Optimize socket operations by checking readiness in the main loop (#8918)

esphome/components/api/api_connection.cpp

@@ -135,31 +135,35 @@ void APIConnection::loop() {
              api_error_to_str(err), errno);
     return;
   }
-  ReadPacketBuffer buffer;
-  err = this->helper_->read_packet(&buffer);
-  if (err == APIError::WOULD_BLOCK) {
-    // pass
-  } else if (err != APIError::OK) {
-    on_fatal_error();
-    if (err == APIError::SOCKET_READ_FAILED && errno == ECONNRESET) {
-      ESP_LOGW(TAG, "%s: Connection reset", this->client_combined_info_.c_str());
-    } else if (err == APIError::CONNECTION_CLOSED) {
-      ESP_LOGW(TAG, "%s: Connection closed", this->client_combined_info_.c_str());
-    } else {
-      ESP_LOGW(TAG, "%s: Reading failed: %s errno=%d", this->client_combined_info_.c_str(), api_error_to_str(err),
-               errno);
-    }
-    return;
-  } else {
-    this->last_traffic_ = App.get_loop_component_start_time();
-    // read a packet
-    if (buffer.data_len > 0) {
-      this->read_message(buffer.data_len, buffer.type, &buffer.container[buffer.data_offset]);
-    } else {
-      this->read_message(0, buffer.type, nullptr);
-    }
-    if (this->remove_)
+
+  // Check if socket has data ready before attempting to read
+  if (this->helper_->is_socket_ready()) {
+    ReadPacketBuffer buffer;
+    err = this->helper_->read_packet(&buffer);
+    if (err == APIError::WOULD_BLOCK) {
+      // pass
+    } else if (err != APIError::OK) {
+      on_fatal_error();
+      if (err == APIError::SOCKET_READ_FAILED && errno == ECONNRESET) {
+        ESP_LOGW(TAG, "%s: Connection reset", this->client_combined_info_.c_str());
+      } else if (err == APIError::CONNECTION_CLOSED) {
+        ESP_LOGW(TAG, "%s: Connection closed", this->client_combined_info_.c_str());
+      } else {
+        ESP_LOGW(TAG, "%s: Reading failed: %s errno=%d", this->client_combined_info_.c_str(), api_error_to_str(err),
+                 errno);
+      }
       return;
+    } else {
+      this->last_traffic_ = App.get_loop_component_start_time();
+      // read a packet
+      if (buffer.data_len > 0) {
+        this->read_message(buffer.data_len, buffer.type, &buffer.container[buffer.data_offset]);
+      } else {
+        this->read_message(0, buffer.type, nullptr);
+      }
+      if (this->remove_)
+        return;
+    }
   }
 
   if (!this->deferred_message_queue_.empty() && this->helper_->can_write_without_blocking()) {

esphome/components/api/api_frame_helper.h

@@ -13,6 +13,7 @@
 
 #include "api_noise_context.h"
 #include "esphome/components/socket/socket.h"
+#include "esphome/core/application.h"
 
 namespace esphome {
 namespace api {
@@ -90,6 +91,8 @@ class APIFrameHelper {
   virtual uint8_t frame_header_padding() = 0;
   // Get the frame footer size required by this protocol
   virtual uint8_t frame_footer_size() = 0;
+  // Check if socket has data ready to read
+  bool is_socket_ready() const { return socket_ != nullptr && socket_->ready(); }
 
  protected:
   // Struct for holding parsed frame data

esphome/components/api/api_server.cpp

@@ -43,7 +43,7 @@ void APIServer::setup() {
   }
 #endif
 
-  this->socket_ = socket::socket_ip(SOCK_STREAM, 0);
+  this->socket_ = socket::socket_ip_loop_monitored(SOCK_STREAM, 0);  // monitored for incoming connections
   if (this->socket_ == nullptr) {
     ESP_LOGW(TAG, "Could not create socket");
     this->mark_failed();
@@ -112,18 +112,20 @@ void APIServer::setup() {
 }
 
