feat: replace advert scan with active node discovery in NearbyScreen

NearbyScreen now sends CTL_TYPE_NODE_DISCOVER_REQ (same protocol as the
companion app) instead of a plain self-advert. Nearby repeaters, sensors
and room servers respond with their pub_key and type. Known contacts get
their lastmod refreshed; unknown nodes appear as temporary entries (e.g.
"Repeater") in the list until their advert is received.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

examples/companion_radio/MyMesh.cpp

@@ -764,7 +764,58 @@ bool MyMesh::onContactPathRecv(ContactInfo& contact, uint8_t* in_path, uint8_t i
   return BaseChatMesh::onContactPathRecv(contact, in_path, in_path_len, out_path, out_path_len, extra_type, extra, extra_len);
 }
 
+#define CTL_TYPE_NODE_DISCOVER_REQ  0x80
+#define CTL_TYPE_NODE_DISCOVER_RESP 0x90
+
+void MyMesh::sendNodeDiscoverReq() {
+  uint8_t data[10];
+  data[0] = CTL_TYPE_NODE_DISCOVER_REQ;
+  data[1] = (1 << ADV_TYPE_REPEATER) | (1 << ADV_TYPE_SENSOR) | (1 << ADV_TYPE_ROOM);
+  getRNG()->random(&data[2], 4);
+  memcpy(&_pending_node_discover_tag, &data[2], 4);
+  _pending_node_discover_until = futureMillis(8000);
+  _discovered_count = 0;
+  uint32_t since = 0;
+  memcpy(&data[6], &since, 4);
+  auto pkt = createControlData(data, sizeof(data));
+  if (pkt) sendZeroHop(pkt);
+}
+
+int MyMesh::getDiscoveredNodes(DiscoveredEntry dest[], int max_count) {
+  int n = min(_discovered_count, max_count);
+  memcpy(dest, _discovered, n * sizeof(DiscoveredEntry));
+  return n;
+}
+
 void MyMesh::onControlDataRecv(mesh::Packet *packet) {
+  // handle node discovery responses when in standalone UI mode (no companion app connected)
+  if (!_serial->isBLEConnected() &&
+      (packet->payload[0] & 0xF0) == CTL_TYPE_NODE_DISCOVER_RESP &&
+      packet->payload_len >= 6 + PUB_KEY_SIZE &&
+      _pending_node_discover_tag != 0 &&
+      !millisHasNowPassed(_pending_node_discover_until)) {
+    uint32_t tag;
+    memcpy(&tag, &packet->payload[2], 4);
+    if (tag == _pending_node_discover_tag) {
+      uint8_t node_type = packet->payload[0] & 0x0F;
+      const uint8_t* pub_key = &packet->payload[6];
+      // check if already in contacts — update lastmod so it shows as fresh
+      ContactInfo* known = lookupContactByPubKey(pub_key, PUB_KEY_SIZE);
+      if (known) {
+        known->lastmod = getRTCClock()->getCurrentTime();
+      }
+      // if unknown, add to temporary discovered list
+      if (!known && _discovered_count < DISCOVERED_NODES_MAX) {
+        DiscoveredEntry& e = _discovered[_discovered_count++];
+        memcpy(e.pub_key_prefix, pub_key, 4);
+        e.type = node_type;
+        e.timestamp = getRTCClock()->getCurrentTime();
+      }
+      if (_ui) _ui->notify(UIEventType::newContactMessage);
+    }
+    return;
+  }
+
   if (packet->payload_len + 4 > sizeof(out_frame)) {
     MESH_DEBUG_PRINTLN("onControlDataRecv(), payload_len too long: %d", packet->payload_len);
     return;
@@ -862,6 +913,9 @@ MyMesh::MyMesh(mesh::Radio &radio, mesh::RNG &rng, mesh::RTCClock &rtc, SimpleMe
   dirty_contacts_expiry = 0;
   memset(advert_paths, 0, sizeof(advert_paths));
   memset(send_scope.key, 0, sizeof(send_scope.key));
+  _discovered_count = 0;
+  _pending_node_discover_tag = 0;
+  _pending_node_discover_until = 0;
 
   // defaults
   memset(&_prefs, 0, sizeof(_prefs));

examples/companion_radio/MyMesh.h

@@ -85,6 +85,12 @@ struct AdvertPath {
   uint8_t path[MAX_PATH_SIZE];
 };
 
