uv-k5-v3-emulator/tools/webui.py

#!/usr/bin/env python3
"""Web remote control for the UV-K5 emulator.

Serves the LCD as a live stream and maps on-screen buttons to the keypad model,
so the emulated radio can be driven from a browser.

Start the emulator first (tools/run.sh), then:

    python3 tools/webui.py --frame-addr 0x200013DC --status-addr 0x2000175C

Then open http://127.0.0.1:8080/

Two things worth knowing:

  * The QMP socket takes a single client, so tools/key.py cannot talk to the same
    emulator while this server is running.
  * There is no authentication. It binds loopback and anyone who reaches the port
    has full control of the emulated radio. Do not expose it.
"""
import argparse
import json
import os
import time

from flask import Flask, Response, jsonify, request

from uvk5_keys import KEYS, is_valid, normalise
from uvk5_logs import LogBuffer
from uvk5_stream import FramePump

KEYPAD_PATH = "/machine/keypad"

# Firmware thresholds, from App/misc.c:
#   key_debounce_10ms     = 2  -> 20 ms to register a press
#   key_repeat_delay_10ms = 40 -> 400 ms counts as HELD, a different event
#
# This is a property of the firmware, not a tunable. Keep it separate from the UI's
# own hold threshold below.
FIRMWARE_HELD_MS = 400
#
# The browser sends the duration it wants and the server holds the key for exactly
# that long. It must not be reproduced by sending `down` and `up` as two requests:
# over a slow link the round trip between them *becomes* the press duration.
# Measured against this server at 400 ms RTT, an intended tap arrived as a 407 ms
# hold, so every short press was dispatched as a held key and handlers like
# MAIN_Key_MENU did nothing. Jitter either side of the threshold is what made it
# look intermittent rather than simply broken.
#
# TAP_MS is latency the user pays directly, because the request does not return
# until the hold finishes. So it is measured, not guessed: with 12 trials per
# value, 20 ms registered only 5/12 times while 30 ms was 12/12. The nominal 20 ms
# debounce is not enough on its own -- KEYBOARD_Poll samples each column 8 times
# and wants 2 matching reads, so the real floor sits above it. 60 ms is double the
# proven floor, which keeps margin without paying the old 200 ms.
#
# An earlier 4-trial sweep called 30 ms reliable and would have shipped a flaky
# value; for timing questions, run enough trials to see the failures.
TAP_MS = 60

# A hold longer than this is a stuck key or a typo, not intent.
MAX_HOLD_MS = 5000

# Long-press support under optimistic send.
#
# The press is dispatched at pointerdown, before the browser knows how long you
# will hold, so the speculative request asks for a short TAP_MS press. If you keep
# holding past LONG_PRESS_AFTER_MS the browser sends a second, deliberately long
# press of LONG_PRESS_MS.
#
# LONG_PRESS_AFTER_MS is a UI decision and must NOT be set to the firmware's own
# 400 ms boundary, even though that is where "held" begins. A deliberate click runs
# 100-500 ms, so at 400 ms ordinary clicks sent tap *and* held, and the firmware
# acted on both. Measured against the real firmware:
#   held DOWN  auto-repeated, moving gMenuCursor 3 -> 12 from a single click
#   held MENU  entered the submenu (gIsInSubMenu 0 -> 1)
# which is what "UP/DOWN behaves like another MENU press" turned out to be.
#
# 900 ms is clear of any accidental click while still an obvious deliberate hold.
LONG_PRESS_AFTER_MS = 900

# The long press itself must clear the firmware's 400 ms threshold
# (key_repeat_delay_10ms = 40) or it would land as another tap.
LONG_PRESS_MS = 900

# Lines kept in the browser's log pane. The pane is a fixed-height scroll box, so
# older lines move up out of view; this caps the DOM behind it, which would
# otherwise grow all session even though only a screenful is visible.
MAX_LOG_LINES = 500

BOUNDARY = "uvk5frame"
TARGET_FPS = 15

# Resend the current frame at least this often even when nothing changed.
#
# Sending only on change saves bandwidth but makes a static screen
# indistinguishable from a dead connection, and a client that joined mid-idle
# would sit blank until something moved. Slow rather than stopped.
IDLE_FRAME_INTERVAL_S = 2.0

