[socket] Implement working ready() for LWIP raw TCP sockets (ESP8266/RP2040)

Previously ready() always returned true on ESP8266/RP2040, causing
every socket to be checked on every loop iteration even when no data
was available.

Override ready() in LWIPRawImpl to check rx_buf_/rx_closed_/pcb_ state,
and in LWIPRawListenImpl to check accepted_socket_count_. This uses
existing fields so no extra memory is needed per socket.

Keep ready() virtual only on the non-select path (ESP8266/RP2040) so
the select()-based path (ESP32) retains the non-virtual optimization
from the previous commit.

esphome/components/socket/bsd_sockets_impl.cpp

@@ -16,19 +16,13 @@ namespace esphome::socket {
 
 class BSDSocketImpl final : public Socket {
  public:
-  BSDSocketImpl(int fd, bool monitor_loop = false) : fd_(fd) {
-#ifdef USE_SOCKET_SELECT_SUPPORT
+  BSDSocketImpl(int fd, bool monitor_loop = false) {
+    this->fd_ = fd;
     // Register new socket with the application for select() if monitoring requested
     if (monitor_loop && this->fd_ >= 0) {
       // Only set loop_monitored_ to true if registration succeeds
       this->loop_monitored_ = App.register_socket_fd(this->fd_);
-    } else {
-      this->loop_monitored_ = false;
     }
-#else
-    // Without select support, ignore monitor_loop parameter
-    (void) monitor_loop;
-#endif
   }
   ~BSDSocketImpl() override {
     if (!this->closed_) {
@@ -52,12 +46,10 @@ class BSDSocketImpl final : public Socket {
   int bind(const struct sockaddr *addr, socklen_t addrlen) override { return ::bind(this->fd_, addr, addrlen); }
   int close() override {
     if (!this->closed_) {
-#ifdef USE_SOCKET_SELECT_SUPPORT
       // Unregister from select() before closing if monitored
       if (this->loop_monitored_) {
         App.unregister_socket_fd(this->fd_);
       }
-#endif
       int ret = ::close(this->fd_);
       this->closed_ = true;
       return ret;
@@ -130,23 +122,6 @@ class BSDSocketImpl final : public Socket {
     ::fcntl(this->fd_, F_SETFL, fl);
     return 0;
   }
-
-  int get_fd() const override { return this->fd_; }
-
-#ifdef USE_SOCKET_SELECT_SUPPORT
-  bool ready() const override {
-    if (!this->loop_monitored_)
-      return true;
-    return App.is_socket_ready(this->fd_);
-  }
-#endif
-
- protected:
-  int fd_;
-  bool closed_{false};
-#ifdef USE_SOCKET_SELECT_SUPPORT
-  bool loop_monitored_{false};
-#endif
 };
 
 // Helper to create a socket with optional monitoring

esphome/components/socket/lwip_raw_tcp_impl.cpp

@@ -452,6 +452,8 @@ class LWIPRawImpl : public Socket {
     errno = ENOSYS;
     return -1;
   }
+  bool ready() const override { return this->rx_buf_ != nullptr || this->rx_closed_ || this->pcb_ == nullptr; }
+
   int setblocking(bool blocking) final {
     if (pcb_ == nullptr) {
       errno = ECONNRESET;
@@ -576,6 +578,8 @@ class LWIPRawListenImpl final : public LWIPRawImpl {
     tcp_err(pcb_, LWIPRawImpl::s_err_fn);  // Use base class error handler
   }
 
+  bool ready() const override { return this->accepted_socket_count_ > 0; }
+
   std::unique_ptr<Socket> accept(struct sockaddr *addr, socklen_t *addrlen) override {
     if (pcb_ == nullptr) {
       errno = EBADF;

esphome/components/socket/lwip_sockets_impl.cpp

@@ -11,19 +11,13 @@ namespace esphome::socket {
 
 class LwIPSocketImpl final : public Socket {
  public:
-  LwIPSocketImpl(int fd, bool monitor_loop = false) : fd_(fd) {
-#ifdef USE_SOCKET_SELECT_SUPPORT
+  LwIPSocketImpl(int fd, bool monitor_loop = false) {
+    this->fd_ = fd;
     // Register new socket with the application for select() if monitoring requested
     if (monitor_loop && this->fd_ >= 0) {
       // Only set loop_monitored_ to true if registration succeeds
       this->loop_monitored_ = App.register_socket_fd(this->fd_);
-    } else {
-      this->loop_monitored_ = false;
     }
-#else
-    // Without select support, ignore monitor_loop parameter
-    (void) monitor_loop;
-#endif
   }
   ~LwIPSocketImpl() override {
     if (!this->closed_) {
@@ -49,12 +43,10 @@ class LwIPSocketImpl final : public Socket {
   int bind(const struct sockaddr *addr, socklen_t addrlen) override { return lwip_bind(this->fd_, addr, addrlen); }
   int close() override {
     if (!this->closed_) {
-#ifdef USE_SOCKET_SELECT_SUPPORT
       // Unregister from select() before closing if monitored
       if (this->loop_monitored_) {
         App.unregister_socket_fd(this->fd_);
       }
-#endif
       int ret = lwip_close(this->fd_);
       this->closed_ = true;
       return ret;
@@ -97,23 +89,6 @@ class LwIPSocketImpl final : public Socket {
     lwip_fcntl(this->fd_, F_SETFL, fl);
     return 0;
   }
-
-  int get_fd() const override { return this->fd_; }
-
-#ifdef USE_SOCKET_SELECT_SUPPORT
-  bool ready() const override {
-    if (!this->loop_monitored_)
-      return true;
-    return App.is_socket_ready(this->fd_);
-  }
-#endif
-
- protected:
-  int fd_;
-  bool closed_{false};
-#ifdef USE_SOCKET_SELECT_SUPPORT
-  bool loop_monitored_{false};
-#endif
 };
 
