fix: send socket events only from loop()

Every socket event is formatted into one static buffer by one shared
formatter.  setConnected() runs on the WiFi/Ethernet event task and sent
memStatus, wifiStrength and ethernet, then ran sockEmit.loop(), while
loop() could be building its own event.  _safecat() checks the room and
then writes at _len, so another task moving _len in between could write
past the end of g_response.

setConnected() now sends nothing.  loop() broadcasts the status every
STATUS_EMIT_MS (30 s): memStatus, then ethernet, or wifiStrength when it
moved 3 dBm or changed channel.  A client that connects still gets all
of it at once from initClients(), so needsBroadcast and the 1.5 s tick
go, and so does the 1.5 s memStatus for the config panel.

SocketEmitter records loop()'s task in begin().  Off it, beginEmit()
logs and hands out a formatter that writes nothing, and endEmit(),
endEmitRoom() and loop() do nothing.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/ESPNetwork.cpp

@@ -22,8 +22,6 @@ extern ESPNetwork net;
 extern SomfyShadeController somfy;
 extern LoopStats loopStats;
 
-static unsigned long _lastHeapEmit = 0;
-
 static bool _apScanning = false;
 int connectRetries = 0;
 void ESPNetwork::end() {
@@ -144,13 +142,9 @@ void ESPNetwork::loop() {
       }
     }
   }
-  if(millis() - this->lastEmit > 1500) {
-    // Post our connection status if needed.
+  if(millis() - this->lastEmit >= STATUS_EMIT_MS) {
     this->lastEmit = millis();
-    if(this->connected()) {
-      this->emitSockets();
-      this->lastEmit = millis();
-    }
+    if(this->connected()) this->emitSockets();
     resetTaskWdt(); // Make sure we do not reboot here.
   }
   
@@ -176,15 +170,13 @@ bool ESPNetwork::changeAP(const uint8_t *bssid, const int32_t channel) {
   this->connectStart = millis();
   return false;
 }
+// The status broadcast, every STATUS_EMIT_MS from loop().  A wired link goes
+// out every time, the WiFi signal only when it really changed.
 void ESPNetwork::emitSockets() {
   this->emitHeap();
-  if(this->needsBroadcast ||
-    (this->connType == conn_types_t::wifi &&
-      this->rssiBroadcast.due(WiFi.RSSI(), WiFi.channel(), millis(), RSSI_EMIT_MIN_DBM, RSSI_EMIT_MIN_MS))) {
+  if(this->connType != conn_types_t::wifi ||
+    this->rssiBroadcast.due(WiFi.RSSI(), WiFi.channel(), RSSI_EMIT_MIN_DBM))
     this->emitSockets(255);
-    sockEmit.loop();
-    this->needsBroadcast = false;
-  }
 }
 void ESPNetwork::emitSockets(uint8_t num) {
 #if HAS_ETHERNET
@@ -208,7 +200,7 @@ void ESPNetwork::emitSockets(uint8_t num) {
         json->addElem("channel", (int32_t)this->channel);
         json->endObject();
         sockEmit.endEmit(num);
-        this->rssiBroadcast.sent(num == 255, WiFi.RSSI(), WiFi.channel(), millis());
+        this->rssiBroadcast.sent(num == 255, WiFi.RSSI(), WiFi.channel());
       }
       else {
         JsonSockEvent *json = sockEmit.beginEmit("wifiStrength");
@@ -226,12 +218,15 @@ void ESPNetwork::emitSockets(uint8_t num) {
         json->addElem("fullduplex", false);
         json->endObject();
         sockEmit.endEmit(num);
-        this->rssiBroadcast.sent(num == 255, -100, -1, millis());
+        this->rssiBroadcast.sent(num == 255, -100, -1);
       }
   }
   // A broadcast comes from emitSockets(), which has already sent memStatus.
   if(num != 255) this->emitHeap(num);
 }
+// Runs on the WiFi/Ethernet event task, so it sends nothing on the sockets.
+// loop() broadcasts the new status and a client that reconnects gets it from
+// SocketEmitter::initClients().
 void ESPNetwork::setConnected(conn_types_t connType) {
   resetTaskWdt();
   this->connType = connType;
@@ -287,15 +282,6 @@ void ESPNetwork::setConnected(conn_types_t connType) {
         settings.IP.dns1 = ETH.dnsIP(0);
         settings.IP.dns2 = ETH.dnsIP(1);
       }
-      resetTaskWdt();
-      JsonSockEvent *json = sockEmit.beginEmit("ethernet");
-      json->beginObject();
-      json->addElem("connected", this->connected());
-      json->addElem("speed", (uint32_t)ETH.linkSpeed());
-      json->addElem("fullduplex", ETH.fullDuplex());
-      json->endObject();
-      sockEmit.endEmit();
-      resetTaskWdt();
     }
 #endif
   }
@@ -347,9 +333,7 @@ void ESPNetwork::setConnected(conn_types_t connType) {
   }
   else if(SSDP.isStarted) SSDP.end();
   resetTaskWdt();
-  this->emitSockets();
   settings.printAvailHeap();
-  this->needsBroadcast = true;
 }
 #if HAS_ETHERNET
 bool ESPNetwork::connectWired() {
@@ -693,8 +677,6 @@ void ESPNetwork::emitHeap(uint8_t num) {
   uint32_t freeHeap = ESP.getFreeHeap();
   uint32_t maxHeap = ESP.getMaxAllocHeap();
   uint32_t minHeap = ESP.getMinFreeHeap();
-  const heap_emit_t target = heapEmitTarget(num, millis() - _lastHeapEmit, HEAP_EMIT_MS, sockEmit.activeClients(0) > 0);
-  if(target == heap_emit_t::none) return;
   JsonSockEvent *json = sockEmit.beginEmit("memStatus");
   json->beginObject();
   json->addElem("max", maxHeap);
@@ -707,10 +689,6 @@ void ESPNetwork::emitHeap(uint8_t num) {
   json->addElem("loopRate", loopStats.rate(millis()));
   json->addElem("loopMaxUs", loopStats.maxUs());
   json->endObject();
-  if(target == heap_emit_t::room) sockEmit.endEmitRoom(0);
-  else sockEmit.endEmit(num);
-  if(target == heap_emit_t::broadcast) {
-    _lastHeapEmit = millis();
-    loopStats.publish(_lastHeapEmit);
-  }
+  sockEmit.endEmit(num);
+  if(num == 255) loopStats.publish(millis());
 }