 void APIServer::loop() {
-  // Accept new clients
-  while (true) {
-    struct sockaddr_storage source_addr;
-    socklen_t addr_len = sizeof(source_addr);
-    auto sock = this->socket_->accept((struct sockaddr *) &source_addr, &addr_len);
-    if (!sock)
-      break;
-    ESP_LOGD(TAG, "Accepted %s", sock->getpeername().c_str());
+  // Accept new clients only if the socket has incoming connections
+  if (this->socket_->ready()) {
+    while (true) {
+      struct sockaddr_storage source_addr;
+      socklen_t addr_len = sizeof(source_addr);
+      auto sock = this->socket_->accept_loop_monitored((struct sockaddr *) &source_addr, &addr_len);
+      if (!sock)
+        break;
+      ESP_LOGD(TAG, "Accepted %s", sock->getpeername().c_str());
 
-    auto *conn = new APIConnection(std::move(sock), this);
-    this->clients_.emplace_back(conn);
-    conn->start();
+      auto *conn = new APIConnection(std::move(sock), this);
+      this->clients_.emplace_back(conn);
+      conn->start();
+    }
   }
 
   // Process clients and remove disconnected ones in a single pass

esphome/components/esphome/ota/ota_esphome.cpp

@@ -26,7 +26,7 @@ void ESPHomeOTAComponent::setup() {
   ota::register_ota_platform(this);
 #endif
 
-  server_ = socket::socket_ip(SOCK_STREAM, 0);
+  server_ = socket::socket_ip_loop_monitored(SOCK_STREAM, 0);  // monitored for incoming connections
   if (server_ == nullptr) {
     ESP_LOGW(TAG, "Could not create socket");
     this->mark_failed();
@@ -100,9 +100,12 @@ void ESPHomeOTAComponent::handle_() {
 #endif
 
   if (client_ == nullptr) {
-    struct sockaddr_storage source_addr;
-    socklen_t addr_len = sizeof(source_addr);
-    client_ = server_->accept((struct sockaddr *) &source_addr, &addr_len);
+    // Check if the server socket is ready before accepting
+    if (this->server_->ready()) {
+      struct sockaddr_storage source_addr;
+      socklen_t addr_len = sizeof(source_addr);
+      client_ = server_->accept((struct sockaddr *) &source_addr, &addr_len);
+    }
   }
   if (client_ == nullptr)
     return;

esphome/components/socket/__init__.py

@@ -35,5 +35,7 @@ async def to_code(config):
         cg.add_define("USE_SOCKET_IMPL_LWIP_TCP")
     elif impl == IMPLEMENTATION_LWIP_SOCKETS:
         cg.add_define("USE_SOCKET_IMPL_LWIP_SOCKETS")
+        cg.add_define("USE_SOCKET_SELECT_SUPPORT")
     elif impl == IMPLEMENTATION_BSD_SOCKETS:
         cg.add_define("USE_SOCKET_IMPL_BSD_SOCKETS")
+        cg.add_define("USE_SOCKET_SELECT_SUPPORT")

esphome/components/socket/bsd_sockets_impl.cpp

@@ -5,6 +5,7 @@
 #ifdef USE_SOCKET_IMPL_BSD_SOCKETS
 
 #include <cstring>
+#include "esphome/core/application.h"
 
 #ifdef USE_ESP32
 #include <esp_idf_version.h>
@@ -40,7 +41,20 @@ std::string format_sockaddr(const struct sockaddr_storage &storage) {
 