# Physical layout of the UV-K5 keypad, for the on-screen grid.
KEY_GRID = [
    ["MENU", "UP",   "DOWN", "EXIT"],
    ["1",    "2",    "3",    "STAR"],
    ["4",    "5",    "6",    "0"],
    ["7",    "8",    "9",    "F"],
]
SIDE_KEYS = ["SIDE1", "SIDE2"]

# Keyboard shortcuts -> radio keys.
KEY_BINDINGS = {
    "ArrowUp": "UP", "ArrowDown": "DOWN",
    "Enter": "MENU", "Escape": "EXIT",
    "KeyF": "F", "KeyM": "MENU",
    "BracketLeft": "SIDE1", "BracketRight": "SIDE2",
    "Digit0": "0", "Digit1": "1", "Digit2": "2", "Digit3": "3", "Digit4": "4",
    "Digit5": "5", "Digit6": "6", "Digit7": "7", "Digit8": "8", "Digit9": "9",
}


POWER_ACTIONS = ("on", "off", "reset", "pause", "resume")


def create_app(client, frame_addr: int, status_addr: int, scale: int = 4,
               supervisor=None, log=None):
    app = Flask(__name__)

    if log is None:
        log = LogBuffer()
    app.config["LOG"] = log

    # One background grabber for every client. client may be None: the emulator
    # can be powered off, and the page still has to load.
    pump = FramePump(client, frame_addr, status_addr, fps=TARGET_FPS, scale=scale)
    pump.start()
    app.config["PUMP"] = pump
    app.config["SUPERVISOR"] = supervisor

    def active_client():
        """The live QMP client, or None when the emulator is off.

        The supervisor is authoritative once present: it replaces the client on
        every power cycle, so the one captured at create_app time goes stale.
        """
        if supervisor is not None:
            return supervisor.client()
        return client

    def set_press(value: str):
        target = active_client()
        if target is None:
            raise LookupError("emulator is off")
        target.command("qom-set", path=KEYPAD_PATH, property="press", value=value)

    @app.get("/")
    def index():
        return Response(render_index(scale), mimetype="text/html")

    @app.get("/api/status")
    def api_status():
        target = active_client()
        if target is None:
            return jsonify(powered=False, status="off")
        try:
            info = target.command("query-status")
        except Exception as exc:
            # The emulator can die under us; that is a state to report, not a 500.
            return jsonify(powered=False, status="unreachable", error=str(exc))
        return jsonify(powered=True, **info)

    @app.get("/api/logs")
    def api_logs():
        since = request.args.get("since", type=int, default=0)
        return jsonify(entries=log.entries(since=since), cursor=log.cursor())

    @app.post("/api/power/<action>")
    def api_power(action):
        action = (action or "").strip().lower()
        if action not in POWER_ACTIONS:
            return jsonify(error=f"unknown action {action!r}",
                           valid=list(POWER_ACTIONS)), 400
        if supervisor is None:
            return jsonify(
                error="power control needs a supervisor; this server was "
                      "started without one"), 409
        # Refuse to kill a process we did not start. Reset is fine either way,
        # since system_reset does not end anything.
        if action == "off" and not supervisor.owns_process():
            return jsonify(
                error="this server attached to an emulator it did not start, "
                      "so it will not stop it. Restart without --attach to "
                      "manage the process here."), 409

        {"on": supervisor.power_on,
         "off": supervisor.power_off,
         "reset": supervisor.reset,
         "pause": supervisor.pause,
         "resume": supervisor.resume}[action]()

        # Point the pump at whatever client is live now. rebind(None) blanks the
        # screen, so power off actually goes dark instead of freezing on the last
        # frame.
        pump.rebind(supervisor.client())
        return jsonify(ok=True, action=action, powered=supervisor.is_running())

    @app.post("/api/key")
    def api_key():
        body = request.get_json(silent=True) or {}
        key = normalise(body.get("key", ""))
        action = (body.get("action") or "tap").strip().lower()

        if not is_valid(key):
            # Log refusals too: a silently dropped key is indistinguishable from
            # a dead button in the browser.
            log.add("key", f"{body.get('key')!r} rejected: not a key on this model")
            return jsonify(error=f"unknown key {body.get('key')!r}",
                           valid=list(KEYS)), 400
        if action not in ("down", "up", "tap"):
            return jsonify(error=f"unknown action {action!r}",
                           valid=["down", "up", "tap"]), 400