src/ESPNetwork.h

@@ -10,12 +10,13 @@
 #define CONNECT_TIMEOUT 20000
 #define SSID_SCAN_INTERVAL 600000
 // A weak signal moves a dBm or two all the time, so only broadcast real
-// changes and not more often than this.
+// changes.
 #define RSSI_EMIT_MIN_DBM 3
-#define RSSI_EMIT_MIN_MS 10000
-// How often memStatus is broadcast.  It is also the one event that is always
-// sent, so it must stay well under Home Assistant's 60s receive timeout.
-#define HEAP_EMIT_MS 30000
+// How often loop() broadcasts the status: memStatus, then wifiStrength or
+// ethernet.  memStatus is the one event that is always sent, so this must stay
+// well under Home Assistant's 60s receive timeout.  A client that connects gets
+// all of it straight away from SocketEmitter::initClients().
+#define STATUS_EMIT_MS 30000
 // A roaming scan only moves to another AP at least this much stronger.
 #define ROAM_MIN_GAIN_DB 6
 class ESPNetwork {
@@ -31,7 +32,6 @@ class ESPNetwork {
     bool wifiFallback = false;
     bool softAPOpened = false;
     bool openingSoftAP = false;
-    bool needsBroadcast = true;
     conn_types_t connType = conn_types_t::unset;
     conn_types_t connTarget = conn_types_t::unset;
     bool connected();

src/JsonFormatter.cpp

@@ -16,6 +16,17 @@ void BufferedJsonFormatter::setBuffer(char *b, size_t sz) {
 size_t BufferedJsonFormatter::length() const {
   return this->_len;
 }
+void JsonFormatter::discard() {
+  // With no room every _safecat() takes the overflow path, and as it has
+  // already overflowed that doesn't log either.
+  this->buff = nullptr;
+  this->buffSize = 0;
+  this->_len = 0;
+  this->_nocomma = true;
+  this->_overflow = true;
+  this->_objects = 0;
+  this->_arrays = 0;
+}
 void JsonFormatter::beginObject(const char *name) {
   if(name && strlen(name) > 0) this->appendElem(name);
   else if(!this->_nocomma) this->_safecat(",");