 class BSDSocketImpl : public Socket {
  public:
-  BSDSocketImpl(int fd) : fd_(fd) {}
+  BSDSocketImpl(int fd, bool monitor_loop = false) : fd_(fd) {
+#ifdef USE_SOCKET_SELECT_SUPPORT
+    // Register new socket with the application for select() if monitoring requested
+    if (monitor_loop && fd_ >= 0) {
+      // Only set loop_monitored_ to true if registration succeeds
+      loop_monitored_ = App.register_socket_fd(fd_);
+    } else {
+      loop_monitored_ = false;
+    }
+#else
+    // Without select support, ignore monitor_loop parameter
+    (void) monitor_loop;
+#endif
+  }
   ~BSDSocketImpl() override {
     if (!closed_) {
       close();  // NOLINT(clang-analyzer-optin.cplusplus.VirtualCall)
@@ -48,16 +62,35 @@ class BSDSocketImpl : public Socket {
   }
   int connect(const struct sockaddr *addr, socklen_t addrlen) override { return ::connect(fd_, addr, addrlen); }
   std::unique_ptr<Socket> accept(struct sockaddr *addr, socklen_t *addrlen) override {
+    return accept_impl_(addr, addrlen, false);
+  }
+  std::unique_ptr<Socket> accept_loop_monitored(struct sockaddr *addr, socklen_t *addrlen) override {
+    return accept_impl_(addr, addrlen, true);
+  }
+
+ private:
+  std::unique_ptr<Socket> accept_impl_(struct sockaddr *addr, socklen_t *addrlen, bool loop_monitored) {
     int fd = ::accept(fd_, addr, addrlen);
     if (fd == -1)
       return {};
-    return make_unique<BSDSocketImpl>(fd);
+    return make_unique<BSDSocketImpl>(fd, loop_monitored);
   }
+
+ public:
   int bind(const struct sockaddr *addr, socklen_t addrlen) override { return ::bind(fd_, addr, addrlen); }
   int close() override {
-    int ret = ::close(fd_);
-    closed_ = true;
-    return ret;
+    if (!closed_) {
+#ifdef USE_SOCKET_SELECT_SUPPORT
+      // Unregister from select() before closing if monitored
+      if (loop_monitored_) {
+        App.unregister_socket_fd(fd_);
+      }
+#endif
+      int ret = ::close(fd_);
+      closed_ = true;
+      return ret;
+    }
+    return 0;
   }
   int shutdown(int how) override { return ::shutdown(fd_, how); }
 
@@ -126,16 +159,27 @@ class BSDSocketImpl : public Socket {
     return 0;
   }
 
+  int get_fd() const override { return fd_; }
+
  protected:
   int fd_;
   bool closed_ = false;
 };
 
-std::unique_ptr<Socket> socket(int domain, int type, int protocol) {
+// Helper to create a socket with optional monitoring
+static std::unique_ptr<Socket> create_socket(int domain, int type, int protocol, bool loop_monitored = false) {
   int ret = ::socket(domain, type, protocol);
   if (ret == -1)
     return nullptr;
-  return std::unique_ptr<Socket>{new BSDSocketImpl(ret)};
+  return std::unique_ptr<Socket>{new BSDSocketImpl(ret, loop_monitored)};
+}
+
+std::unique_ptr<Socket> socket(int domain, int type, int protocol) {
+  return create_socket(domain, type, protocol, false);
+}
+
+std::unique_ptr<Socket> socket_loop_monitored(int domain, int type, int protocol) {
+  return create_socket(domain, type, protocol, true);
 }
 
 }  // namespace socket

esphome/components/socket/lwip_raw_tcp_impl.cpp

@@ -606,6 +606,11 @@ std::unique_ptr<Socket> socket(int domain, int type, int protocol) {
   return std::unique_ptr<Socket>{sock};
 }
 