        hold_raw = body.get("hold_ms")
        if hold_raw is None:
            hold_ms = TAP_MS
        else:
            try:
                hold_ms = int(hold_raw)
            except (TypeError, ValueError):
                return jsonify(
                    error=f"hold_ms must be a number, got {hold_raw!r}"), 400
            if hold_ms < 0:
                return jsonify(error="hold_ms must not be negative"), 400
            hold_ms = min(hold_ms, MAX_HOLD_MS)

        try:
            if action == "down":
                log.add("key", f"{key} down")
                set_press(key)
            elif action == "up":
                log.add("key", f"{key} up")
                set_press("")
            else:
                # Label by what the FIRMWARE will conclude, so the log says what
                # the radio saw. That boundary is 400 ms (key_repeat_delay_10ms),
                # not the UI's hold threshold -- conflating the two is what caused
                # the tap+held double send in the first place.
                kind = "held" if hold_ms >= FIRMWARE_HELD_MS else "tap"
                log.add("key", f"{key} {kind} {hold_ms}ms")
                # Hold here, locally. See the note on TAP_MS: doing this as two
                # requests puts the network round trip inside the press duration.
                set_press(key)
                time.sleep(hold_ms / 1000)
                set_press("")
        except LookupError:
            log.add("key", f"{key} ignored: emulator is off")
            return jsonify(error="emulator is off; press On first"), 409
        return jsonify(ok=True, key=key, action=action, hold_ms=hold_ms)

    @app.post("/api/release-all")
    def api_release_all():
        """Safety valve: an empty press clears every key in the model."""
        try:
            set_press("")
        except LookupError:
            return jsonify(error="emulator is off"), 409
        return jsonify(ok=True)

    def wait_for_frame(timeout: float = 2.0):
        deadline = time.monotonic() + timeout
        while time.monotonic() < deadline:
            png = pump.latest()
            if png is not None:
                return png
            time.sleep(0.02)
        return None

    @app.get("/frame.png")
    def frame_png():
        png = wait_for_frame()
        if png is None:
            return jsonify(error="no frame available; is the emulator on?"), 503
        return Response(png, mimetype="image/png",
                        headers={"Cache-Control": "no-store"})

    @app.get("/stream")
    def stream():
        # limit exists for tests; unset means stream until the client leaves.
        limit = request.args.get("limit", type=int)
        interval = 1.0 / TARGET_FPS

        def frames():
            sent, seen, last_sent_at = 0, -1, 0.0
            while limit is None or sent < limit:
                png = pump.latest()
                generation = pump.generation()
                now = time.monotonic()
                # Send on change, and otherwise at the idle keepalive rate. Change
                # detection alone leaves a static screen looking like a dead
                # connection, and a client joining mid-idle would stay blank.
                stale = now - last_sent_at >= IDLE_FRAME_INTERVAL_S
                if png is not None and (generation != seen or stale
                                        or limit is not None):
                    seen = generation
                    last_sent_at = now
                    yield (b"--" + BOUNDARY.encode() + b"\r\n"
                           b"Content-Type: image/png\r\n"
                           b"Content-Length: " + str(len(png)).encode()
                           + b"\r\n\r\n" + png + b"\r\n")
                    sent += 1
                else:
                    time.sleep(interval)

        return Response(frames(),
                        mimetype=f"multipart/x-mixed-replace; boundary={BOUNDARY}",
                        headers={"Cache-Control": "no-store",
                                 "X-Accel-Buffering": "no"})

