[core] Remove pre-sleep socket scan from fast select path (#15639)

esphome/components/socket/bsd_sockets_impl.cpp

@@ -14,38 +14,34 @@ BSDSocketImpl::BSDSocketImpl(int fd, bool monitor_loop) {
   if (!monitor_loop || this->fd_ < 0)
     return;
 #ifdef USE_LWIP_FAST_SELECT
-  // Cache lwip_sock pointer and register for monitoring (hooks callback internally)
-  this->cached_sock_ = esphome_lwip_get_sock(this->fd_);
-  this->loop_monitored_ = App.register_socket(this->cached_sock_);
+  this->cached_sock_ = hook_fd_for_fast_select(this->fd_);
 #else
   this->loop_monitored_ = App.register_socket_fd(this->fd_);
 #endif
 }
 
-BSDSocketImpl::~BSDSocketImpl() {
-  if (!this->closed_) {
-    this->close();
-  }
-}
+BSDSocketImpl::~BSDSocketImpl() { this->close(); }
 
 int BSDSocketImpl::close() {
-  if (!this->closed_) {
-    // Unregister before closing to avoid dangling pointer in monitored set
-#ifdef USE_LWIP_FAST_SELECT
-    if (this->loop_monitored_) {
-      App.unregister_socket(this->cached_sock_);
-      this->cached_sock_ = nullptr;
-    }
-#else
-    if (this->loop_monitored_) {
-      App.unregister_socket_fd(this->fd_);
-    }
-#endif
-    int ret = ::close(this->fd_);
-    this->closed_ = true;
-    return ret;
+  if (this->fd_ < 0) {
+    // Already closed, or never opened.
+    return 0;
   }
-  return 0;
+#ifdef USE_LWIP_FAST_SELECT
+  // Null the cached lwip_sock pointer before closing. The underlying lwip slot can be
+  // recycled for a new connection as soon as ::close() returns, so anything that might
+  // dereference cached_sock_ post-close (e.g. setsockopt(TCP_NODELAY)) would otherwise
+  // touch an unrelated socket's pcb. No per-socket callback unhook is needed —
+  // all LwIP sockets share the same static event_callback.
+  this->cached_sock_ = nullptr;
+#else
+  if (this->loop_monitored_) {
+    App.unregister_socket_fd(this->fd_);
+  }
+#endif
+  int ret = ::close(this->fd_);
+  this->fd_ = -1;  // Sentinel for "closed" — prevents double-close and makes use-after-close visible.
+  return ret;
 }
 
 int BSDSocketImpl::setblocking(bool blocking) {