+std::unique_ptr<Socket> socket_loop_monitored(int domain, int type, int protocol) {
+  // LWIPRawImpl doesn't use file descriptors, so monitoring is not applicable
+  return socket(domain, type, protocol);
+}
+
 }  // namespace socket
 }  // namespace esphome
 

esphome/components/socket/lwip_sockets_impl.cpp

@@ -5,6 +5,7 @@
 #ifdef USE_SOCKET_IMPL_LWIP_SOCKETS
 
 #include <cstring>
+#include "esphome/core/application.h"
 
 namespace esphome {
 namespace socket {
@@ -33,7 +34,20 @@ std::string format_sockaddr(const struct sockaddr_storage &storage) {
 
 class LwIPSocketImpl : public Socket {
  public:
-  LwIPSocketImpl(int fd) : fd_(fd) {}
+  LwIPSocketImpl(int fd, bool monitor_loop = false) : fd_(fd) {
+#ifdef USE_SOCKET_SELECT_SUPPORT
+    // Register new socket with the application for select() if monitoring requested
+    if (monitor_loop && fd_ >= 0) {
+      // Only set loop_monitored_ to true if registration succeeds
+      loop_monitored_ = App.register_socket_fd(fd_);
+    } else {
+      loop_monitored_ = false;
+    }
+#else
+    // Without select support, ignore monitor_loop parameter
+    (void) monitor_loop;
+#endif
+  }
   ~LwIPSocketImpl() override {
     if (!closed_) {
       close();  // NOLINT(clang-analyzer-optin.cplusplus.VirtualCall)
@@ -41,16 +55,35 @@ class LwIPSocketImpl : public Socket {
   }
   int connect(const struct sockaddr *addr, socklen_t addrlen) override { return lwip_connect(fd_, addr, addrlen); }
   std::unique_ptr<Socket> accept(struct sockaddr *addr, socklen_t *addrlen) override {
+    return accept_impl_(addr, addrlen, false);
+  }
+  std::unique_ptr<Socket> accept_loop_monitored(struct sockaddr *addr, socklen_t *addrlen) override {
+    return accept_impl_(addr, addrlen, true);
+  }
+
+ private:
+  std::unique_ptr<Socket> accept_impl_(struct sockaddr *addr, socklen_t *addrlen, bool loop_monitored) {
     int fd = lwip_accept(fd_, addr, addrlen);
     if (fd == -1)
       return {};
-    return make_unique<LwIPSocketImpl>(fd);
+    return make_unique<LwIPSocketImpl>(fd, loop_monitored);
   }
+
+ public:
   int bind(const struct sockaddr *addr, socklen_t addrlen) override { return lwip_bind(fd_, addr, addrlen); }
   int close() override {
-    int ret = lwip_close(fd_);
-    closed_ = true;
-    return ret;
+    if (!closed_) {
+#ifdef USE_SOCKET_SELECT_SUPPORT
+      // Unregister from select() before closing if monitored
+      if (loop_monitored_) {
+        App.unregister_socket_fd(fd_);
+      }
+#endif
+      int ret = lwip_close(fd_);
+      closed_ = true;
+      return ret;
+    }
+    return 0;
   }
   int shutdown(int how) override { return lwip_shutdown(fd_, how); }
 
@@ -98,16 +131,27 @@ class LwIPSocketImpl : public Socket {
     return 0;
   }
 
+  int get_fd() const override { return fd_; }
+
  protected:
   int fd_;
   bool closed_ = false;
 };
 
-std::unique_ptr<Socket> socket(int domain, int type, int protocol) {
+// Helper to create a socket with optional monitoring
+static std::unique_ptr<Socket> create_socket(int domain, int type, int protocol, bool loop_monitored = false) {
   int ret = lwip_socket(domain, type, protocol);
   if (ret == -1)
     return nullptr;
-  return std::unique_ptr<Socket>{new LwIPSocketImpl(ret)};
+  return std::unique_ptr<Socket>{new LwIPSocketImpl(ret, loop_monitored)};
+}
+
+std::unique_ptr<Socket> socket(int domain, int type, int protocol) {
+  return create_socket(domain, type, protocol, false);
+}
+
+std::unique_ptr<Socket> socket_loop_monitored(int domain, int type, int protocol) {
+  return create_socket(domain, type, protocol, true);
 }
 
