http_server: adds WebSocket support

This commit adds the WebSocket support for esp_http_server
library. It mainly does:

- Handling WebSocket handshake
  - Parsing HTTP upgrade request
  - Reply the upgrade request
- Receive WebSocket packets
  - Parse header, decode to a struct
  - Unmask payload (if required)
- Send WebSocket frames
- Receive WebSocket frame
- Automatic control frame handling

Merges https://github.com/espressif/esp-idf/pull/4306
Closes https://github.com/espressif/esp-idf/issues/4819

components/esp_http_server/CMakeLists.txt

@@ -3,8 +3,9 @@ idf_component_register(SRCS "src/httpd_main.c"
                             "src/httpd_sess.c"
                             "src/httpd_txrx.c"
                             "src/httpd_uri.c"
+                            "src/httpd_ws.c"
                             "src/util/ctrl_sock.c"
                     INCLUDE_DIRS "include"
                     PRIV_INCLUDE_DIRS "src/port/esp32" "src/util"
                     REQUIRES nghttp # for http_parser.h
-                    PRIV_REQUIRES lwip esp_timer) 
+                    PRIV_REQUIRES lwip mbedtls esp_timer)

components/esp_http_server/Kconfig

@@ -39,4 +39,10 @@ menu "HTTP Server"
             Enabling this will log discarded binary HTTP request data at Debug level.
             For large content data this may not be desirable as it will clutter the log.
 
+    config HTTPD_WS_SUPPORT
+        bool "WebSocket server support"
+        default y
+        help
+            This sets the WebSocket server support.
+
 endmenu

components/esp_http_server/include/esp_http_server.h

@@ -399,6 +399,14 @@ typedef struct httpd_uri {
      * Pointer to user context data which will be available to handler
      */
     void *user_ctx;
+
+#ifdef CONFIG_HTTPD_WS_SUPPORT
+    /**
+     * Flag for indicating a WebSocket endpoint.
+     * If this flag is true, then method must be HTTP_GET. Otherwise the handshake will not be handled.
+     */
+    bool is_websocket;
+#endif
 } httpd_uri_t;
 
 /**
@@ -1452,6 +1460,65 @@ esp_err_t httpd_queue_work(httpd_handle_t handle, httpd_work_fn_t work, void *ar
  * @}
  */
 
+/* ************** Group: WebSocket ************** */
+/** @name WebSocket
+ * Functions and structs for WebSocket server
+ * @{
+ */
+#ifdef CONFIG_HTTPD_WS_SUPPORT
+/**
+ * @brief Enum for WebSocket packet types (Opcode in the header)
+ * @note Please refer to RFC6455 Section 5.4 for more details
+ */
+typedef enum {
+    HTTPD_WS_TYPE_CONTINUE   = 0x0,
+    HTTPD_WS_TYPE_TEXT       = 0x1,
+    HTTPD_WS_TYPE_BINARY     = 0x2,
+    HTTPD_WS_TYPE_CLOSE      = 0x8,
+    HTTPD_WS_TYPE_PING       = 0x9,
+    HTTPD_WS_TYPE_PONG       = 0xA
+} httpd_ws_type_t;
+
+/**
+ * @brief WebSocket frame format
+ */
+typedef struct httpd_ws_frame {
+    bool final;                 /*!< Final frame */
+    httpd_ws_type_t type;       /*!< WebSocket frame type */
+    uint8_t *payload;           /*!< Pre-allocated data buffer */
+    size_t len;                 /*!< Length of the WebSocket data */
+} httpd_ws_frame_t;
+
+/**
+ * @brief Receive and parse a WebSocket frame
+ * @param[in]   req         Current request
+ * @param[out]  pkt         WebSocket packet
+ * @param[in]   max_len     Maximum length for receive
+ * @return
+ *  - ESP_OK                    : On successful
+ *  - ESP_FAIL                  : Socket errors occurs
+ *  - ESP_ERR_INVALID_STATE     : Handshake was already done beforehand
+ *  - ESP_ERR_INVALID_ARG       : Argument is invalid (null or non-WebSocket)
+ */
+esp_err_t httpd_ws_recv_frame(httpd_req_t *req, httpd_ws_frame_t *pkt, size_t max_len);
+
+/**
+ * @brief Construct and send a WebSocket frame
+ * @param[in]   req     Current request
+ * @param[in]   pkt     WebSocket frame
+ * @return
+ *  - ESP_OK                    : On successful
+ *  - ESP_FAIL                  : When socket errors occurs
+ *  - ESP_ERR_INVALID_STATE     : Handshake was already done beforehand
+ *  - ESP_ERR_INVALID_ARG       : Argument is invalid (null or non-WebSocket)
+ */
+esp_err_t httpd_ws_send_frame(httpd_req_t *req, httpd_ws_frame_t *pkt);
+
+#endif /* CONFIG_HTTPD_WS_SUPPORT */
+/** End of WebSocket related stuff
+ * @}
+ */
+
 #ifdef __cplusplus
 }
 #endif