 // Helper to create a socket with optional monitoring

esphome/components/socket/socket.cpp

@@ -10,6 +10,10 @@ namespace esphome::socket {
 
 Socket::~Socket() {}
 
+#ifdef USE_SOCKET_SELECT_SUPPORT
+bool Socket::ready() const { return !this->loop_monitored_ || App.is_socket_ready_(this->fd_); }
+#endif
+
 // Platform-specific inet_ntop wrappers
 #if defined(USE_SOCKET_IMPL_LWIP_TCP)
 // LWIP raw TCP (ESP8266) uses inet_ntoa_r which takes struct by value

esphome/components/socket/socket.h

@@ -63,13 +63,29 @@ class Socket {
   virtual int setblocking(bool blocking) = 0;
   virtual int loop() { return 0; };
 
-  /// Get the underlying file descriptor (returns -1 if not supported)
-  virtual int get_fd() const { return -1; }
+    /// Get the underlying file descriptor (returns -1 if not supported)
+    /// Non-virtual: only one socket implementation is active per build.
+#ifdef USE_SOCKET_SELECT_SUPPORT
+  int get_fd() const { return this->fd_; }
+#else
+  int get_fd() const { return -1; }
+#endif
 
   /// Check if socket has data ready to read
-  /// For loop-monitored sockets, checks with the Application's select() results
-  /// For non-monitored sockets, always returns true (assumes data may be available)
+  /// For select()-based sockets: non-virtual, checks Application's select() results
+  /// For LWIP raw TCP sockets: virtual, checks internal buffer state
+#ifdef USE_SOCKET_SELECT_SUPPORT
+  bool ready() const;
+#else
   virtual bool ready() const { return true; }
+#endif
+
+ protected:
+#ifdef USE_SOCKET_SELECT_SUPPORT
+  int fd_{-1};
+  bool closed_{false};
+  bool loop_monitored_{false};
+#endif
 };
 
 /// Create a socket of the given domain, type and protocol.

esphome/core/application.cpp

@@ -605,15 +605,6 @@ void Application::unregister_socket_fd(int fd) {
   }
 }
 
-bool Application::is_socket_ready(int fd) const {
-  // This function is thread-safe for reading the result of select()
-  // However, it should only be called after select() has been executed in the main loop
-  // The read_fds_ is only modified by select() in the main loop
-  if (fd < 0 || fd >= FD_SETSIZE)
-    return false;
-
-  return FD_ISSET(fd, &this->read_fds_);
-}
 #endif
 
 void Application::yield_with_select_(uint32_t delay_ms) {

esphome/core/application.h

@@ -101,6 +101,10 @@
 #include "esphome/components/update/update_entity.h"
 #endif
 
+namespace esphome::socket {
+class Socket;
+}  // namespace esphome::socket
+
 namespace esphome {
 
 // Teardown timeout constant (in milliseconds)
@@ -491,7 +495,8 @@ class Application {
   void unregister_socket_fd(int fd);
   /// Check if there's data available on a socket without blocking
   /// This function is thread-safe for reading, but should be called after select() has run
-  bool is_socket_ready(int fd) const;
+  /// The read_fds_ is only modified by select() in the main loop
+  bool is_socket_ready(int fd) const { return fd >= 0 && this->is_socket_ready_(fd); }
 
 #ifdef USE_WAKE_LOOP_THREADSAFE
   /// Wake the main event loop from a FreeRTOS task
@@ -503,6 +508,15 @@ class Application {
 
  protected:
   friend Component;
+  friend class socket::Socket;
+
+#ifdef USE_SOCKET_SELECT_SUPPORT
+  /// Fast path for Socket::ready() via friendship - skips negative fd check.
+  /// Safe because: fd was validated in register_socket_fd() at registration time,
+  /// and Socket::ready() only calls this when loop_monitored_ is true (registration succeeded).
+  /// FD_ISSET may include its own upper bounds check depending on platform.
+  bool is_socket_ready_(int fd) const { return FD_ISSET(fd, &this->read_fds_); }
+#endif
 
   void register_component_(Component *comp);