tools: beacon fixes — cleartext, multi-device, validated-net POST, status URL

Debugging against a real restricted LAN surfaced three fixes:
- Android blocks app cleartext HTTP by default (targetSdk 36) — the port
  discovery + reachability were fine (phone curl reached fmr), only the
  app POST was denied. Added usesCleartextTraffic for this dev tool.
- Multi-device: report + receiver are keyed by device (Build.MODEL) so a
  phone and tablet don't clobber each other; connector connects each.
- POST over a VALIDATED internet network (prefer cellular) since the
  wireless-debug wifi is often a restricted LAN.
- Status/notification now show the target beacon URL + which network, per
  the request to surface what it's connecting to.
Verified live: beacon tracks the (frequently rotating) port via mDNS and
self-reports the current endpoint within seconds.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tools/adb-beacon/receiver.py

@@ -2,15 +2,15 @@
 # SPDX-FileCopyrightText: 2026 Echolot contributors
 # SPDX-License-Identifier: GPL-3.0-or-later
 #
-# Tiny rendezvous receiver for the wireless-adb beacon. The phone POSTs its
-# current wireless-debug endpoint here; the PC-side connector reads the stored
-# file (over SSH) and runs `adb connect`. Dev tooling — not part of the product.
+# Rendezvous receiver for the wireless-adb beacon (dev tool). Phones/tablets
+# POST their current wireless-debug endpoint here, keyed by device; the PC-side
+# connector reads them all and keeps `adb connect` current for each.
 #
-#   POST /beacon  { "ip": "...", "port": N }   header: X-Beacon-Secret: <secret>
-#   GET  /beacon  -> the last stored JSON (no secret; it's just an ip:port)
+#   POST /beacon  { "device": "...", "ip": "...", "port": N }
+#                 header: X-Beacon-Secret: <secret>
+#   GET  /beacon  -> { "<device>": {ip, port, seen_at}, ... }
 #
-# Secret comes from ECHOLOT_BEACON_SECRET; stored state goes to STATE_PATH.
-# Bind is 0.0.0.0:9099 so the phone can reach it over the internet/VPN.
+# ECHOLOT_BEACON_SECRET gates POST; STATE_PATH holds the device map.
 
 import json
 import os
@@ -23,6 +23,22 @@ BIND = os.environ.get("BEACON_BIND", "0.0.0.0")
 PORT = int(os.environ.get("BEACON_PORT", "9099"))
 
 
+def load():
+    try:
+        with open(STATE_PATH) as f:
+            d = json.load(f)
+            return d if isinstance(d, dict) else {}
+    except Exception:
+        return {}
+
+
+def store(d):
+    tmp = STATE_PATH + ".tmp"
+    with open(tmp, "w") as f:
+        json.dump(d, f)
+    os.replace(tmp, STATE_PATH)
+
+
 class Handler(BaseHTTPRequestHandler):
     def _send(self, code, body=b"", ctype="application/json"):
         self.send_response(code)
@@ -35,11 +51,7 @@ class Handler(BaseHTTPRequestHandler):
     def do_GET(self):
         if self.path.rstrip("/") != "/beacon":
             return self._send(404, b'{"error":"not found"}')
-        try:
-            with open(STATE_PATH, "rb") as f:
-                self._send(200, f.read())
-        except FileNotFoundError:
-            self._send(200, b'{"available":false}')
+        self._send(200, json.dumps(load()).encode())
 
     def do_POST(self):
         if self.path.rstrip("/") != "/beacon":
@@ -49,19 +61,18 @@ class Handler(BaseHTTPRequestHandler):
         n = int(self.headers.get("Content-Length", "0"))
         try:
             data = json.loads(self.rfile.read(n) or b"{}")
+            device = str(data.get("device", "default"))
             ip = str(data["ip"])
             port = int(data["port"])
         except Exception:
-            return self._send(400, b'{"error":"need {ip, port}"}')
-        record = {"ip": ip, "port": port, "seen_at": int(time.time())}
-        tmp = STATE_PATH + ".tmp"
-        with open(tmp, "w") as f:
-            json.dump(record, f)
-        os.replace(tmp, STATE_PATH)
-        self._send(200, json.dumps(record).encode())
+            return self._send(400, b'{"error":"need {device, ip, port}"}')
+        d = load()
+        d[device] = {"ip": ip, "port": port, "seen_at": int(time.time())}
+        store(d)
+        self._send(200, json.dumps(d[device]).encode())
 
     def log_message(self, *_):
-        pass  # quiet
+        pass
 
 
 if __name__ == "__main__":