src/JsonFormatter.h

@@ -24,6 +24,9 @@ class JsonFormatter {
     void _appendNumber(const char *name);
   public:
     bool overflowed() const { return _overflow; }
+    // Drops whatever is written until a buffer is set again.  Nothing is
+    // written anywhere, so tasks can share one discarding formatter.
+    void discard();
     // Writes c as it must appear inside a JSON string (out needs 7 bytes) and
     // returns its length.
     static size_t escapeChar(char c, char *out);

src/Utils.cpp

@@ -130,19 +130,21 @@ int Timestamp::tzOffset() {
   time(&now);
   return Timestamp::calcTZOffset(&now);
 }
-bool rssiNeedsEmit(int rssi, int lastRssi, int channel, int lastChannel, uint32_t sinceLastMs, int minDelta, uint32_t minMs) {
+bool rssiNeedsEmit(int rssi, int lastRssi, int channel, int lastChannel, int minDelta) {
   if(channel != lastChannel) return true;
   int delta = rssi > lastRssi ? rssi - lastRssi : lastRssi - rssi;
-  return delta >= minDelta && sinceLastMs >= minMs;
+  return delta >= minDelta;
 }
-bool RssiBroadcast::due(int rssi, int channel, uint32_t now, int minDelta, uint32_t minMs) const {
-  return rssiNeedsEmit(rssi, this->rssi, channel, this->channel, now - this->at, minDelta, minMs);
+bool RssiBroadcast::due(int rssi, int channel, int minDelta) const {
+  return rssiNeedsEmit(rssi, this->rssi, channel, this->channel, minDelta);
 }
-void RssiBroadcast::sent(bool broadcast, int rssi, int channel, uint32_t now) {
+void RssiBroadcast::sent(bool broadcast, int rssi, int channel) {
   if(!broadcast) return;
   this->rssi = rssi;
   this->channel = channel;
-  this->at = now;
+}
+bool emitAllowed(const void *current, const void *owner) {
+  return owner == nullptr || current == owner;
 }
 bool worthRoaming(bool connected, int currentRssi, int apRssi, int minGain) {
   return !connected || apRssi >= currentRssi + minGain;
@@ -179,11 +181,6 @@ const char *wifiAuthModeName(uint8_t authMode) {
     default: return "UNKNOWN";
   }
 }
-heap_emit_t heapEmitTarget(uint8_t num, uint32_t sinceLastMs, uint32_t intervalMs, bool roomHasClients) {
-  if(num != 255) return heap_emit_t::client;
-  if(sinceLastMs >= intervalMs) return heap_emit_t::broadcast;
-  return roomHasClients ? heap_emit_t::room : heap_emit_t::none;
-}
 void LoopStats::record(uint32_t passUs) {
   _passes++;
   if(passUs > _maxUs) _maxUs = passUs;

src/Utils.h

@@ -58,30 +58,27 @@ struct rebootDelay_t {
   return def;
 }
 // Whether a wifiStrength broadcast is worth sending: always on a channel change,
-// otherwise only for an RSSI change of at least minDelta dBm and not more often
-// than every minMs.
-bool rssiNeedsEmit(int rssi, int lastRssi, int channel, int lastChannel, uint32_t sinceLastMs, int minDelta, uint32_t minMs);
+// otherwise only for an RSSI change of at least minDelta dBm.
+bool rssiNeedsEmit(int rssi, int lastRssi, int channel, int lastChannel, int minDelta);
 // What the last wifiStrength broadcast told every client.  Only broadcasts
 // move it: an emit to one new client tells the others nothing.
 struct RssiBroadcast {
   int rssi = 0;
   int channel = 0;
-  uint32_t at = 0;  // millis() of the last broadcast.
-  bool due(int rssi, int channel, uint32_t now, int minDelta, uint32_t minMs) const;
-  void sent(bool broadcast, int rssi, int channel, uint32_t now);
+  bool due(int rssi, int channel, int minDelta) const;
+  void sent(bool broadcast, int rssi, int channel);
 };
 // Whether an AP a scan found for our SSID is worth connecting to.  While
 // connected it has to be at least minGain dBm stronger than the current AP so
 // a small swing doesn't make the device hop between APs.
 bool worthRoaming(bool connected, int currentRssi, int apRssi, int minGain);
+// Whether the calling task may send socket events.  They are all formatted
+// into one shared buffer, so only loop()'s task may.  owner is that task, or
+// null before SocketEmitter::begin() has recorded it (setup() runs there too).
+bool emitAllowed(const void *current, const void *owner);
 // A short name for a wifi_auth_mode_t value, for the logs.  The values up to
 // WAPI are the same in ESP-IDF 4.4 and 5.x.
 const char *wifiAuthModeName(uint8_t authMode);
-// Who gets a memStatus event.
-enum class heap_emit_t : uint8_t { none, client, broadcast, room };
-// num is the socket client asked for, 255 for everyone.  A broadcast goes out
-// every intervalMs; in between only the clients in room 0 get one.
-heap_emit_t heapEmitTarget(uint8_t num, uint32_t sinceLastMs, uint32_t intervalMs, bool roomHasClients);
 // Whether a firmware the bootloader is holding for verification after an
 // update has proven itself: it has run for minUptimeMs and the network is
 // up.  Until then a reset rolls back to the previous firmware.