    return app


def render_index(scale: int) -> str:
    grid = "\n".join(
        "<div class='row'>" + "".join(
            f'<button class="key" data-key="{k}">{"*" if k == "STAR" else k}</button>'
            for k in row) + "</div>"
        for row in KEY_GRID
    )
    sides = "".join(
        f'<button class="key side" data-key="{k}">{k}</button>' for k in SIDE_KEYS
    )
    return f"""<!doctype html>
<html lang="en"><head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width,initial-scale=1">
<title>UV-K5 remote</title>
<style>
  :root {{ color-scheme: dark; }}
  body {{ margin:0; min-height:100vh; display:grid; place-items:center;
         background:#15171a; color:#c9d1d9;
         font:14px/1.4 ui-monospace,SFMono-Regular,Menlo,monospace; }}
  .radio {{ display:flex; flex-direction:column; align-items:center; gap:14px;
           padding:20px; background:#1e2126; border:1px solid #2d333b;
           border-radius:14px; }}
  /* pixelated keeps the 128x64 LCD crisp when scaled up */
  /* The border lives on .screenwrap so it stays put when the frame is hidden. */
  #screen {{ display:block; image-rendering:pixelated; background:#c8d6b9; }}
  .body {{ display:flex; gap:14px; align-items:flex-start; }}
  .sides {{ display:flex; flex-direction:column; gap:8px; }}
  .pad {{ display:flex; flex-direction:column; gap:8px; }}
  .row {{ display:flex; gap:8px; }}
  .key {{ width:62px; height:44px; font:inherit; font-weight:600; color:#c9d1d9;
         background:#2b3138; border:1px solid #3a424b; border-radius:8px;
         cursor:pointer; user-select:none; -webkit-user-select:none;
         touch-action:manipulation; }}
  .key:hover {{ background:#343b44; }}
  .key.active {{ background:#4b8bf5; border-color:#4b8bf5; color:#fff; }}
  .side {{ width:76px; }}
  .hint {{ color:#6e7681; font-size:12px; text-align:center; max-width:430px; }}
  #status {{ font-size:12px; color:#6e7681; }}
  .powerbar {{ display:flex; gap:8px; align-items:center; align-self:stretch; }}
  .pwr {{ padding:6px 14px; font:inherit; color:#c9d1d9; background:#2b3138;
         border:1px solid #3a424b; border-radius:6px; cursor:pointer; }}
  .pwr:hover:not(:disabled) {{ background:#343b44; }}
  .pwr:disabled {{ opacity:0.5; cursor:default; }}
  #powerstate {{ font-size:12px; color:#6e7681; margin-left:auto; }}
  #powerstate.on {{ color:#3fb950; }}
  /*
   * Powered off is a dark panel, drawn by the wrapper so the frame itself can be
   * hidden. An earlier attempt put a dark background on the <img> alone, which
   * changed nothing visible: the image kept painting the last frame over it, so
   * Off looked like it had not worked.
   */
  .screenwrap {{ background:#0b0d10; border:3px solid #0d1117; border-radius:4px;
                line-height:0; }}
  .screenwrap.screen-off #screen {{ visibility:hidden; }}
  #logpane {{ align-self:stretch; }}
  #logpane summary {{ font-size:12px; color:#6e7681; cursor:pointer;
                     user-select:none; }}
  /*
   * Fixed height, so the box never grows with content: older lines move up out
   * of view and you scroll back to read them. min-height matches height so a
   * nearly empty pane does not jump around as the first lines arrive.
   */
  #logtext {{ height:180px; min-height:180px; overflow-y:auto; margin:6px 0 0;
             padding:8px; background:#0d1117; border:1px solid #2d333b;
             border-radius:6px; white-space:pre-wrap; word-break:break-all;
             font:12px/1.45 ui-monospace,SFMono-Regular,Menlo,monospace;
             color:#8b949e; }}
</style>
</head><body>
<div class="radio">
  <div class="powerbar">
    <button class="pwr" data-power="on">On</button>
    <button class="pwr" data-power="off">Off</button>
    <button class="pwr" data-power="reset">Reset</button>
    <span id="powerstate">-</span>
  </div>
  <div class="screenwrap" id="screenwrap">
    <img id="screen" src="/stream" alt="radio LCD"
         width="{128 * scale}" height="{64 * scale}">
  </div>
  <div class="body">
    <div class="sides">{sides}</div>
    <div class="pad">{grid}</div>
  </div>
  <div id="status">connecting...</div>
  <details id="logpane" open>
    <summary>Logs (firmware serial, qemu, power)</summary>
    <pre id="logtext"></pre>
  </details>
  <p class="hint">Keys are sent the moment you press, so a slow link does not
  add the click duration to the delay. Keep holding past 400 ms for a long press,
  which the firmware treats as a separate event. Arrows move, Enter is MENU,
  Esc is EXIT, digits map straight through. No PTT button -- the keypad model
  has no PTT line.</p>
</div>
<script>
const BINDINGS = {json.dumps(KEY_BINDINGS)};
const TAP_MS = {TAP_MS};
const LONG_PRESS_AFTER_MS = {LONG_PRESS_AFTER_MS};
const LONG_PRESS_MS = {LONG_PRESS_MS};
const pressedAt = new Map();
const longTimers = new Map();

async function sendKey(key, holdMs) {{
  try {{
    await fetch('/api/key', {{
      method: 'POST',
      headers: {{'Content-Type': 'application/json'}},
      body: JSON.stringify({{key: key, hold_ms: Math.round(holdMs)}})
    }});
  }} catch (err) {{
    document.getElementById('status').textContent = 'send failed: ' + err;
  }}
}}

function mark(key, on) {{
  document.querySelectorAll('[data-key="' + key + '"]')
    .forEach(el => el.classList.toggle('active', on));
}}

