the mouse or finger position, in the shape the server sends. With a mouse the system cursor is hidden over the screen (cursor: none), so there is no lag and only one cursor.

The core events this relies on can be used by any component: right / middle buttons reach OnPointerDown / OnPointerUp with Button set, and they never produce a click. OnWheel (@onwheel) can PreventDefault() the scroll. OnKeyUp (@onkeyup) and KeyboardEventArgs.Code give the physical key. A pointerdown handler that calls PreventDefault() keeps focus where it is, as in a browser.

Parameters

Parameter	Type	Default
Host	string?	null	Server host or IP. null shows the connect form. Changing it reconnects.
Port	int	5900	TCP port.
Password	string?	null	The VNC password. When null, the dialog asks if the server needs one.
AutoConnect	bool	true	Connect when shown; otherwise a button waits.
ViewOnly	bool	false	Watch without sending input (ViewOnlyChanged).
Quality	VncQuality	High	Lossless, High, Balanced, Low; the settings change it live (QualityChanged).
Scaling	VncScaling	Fit	Fit (the whole screen) or Actual (1:1, following the pointer).
Shared	bool	true	Let other viewers stay connected.
ShowToolbar	bool	true
Texts	VncTexts	English	VncTexts.Chinese is built in; with { … } changes single texts.
Connected	EventCallback<VncDesktopInfo>		Name, size, protocol and security of the remote desktop.
Disconnected	EventCallback<Exception?>		The failure, or null when the session ended cleanly.
ClipboardReceived	EventCallback<string>		Text the remote side copied.
Error	EventCallback<Exception>		Connection and protocol failures (also shown in the view).
Class, Style			On the root. The component fills its parent.

Methods (UI thread): Connect(), Connect(host, port, password), Disconnect(), SendText(text), SendKeys(keysyms…) (pressed in order, released in reverse, e.g. SendKeys(VncKeys.ControlLeft, 'c')), SendCtrlAltDel(), SendClipboard(text), SetQuality(…), SetViewOnly(…), ZoomIn(), ZoomOut(), FitToScreen(), ActualSize(), ToggleFullscreen(), ToggleKeyboard(), RefreshScreen(). State: State (Idle, Connecting, Authenticating, Connected, Disconnected), ErrorMessage, Desktop, Framebuffer, Client, CurrentQuality, IsViewOnly, IsFullscreen, IsKeyboardActive, Zoom, BytesPerSecond.

Clipboard

The component does not touch the device clipboard by itself. Connect the two directions with Miko.Native's IClipboardService:

<MikoVnc @ref="_vnc" Host="…" ClipboardReceived="@(text => Clipboard.WriteAsync(new() { String = text }))" />

@code {
    [Inject] IClipboardService Clipboard { get; set; } = null!;
    private MikoVnc? _vnc;

    private async Task PasteToRemote() => _vnc!.SendClipboard((await Clipboard.ReadAsync()).Value);
}

Standard RFB clipboard text is Latin-1. Characters outside Latin-1 become ? (type them with SendText instead).

Protocol

	Supported
Versions	RFB 3.3, 3.7, 3.8 (3.889 and 4.x servers speak 3.8)
Security	None, VNC authentication (DES challenge), Tight (with None / VNC inside)
Encodings	Raw, CopyRect, RRE, Hextile, Zlib, ZRLE, Tight (fill, copy / palette / gradient filters, JPEG)
Pseudo-encodings	Cursor (the pointer shape), DesktopSize, ExtendedDesktopSize, LastRect, DesktopName, compression and JPEG quality levels
Pixel format	32-bit true colour, requested from the server whatever its own

Quality picks the encodings: Lossless prefers ZRLE and never asks for JPEG. The other levels prefer Tight, with JPEG for photographic areas (quality 8, 6 and 3) and more compression as they go down. Tight's JPEG is decoded by the engine's image decoder. zlib (Zlib, ZRLE and Tight's four streams) and DES are managed implementations, the same on every platform.

VNC authentication is not encryption: the password challenge is DES, and the session is plain TCP. Use it on a trusted network, or tunnel it (SSH, VPN). VeNCrypt / TLS, RealVNC's RA2 and Apple's Diffie-Hellman security are not supported; a server that offers only those is reported by name.

Without the view

VncClient is public, for tools and tests:

using var client = await VncClient.ConnectAsync(new VncConnectOptions("192.168.1.20") { Password = "…" });
client.FramebufferUpdated += () => { /* client.Framebuffer.Pixels: B, G, R, X rows */ };
client.Start();
client.SendPointer(100, 100, buttons: 1);
client.SendKey(VncKeys.Return, down: true);
client.SendKey(VncKeys.Return, down: false);

Events are raised on the connection's receive thread. Input methods never block, and pointer moves with the same buttons coalesce.

Limitations

• Only one finger is tracked, so there is no pinch zoom or two-finger scroll. Zoom with the toolbar, and scroll by dragging a picture that fits.
• A Windows server's lock screen turns its display off after a while, and many servers then capture a black screen. Moving the pointer (any touch or mouse move) wakes it.
• On Windows keyboards, AltGr arrives as Ctrl+Alt, so AltGr characters are sent as shortcuts. Type them through SendText, or use the remote side's layout.
• iOS hardware keyboards type text, but their arrows and modifiers do not reach the view yet.