components/esp_http_server/src/esp_httpd_priv.h

@@ -71,6 +71,11 @@ struct sock_db {
     uint64_t lru_counter;                   /*!< LRU Counter indicating when the socket was last used */
     char pending_data[PARSER_BLOCK_SIZE];   /*!< Buffer for pending data to be received */
     size_t pending_len;                     /*!< Length of pending data to be received */
+#ifdef CONFIG_HTTPD_WS_SUPPORT
+    bool ws_handshake_done;                 /*!< True if it has done WebSocket handshake (if this socket is a valid WS) */
+    bool ws_close;                          /*!< Set to true to close the socket later (when WS Close frame received) */
+    esp_err_t (*ws_handler)(httpd_req_t *r);   /*!< WebSocket handler, leave to null if it's not WebSocket */
+#endif
 };
 
 /**
@@ -91,6 +96,11 @@ struct httpd_req_aux {
         const char *value;
     } *resp_hdrs;                                   /*!< Additional headers in response packet */
     struct http_parser_url url_parse_res;           /*!< URL parsing result, used for retrieving URL elements */
+#ifdef CONFIG_HTTPD_WS_SUPPORT
+    bool ws_handshake_detect;                       /*!< WebSocket handshake detection flag */
+    httpd_ws_type_t ws_type;                        /*!< WebSocket frame type */
+    bool ws_final;                                  /*!< WebSocket FIN bit (final frame or not) */
+#endif
 };
 
 /**
@@ -471,6 +481,44 @@ int httpd_default_recv(httpd_handle_t hd, int sockfd, char *buf, size_t buf_len,
  * @}
  */
 
+/* ************** Group: WebSocket ************** */
+/** @name WebSocket
+ * Functions for WebSocket header parsing
+ * @{
+ */
+
+
+/**
+ * @brief   This function is for responding a WebSocket handshake
+ *
+ * @param[in] req    Pointer to handshake request that will be handled
+ * @return
+ *  - ESP_OK                        : When handshake is sucessful
+ *  - ESP_ERR_NOT_FOUND             : When some headers (Sec-WebSocket-*) are not found
+ *  - ESP_ERR_INVALID_VERSION       : The WebSocket version is not "13"
+ *  - ESP_ERR_INVALID_STATE         : Handshake was done beforehand
+ *  - ESP_ERR_INVALID_ARG           : Argument is invalid (null or non-WebSocket)
+ *  - ESP_FAIL                      : Socket failures
+ */
+esp_err_t httpd_ws_respond_server_handshake(httpd_req_t *req);
+
+/**
+ * @brief   This function is for getting a frame type
+ *          and responding a WebSocket control frame automatically
+ *
+ * @param[in] req    Pointer to handshake request that will be handled
+ * @return
+ *  - ESP_OK                        : When handshake is sucessful
+ *  - ESP_ERR_INVALID_ARG           : Argument is invalid (null or non-WebSocket)
+ *  - ESP_ERR_INVALID_STATE         : Received only some parts of a control frame
+ *  - ESP_FAIL                      : Socket failures
+ */
+esp_err_t httpd_ws_get_frame_type(httpd_req_t *req);
+
+/** End of WebSocket related functions
+ * @}
+ */
+
 #ifdef __cplusplus
 }
 #endif

components/esp_http_server/src/httpd_parse.c

@@ -374,15 +374,38 @@ static esp_err_t cb_headers_complete(http_parser *parser)
     ESP_LOGD(TAG, LOG_FMT("bytes read     = %d"),  parser->nread);
     ESP_LOGD(TAG, LOG_FMT("content length = %zu"), r->content_len);
 