src/entryPoints/Web.cpp

@@ -327,7 +327,6 @@ void Web::handleDiscovery(AsyncWebServerRequest *request) {
   if(request->method() == HTTP_POST || request->method() == HTTP_GET) {
     ESP_LOGD(TAG, "Async Discovery Requested");
     sendSnapshot(request, snapshot_doc_t::discovery, 0, discoveryHeader);
-    net.needsBroadcast = true;
   }
   else
     request->send(500, _encoding_text, "Invalid http method");

src/outputs/SocketEmitter.cpp

@@ -8,6 +8,7 @@
 #include "ESPNetwork.h"
 #include "GitOTA.h"
 #include "Timing.h"
+#include "Utils.h"
 
 static const char *TAG = "Sockets";
 
@@ -92,20 +93,36 @@ void SocketEmitter::startup() {
 
 }
 void SocketEmitter::begin() {
+  // Called from setup(), which runs on loop()'s task.
+  this->_owner = xTaskGetCurrentTaskHandle();
   ws.onEvent(SocketEmitter::wsEvent);
   wsServer.addHandler(&ws);
   wsServer.begin();
   ESP_LOGI(TAG, "Socket Server Started...");
 }
+bool SocketEmitter::onLoopTask() const { return emitAllowed(xTaskGetCurrentTaskHandle(), this->_owner); }
 void SocketEmitter::loop() {
+  if(!this->onLoopTask()) {
+    ESP_LOGE(TAG, "Socket loop off loop() from %s, skipped", pcTaskGetName(nullptr));
+    return;
+  }
   ws.cleanupClients();
   this->initClients();
 }
 JsonSockEvent *SocketEmitter::beginEmit(const char *evt) {
+  // Another task would overwrite the event loop() is building in g_response,
+  // and could write past its end.
+  if(!this->onLoopTask()) {
+    ESP_LOGE(TAG, "Socket emit %s off loop() from %s, dropped", evt, pcTaskGetName(nullptr));
+    this->_discard.discard();
+    return &this->_discard;
+  }
   this->json.beginEvent(&ws, evt, g_response, sizeof(g_response));
   return &this->json;
 }
 void SocketEmitter::endEmit(uint8_t num) {
+  // beginEmit() has logged it.
+  if(!this->onLoopTask()) return;
   if(num == 255) {
     this->json.endEvent(0);
   } else {
@@ -115,6 +132,7 @@ void SocketEmitter::endEmit(uint8_t num) {
   resetTaskWdt();
 }
 void SocketEmitter::endEmitRoom(uint8_t room) {
+  if(!this->onLoopTask()) return;
   if(room < SOCK_MAX_ROOMS) {
     room_t *r = &this->rooms[room];
     for(uint8_t i = 0; i < sizeof(r->clients); i++) {

src/outputs/SocketEmitter.h

@@ -22,6 +22,11 @@ class SocketEmitter {
   protected:
     uint8_t newclients = 0;
     uint8_t newClients[5] = {255,255,255,255,255};
+    // loop()'s task, recorded by begin().  Only it may send; see emitAllowed().
+    TaskHandle_t _owner = nullptr;
+    // What beginEmit() hands any other task, so the event goes nowhere.
+    JsonSockEvent _discard;
+    bool onLoopTask() const;
     void delayInit(uint8_t num);
   public:
     JsonSockEvent json;