// Fire at pointerdown, not at release. Latency is the thing worth optimising
// here: waiting for pointerup leaves the network idle for the whole click, which
// on a 400 ms link cost ~120 ms per key for nothing.
//
// The duration is not known yet at this point, so the speculative request asks
// for a short press. Holding past LONG_PRESS_AFTER_MS sends a second, long press,
// which is how held events stay reachable.
//
// The duration still travels as a number rather than as two down/up requests: the
// round trip between those would itself exceed the firmware's 400 ms held
// threshold and turn every tap into a hold.
function down(key) {{
  if (pressedAt.has(key)) return;
  pressedAt.set(key, performance.now());
  mark(key, true);
  sendKey(key, TAP_MS);
  longTimers.set(key, setTimeout(() => {{
    // Still held, so the user meant a long press.
    if (pressedAt.has(key)) sendKey(key, LONG_PRESS_MS);
  }}, LONG_PRESS_AFTER_MS));
}}
function up(key) {{
  if (!pressedAt.has(key)) return;
  pressedAt.delete(key);
  const timer = longTimers.get(key);
  if (timer !== undefined) {{
    clearTimeout(timer);
    longTimers.delete(key);
  }}
  mark(key, false);
}}

document.querySelectorAll('.key').forEach(btn => {{
  const key = btn.dataset.key;
  btn.addEventListener('pointerdown', ev => {{ ev.preventDefault(); down(key); }});
  btn.addEventListener('pointerup', ev => {{ ev.preventDefault(); up(key); }});
  btn.addEventListener('pointerleave', () => up(key));
  btn.addEventListener('pointercancel', () => up(key));
  btn.addEventListener('contextmenu', ev => ev.preventDefault());
}});

addEventListener('keydown', ev => {{
  const key = BINDINGS[ev.code];
  if (!key || ev.repeat) return;
  ev.preventDefault();
  down(key);
}});
addEventListener('keyup', ev => {{
  const key = BINDINGS[ev.code];
  if (!key) return;
  ev.preventDefault();
  up(key);
}});
// Release on blur, so losing focus mid-press cannot leave a key stuck down.
addEventListener('blur', () => {{
  [...pressedAt.keys()].forEach(up);
  fetch('/api/release-all', {{method: 'POST'}}).catch(() => {{}});
}});

document.querySelectorAll('.pwr').forEach(btn => {{
  btn.addEventListener('click', async () => {{
    const action = btn.dataset.power;
    // Off ends the guest. A stray click should not do that silently.
    if (action === 'off' &&
        !confirm('Power off the emulator? Guest state is lost.')) {{
      return;
    }}
    document.querySelectorAll('.pwr').forEach(b => b.disabled = true);
    try {{
      const r = await fetch('/api/power/' + action, {{method: 'POST'}});
      if (!r.ok) {{
        const j = await r.json().catch(() => ({{}}));
        document.getElementById('status').textContent =
          'power ' + action + ' refused: ' + (j.error || r.status);
      }}
    }} catch (err) {{
      document.getElementById('status').textContent = 'power failed: ' + err;
    }} finally {{
      document.querySelectorAll('.pwr').forEach(b => b.disabled = false);
      poll();
      // Restart the stream: the old one ends when the emulator goes away.
      const img = document.getElementById('screen');
      img.src = '/stream?t=' + Date.now();
    }}
  }});
}});

function showPower(powered) {{
  const label = document.getElementById('powerstate');
  label.textContent = powered ? 'on' : 'off';
  label.classList.toggle('on', powered);
  document.getElementById('screenwrap')
    .classList.toggle('screen-off', !powered);
}}

async function poll() {{
  try {{
    const r = await fetch('/api/status');
    const s = await r.json();
    showPower(!!s.powered);
    document.getElementById('status').textContent =
      s.powered ? ('guest: ' + (s.status || 'unknown'))
                : 'powered off -- press On to boot';
  }} catch (err) {{
    showPower(false);
    document.getElementById('status').textContent = 'server unreachable';
  }}
}}
poll();
setInterval(poll, 3000);

