Compuse Vnc

Driving a remote machine over VNC (compuse-vnc)

Drive a target's screen over plain VNC/RFB with the vnc-remote-control CLI: type text, press named keys, click, screenshot, and OCR. It is a pure client - nothing runs on the target, no agent, no service, no open port, nothing in its process list. The control happens entirely through a VNC/RFB server the target already exposes.

When to use

• A target with no network. A Proxmox/hypervisor VM that is not on the network yet (or never will be) is still driveable through its VNC console - the same screen as the web UI. Ideal for first-boot setup where you configure networking before the guest can reach anything.
• No footprint wanted. Operate a machine with nothing installed or visible on it.
• VNC is the only door. Remote admin where VNC is the one reachable interface.
• Legacy GUI software with no API/CLI/accessibility tree - only a window. Read it with OCR, click by label. Legacy UIs rarely move, so coordinates stay stable.
• Old TUI programs that you operate purely by keypresses (type + key); the target needs only a VNC server, which Proxmox provides out of the box.

Step 0: install the tool, then use it (on YOUR control box only, never the target)

This skill installs vnc-remote-control and then drives it. First make sure the CLI and tesseract are present on the machine you drive FROM (never on the target):

# the CLI - persistent on PATH via uv; skip if already installed
command -v vnc-remote-control >/dev/null || uv tool install vnc-remote-control
# tesseract is a REQUIRED system dependency (OCR is how you find what to click)
command -v tesseract >/dev/null || sudo apt-get install -y tesseract-ocr   # macOS: brew install tesseract | Windows: choco install tesseract

For a one-off without a persistent install, uvx vnc-remote-control ... runs it on demand (uv fetches it each run); tesseract is still required. Then drive the target with the commands below.

Commands

Every command needs --port; --host defaults to 127.0.0.1.

vnc-remote-control --port 5901 screenshot /tmp/g.png --grid 50
vnc-remote-control --host 10.0.0.5 --port 5901 click-text "Next"
vnc-remote-control --port 5901 type "chkdsk c: /f" --enter

The driving loop (how to click the right pixel every time)

RFB pointer coordinates are absolute framebuffer pixels - the same pixels as a native-resolution screenshot. This tool never scales, so a coordinate read off the screenshot is the exact click coordinate. (Past "wrong pixel" failures came from reading coordinates off a scaled image.)

1. Capture and look. screenshot out.png - view it at NATIVE size (do not let the viewer downscale).
2. Read coordinates directly off out.png - there is no scale factor to undo.
3. Verify before committing: screenshot out.png --mark X,Y and check the crosshair lands on target (--grid 50 adds a ruler).
4. Prefer clicking by label over guessing pixels: ocr --grep "Sign in" then click <cx> <cy>, or one-shot click-text "Sign in". click-text only sees text OCR can read - low-contrast or placeholder hints (a faint greyed-out search box), icons, and untitled controls are missed and it fails; fall back to reading the pixel off the screenshot and click X Y.
5. Focus, then type. A freshly opened window/field often does NOT have keyboard focus. Click into the text field first, THEN type. Skipping the click is the #1 reason typed text seems to vanish.

Gotchas

• Focus before typing (see step 5). If text vanishes: screenshot, click the field, type again.
• Keyboard layout is server-side, not yours. You pass the text you want; the client puts each character's Unicode code point on the wire as its keysym (like any VNC client). Your own laptop layout is irrelevant. A layout-aware server (openvmm; on Proxmox the ovm shim derives it from the VM's keyboard: key) maps keysyms to the guest layout. If wrong characters land, the SERVER layout is misconfigured - fix it there, never compensate per keystroke on the client.
• Sluggish guests drop fast input. Slow it down: --delay-scale 2 multiplies every delay, or set individual gaps via --set vnc.key_up_gap=0.2 (keys: key_down_hold, key_up_gap, click_move_gap, click_hold, click_release_gap).
• Nothing happened, or an error? READ the screen before re-sending input - ROOT-CAUSE it. When a click/keystroke seems to have no effect or the flow stops, screenshot + ocr FIRST and act on what the screen ACTUALLY says (an error dialog, a validation message, a progress indicator, a greyed-out or relabeled button). Never blind-retry: if the first click DID land, the same coordinates may now hit a DIFFERENT control (re-firing an installer, dismissing an unread error), and on a laggy guest an "unchanged" screenshot is weak evidence. Only when two screenshots a few seconds apart show a genuinely identical, idle screen is "dropped input" the diagnosis - then retry ONCE with increased delays and re-read the screen.
• A VNC console is a flaky external resource - it can freeze, drop, or lag mid-session. Verify the screen state before acting on it, retry under a timeout, and never assume a keystroke landed. For the self-healing patterns, see bitranox:coding-resilience.

Authentication

• None security (an openvmm/hypervisor console on localhost - the typical Proxmox case) needs nothing.
• VNC password: pass it via the VNC_REMOTE_CONTROL_PASSWORD env var (which --password reads by default), NOT on the command line - a password in argv is visible in ps. TLS/VeNCrypt and Apple Remote Desktop auth are not supported. (demand gated)

VNC_REMOTE_CONTROL_PASSWORD=secret vnc-remote-control --port 5901 key enter

Proxmox / no-network VMs

The VM's console is a VNC/RFB server on the host. Reach it directly, or SSH-tunnel to the console port with ssh -N -L <local-port>:127.0.0.1:<console-port> <user>@<host>, then point the client at 127.0.0.1:<local-port> (-N because no remote command is wanted, and binding the forward to the host's loopback keeps the console off its network). openvmm is the ideal layout-aware target so arbitrary characters and non-US layouts type reliably; plainer VNC servers still work for any text a fixed (usually US) layout can produce.