+struct DiscoveredEntry {
+  uint8_t pub_key_prefix[4];
+  uint8_t type;       // ADV_TYPE_REPEATER / ADV_TYPE_SENSOR / ADV_TYPE_ROOM
+  uint32_t timestamp; // RTC timestamp of discovery
+};
+
 #define EXPECTED_ACK_TABLE_SIZE 8
 
 class MyMesh : public BaseChatMesh, public DataStoreHost {
@@ -101,9 +107,11 @@ public:
   void loop();
   void handleCmdFrame(size_t len);
   bool advert();
+  void sendNodeDiscoverReq();
   void enterCLIRescue();
 
   int  getRecentlyHeard(AdvertPath dest[], int max_num);
+  int  getDiscoveredNodes(DiscoveredEntry dest[], int max_count);
 
 protected:
   float getAirtimeBudgetFactor() const override;
@@ -263,6 +271,12 @@ private:
 
   #define ADVERT_PATH_TABLE_SIZE   16
   AdvertPath advert_paths[ADVERT_PATH_TABLE_SIZE]; // circular table
+
+  #define DISCOVERED_NODES_MAX 8
+  DiscoveredEntry _discovered[DISCOVERED_NODES_MAX];
+  int             _discovered_count;
+  uint32_t        _pending_node_discover_tag;
+  unsigned long   _pending_node_discover_until;
 };
 
 extern MyMesh the_mesh;

examples/companion_radio/ui-new/NearbyScreen.h

@@ -22,8 +22,9 @@ class NearbyScreen : public UIScreen {
     int32_t  lat_e6, lon_e6;
     float    dist_km;
     uint8_t  type;
-    int      contact_idx;
+    int      contact_idx;      // -1 for discovered-but-unknown nodes
-    uint32_t lastmod;   // our RTC timestamp of last received packet
+    uint32_t lastmod;
+    bool     is_discovered;    // true = found via CTL_TYPE_NODE_DISCOVER_RESP, not in contacts[]
   };
 
   static const int MAX_NEARBY = 32;
@@ -101,7 +102,7 @@ class NearbyScreen : public UIScreen {
   }
 
   void startScan() {
-    the_mesh.advert();
+    the_mesh.sendNodeDiscoverReq();
     _scanning = true;
     _scan_started_ms = millis();
   }
@@ -139,6 +140,26 @@ class NearbyScreen : public UIScreen {
       e.type        = ci.type;
       e.contact_idx = i;
       e.lastmod     = ci.lastmod;
+      e.is_discovered = false;
+    }
+
+    // add nodes discovered via CTL_TYPE_NODE_DISCOVER_RESP that are not in contacts[]
+    if (_filter != 0) {  // Fav filter never shows anonymous discovered nodes
+      DiscoveredEntry disc[DISCOVERED_NODES_MAX];
+      int disc_count = the_mesh.getDiscoveredNodes(disc, DISCOVERED_NODES_MAX);
+      for (int i = 0; i < disc_count && _count < MAX_NEARBY; i++) {
+        if (_filter >= 2 && disc[i].type != FILTER_TYPES[_filter]) continue;
+        Entry& e = _entries[_count++];
+        strncpy(e.name, typeName(disc[i].type), sizeof(e.name) - 1);
+        e.name[sizeof(e.name) - 1] = '\0';
+        e.lat_e6  = 0;
+        e.lon_e6  = 0;
+        e.dist_km = -1.0f;
+        e.type    = disc[i].type;
+        e.contact_idx   = -1;
+        e.lastmod       = disc[i].timestamp;
+        e.is_discovered = true;
+      }
     }
 
     // sort by distance ascending; nodes without GPS (-1) go to the end
@@ -242,7 +263,7 @@ public:
     // ── list view ────────────────────────────────────────────────────────────
     display.setColor(DisplayDriver::LIGHT);
     if (_scanning) {
-      display.drawTextCentered(display.width() / 2, 0, "ADVERTISING...");
+      display.drawTextCentered(display.width() / 2, 0, "DISCOVERING...");
     } else {
       char title[22];
       snprintf(title, sizeof(title), "NEARBY[%s]", FILTER_LABELS[_filter]);
@@ -252,7 +273,7 @@ public:
 
     if (_count == 0) {
       display.drawTextCentered(display.width() / 2, 28, _scanning ? "Waiting..." : "No contacts found");
-      display.drawTextCentered(display.width() / 2, 40, "[M]=Advert");
+      display.drawTextCentered(display.width() / 2, 40, "[M]=Discover");
     } else {
       for (int i = 0; i < VISIBLE && (_scroll + i) < _count; i++) {
         int idx = _scroll + i;
@@ -323,7 +344,7 @@ public:
     if (c == KEY_CANCEL) { _task->gotoToolsScreen(); return true; }
     if (c == KEY_CONTEXT_MENU) {
       _ctx_menu.begin("Options", 2);
-      _ctx_menu.addItem("Send my advert");
+      _ctx_menu.addItem("Discover nearby");
       _ctx_menu.addItem("Back");
       return true;
     }