// Cap the DOM as well as the server-side buffer. The pane scrolls, but an
// unbounded <pre> would still grow memory over a long session.
const MAX_LOG_LINES = {MAX_LOG_LINES};
let logCursor = 0;

async function pollLogs() {{
  const pre = document.getElementById('logtext');
  try {{
    const r = await fetch('/api/logs?since=' + logCursor);
    const j = await r.json();
    logCursor = j.cursor;
    if (!j.entries.length) return;

    // Only stick to the bottom if the user is already there. Otherwise a new
    // line would yank the view away from whatever they scrolled up to read.
    const atBottom =
      pre.scrollHeight - pre.scrollTop - pre.clientHeight < 24;

    for (const e of j.entries) {{
      pre.textContent += e.time + ' [' + e.source + '] ' + e.text + '\\n';
    }}
    const lines = pre.textContent.split('\\n');
    if (lines.length > MAX_LOG_LINES) {{
      pre.textContent = lines.slice(-MAX_LOG_LINES).join('\\n');
    }}
    if (atBottom) pre.scrollTop = pre.scrollHeight;
  }} catch (err) {{
    /* leave the pane as it is; the next poll will catch up */
  }}
}}
pollLogs();
setInterval(pollLogs, 2000);
</script>
</body></html>"""


def main() -> int:
    ap = argparse.ArgumentParser(description=__doc__.splitlines()[0])
    ap.add_argument("--qmp", default="/tmp/uvk5-qmp.sock")
    ap.add_argument("--frame-addr", type=lambda v: int(v, 0), required=True,
                    help="address of gFrameBuffer (moves between builds)")
    ap.add_argument("--status-addr", type=lambda v: int(v, 0), required=True,
                    help="address of gStatusLine")
    ap.add_argument("--host", default="127.0.0.1")
    ap.add_argument("--port", type=int, default=8080)
    ap.add_argument("--scale", type=int, default=4)
    ap.add_argument("--attach", action="store_true",
                    help="attach to an emulator started elsewhere (run.sh) "
                         "instead of managing one. Off is then refused, since "
                         "this server did not start that process.")
    ap.add_argument("--qemu", default=os.path.expanduser(
        "~/qemu-build/qemu-7.2+dfsg/build/qemu-system-arm"))
    ap.add_argument("--elf", default=os.path.expanduser(
        "~/uvk5-port/uvk5-sat/build/CW/nr7y.cw.elf"))
    ap.add_argument("--flash", default=os.path.join(
        os.path.dirname(os.path.dirname(os.path.abspath(__file__))),
        "assets", "flash.img"))
    ap.add_argument("--gdb-port", type=int, default=1234)
    args = ap.parse_args()

    from uvk5_qmp import QmpClient
    from uvk5_supervisor import Supervisor, default_launcher, wait_for_socket

    def connect():
        if not wait_for_socket(args.qmp, timeout=15):
            raise RuntimeError(f"QMP socket never appeared at {args.qmp}")
        return QmpClient(args.qmp)

    # One buffer shared by the supervisor and the HTTP layer, so power events,
    # QEMU stderr and firmware serial all land in the same place.
    log = LogBuffer()
    supervisor = Supervisor(
        launch=default_launcher(args.qemu, args.flash, args.elf, args.qmp,
                                gdb_port=args.gdb_port),
        connect=connect, log=log)

    if args.attach:
        # Someone else owns the process; adopt it so the screen works, but Off
        # will refuse.
        supervisor.adopt(connect())
    # Otherwise the emulator stays OFF on purpose. The user presses On, so the
    # page behaves like walking up to a machine rather than finding it booted.

    app = create_app(supervisor.client(), args.frame_addr, args.status_addr,
                     args.scale, supervisor=supervisor, log=log)
    print(f"serving on http://{args.host}:{args.port}/")
    print("attached to a running emulator" if args.attach
          else "emulator is OFF; press On in the browser to boot it")
    print("no authentication: anyone who can reach this port controls the radio")
    app.run(host=args.host, port=args.port, threaded=True)
    return 0


if __name__ == "__main__":
    raise SystemExit(main())