 }  // namespace socket

esphome/components/socket/socket.cpp

@@ -4,12 +4,35 @@
 #include <cstring>
 #include <string>
 #include "esphome/core/log.h"
+#include "esphome/core/application.h"
 
 namespace esphome {
 namespace socket {
 
 Socket::~Socket() {}
 
+bool Socket::ready() const {
+#ifdef USE_SOCKET_SELECT_SUPPORT
+  if (!loop_monitored_) {
+    // Non-monitored sockets always return true (assume data may be available)
+    return true;
+  }
+
+  // For loop-monitored sockets, check with the Application's select() results
+  int fd = this->get_fd();
+  if (fd < 0) {
+    // No valid file descriptor, assume ready (fallback behavior)
+    return true;
+  }
+
+  return App.is_socket_ready(fd);
+#else
+  // Without select() support, we can't monitor sockets in the loop
+  // Always return true (assume data may be available)
+  return true;
+#endif
+}
+
 std::unique_ptr<Socket> socket_ip(int type, int protocol) {
 #if USE_NETWORK_IPV6
   return socket(AF_INET6, type, protocol);
@@ -18,6 +41,14 @@ std::unique_ptr<Socket> socket_ip(int type, int protocol) {
 #endif /* USE_NETWORK_IPV6 */
 }
 
+std::unique_ptr<Socket> socket_ip_loop_monitored(int type, int protocol) {
+#if USE_NETWORK_IPV6
+  return socket_loop_monitored(AF_INET6, type, protocol);
+#else
+  return socket_loop_monitored(AF_INET, type, protocol);
+#endif /* USE_NETWORK_IPV6 */
+}
+
 socklen_t set_sockaddr(struct sockaddr *addr, socklen_t addrlen, const std::string &ip_address, uint16_t port) {
 #if USE_NETWORK_IPV6
   if (ip_address.find(':') != std::string::npos) {

esphome/components/socket/socket.h

@@ -17,6 +17,11 @@ class Socket {
   Socket &operator=(const Socket &) = delete;
 
   virtual std::unique_ptr<Socket> accept(struct sockaddr *addr, socklen_t *addrlen) = 0;
+  /// Accept a connection and monitor it in the main loop
+  /// NOTE: This function is NOT thread-safe and must only be called from the main loop
+  virtual std::unique_ptr<Socket> accept_loop_monitored(struct sockaddr *addr, socklen_t *addrlen) {
+    return accept(addr, addrlen);  // Default implementation for backward compatibility
+  }
   virtual int bind(const struct sockaddr *addr, socklen_t addrlen) = 0;
   virtual int close() = 0;
   // not supported yet:
@@ -44,14 +49,35 @@ 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; }
+
+  /// 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)
+  bool ready() const;
+
+ protected:
+#ifdef USE_SOCKET_SELECT_SUPPORT
+  bool loop_monitored_{false};  ///< Whether this socket is monitored by the event loop
+#endif
 };
 
 /// Create a socket of the given domain, type and protocol.
 std::unique_ptr<Socket> socket(int domain, int type, int protocol);
-
 /// Create a socket in the newest available IP domain (IPv6 or IPv4) of the given type and protocol.
 std::unique_ptr<Socket> socket_ip(int type, int protocol);
 
+/// Create a socket and monitor it for data in the main loop.
+/// Like socket() but also registers the socket with the Application's select() loop.
+/// WARNING: These functions are NOT thread-safe. They must only be called from the main loop
+/// as they register the socket file descriptor with the global Application instance.
+/// NOTE: On ESP platforms, FD_SETSIZE is typically 10, limiting the number of monitored sockets.
+/// File descriptors >= FD_SETSIZE will not be monitored and will log an error.
+std::unique_ptr<Socket> socket_loop_monitored(int domain, int type, int protocol);
+std::unique_ptr<Socket> socket_ip_loop_monitored(int type, int protocol);
+
 /// Set a sockaddr to the specified address and port for the IP version used by socket_ip().
 socklen_t set_sockaddr(struct sockaddr *addr, socklen_t addrlen, const std::string &ip_address, uint16_t port);