+    /* Handle upgrade requests - only WebSocket is supported for now */
     if (parser->upgrade) {
-        ESP_LOGW(TAG, LOG_FMT("upgrade from HTTP not supported"));
+#ifdef CONFIG_HTTPD_WS_SUPPORT
-        /* There is no specific HTTP error code to notify the client that
+        ESP_LOGD(TAG, LOG_FMT("Got an upgrade request"));
-         * upgrade is not supported, thus sending 400 Bad Request */
+
+        /* If there's no "Upgrade" header field, then it's not WebSocket. */
+        char ws_upgrade_hdr_val[] = "websocket";
+        if (httpd_req_get_hdr_value_str(r, "Upgrade", ws_upgrade_hdr_val, sizeof(ws_upgrade_hdr_val)) != ESP_OK) {
+            ESP_LOGW(TAG, LOG_FMT("Upgrade header does not match the length of \"websocket\""));
             parser_data->error = HTTPD_400_BAD_REQUEST;
             parser_data->status = PARSING_FAILED;
             return ESP_FAIL;
         }
 
+        /* If "Upgrade" field's key is not "websocket", then we should also forget about it. */
+        if (strcasecmp("websocket", ws_upgrade_hdr_val) != 0) {
+            ESP_LOGW(TAG, LOG_FMT("Upgrade header found but it's %s"), ws_upgrade_hdr_val);
+            parser_data->error = HTTPD_400_BAD_REQUEST;
+            parser_data->status = PARSING_FAILED;
+            return ESP_FAIL;
+        }
+
+        /* Now set handshake flag to true */
+        ra->ws_handshake_detect = true;
+#else
+        ESP_LOGD(TAG, LOG_FMT("WS functions has been disabled, Upgrade request is not supported."));
+        parser_data->error = HTTPD_400_BAD_REQUEST;
+        parser_data->status = PARSING_FAILED;
+        return ESP_FAIL;
+#endif
+    }
+
     parser_data->status = PARSING_BODY;
     ra->remaining_len = r->content_len;
     return ESP_OK;
@@ -667,6 +690,7 @@ static void init_req_aux(struct httpd_req_aux *ra, httpd_config_t *config)
     ra->first_chunk_sent = 0;
     ra->req_hdrs_count = 0;
     ra->resp_hdrs_count = 0;
+    ra->ws_handshake_detect = false;
     memset(ra->resp_hdrs, 0, config->max_resp_headers * sizeof(struct resp_hdr));
 }
 
@@ -678,6 +702,13 @@ static void httpd_req_cleanup(httpd_req_t *r)
     if ((r->ignore_sess_ctx_changes == false) && (ra->sd->ctx != r->sess_ctx)) {
         httpd_sess_free_ctx(ra->sd->ctx, ra->sd->free_ctx);
     }
+
+    /* Close the socket when a WebSocket Close request is received */
+    if (ra->sd->ws_close) {
+        ESP_LOGD(TAG, LOG_FMT("Try closing WS connection at FD: %d"), ra->sd->fd);
+        httpd_sess_trigger_close(r->handle, ra->sd->fd);
+    }
+
     /* Retrieve session info from the request into the socket database. */
     ra->sd->ctx = r->sess_ctx;
     ra->sd->free_ctx = r->free_ctx;
@@ -699,23 +730,62 @@ esp_err_t httpd_req_new(struct httpd_data *hd, struct sock_db *sd)
     init_req_aux(&hd->hd_req_aux, &hd->config);
     r->handle = hd;
     r->aux = &hd->hd_req_aux;
+
     /* Associate the request to the socket */
     struct httpd_req_aux *ra = r->aux;
     ra->sd = sd;
+
     /* Set defaults */
     ra->status = (char *)HTTPD_200;
     ra->content_type = (char *)HTTPD_TYPE_TEXT;
     ra->first_chunk_sent = false;
+
     /* Copy session info to the request */
     r->sess_ctx = sd->ctx;
     r->free_ctx = sd->free_ctx;
     r->ignore_sess_ctx_changes = sd->ignore_sess_ctx_changes;
-    /* Parse request */
+
-    esp_err_t err = httpd_parse_req(hd);
+    esp_err_t ret;
-    if (err != ESP_OK) {
+
+#ifdef CONFIG_HTTPD_WS_SUPPORT
+    /* Handle WebSocket */
+    ESP_LOGD(TAG, LOG_FMT("New request, has WS? %s, sd->ws_handler valid? %s, sd->ws_close? %s"),
+             sd->ws_handshake_done ? "Yes" : "No",
+             sd->ws_handler != NULL ? "Yes" : "No",
+             sd->ws_close ? "Yes" : "No");
+    if (sd->ws_handshake_done && sd->ws_handler != NULL) {
+        ESP_LOGD(TAG, LOG_FMT("New WS request from existing socket"));
+        ret = httpd_ws_get_frame_type(r);
+
+        /*  Stop and return here immediately if it's a CLOSE frame */
+        if (ra->ws_type == HTTPD_WS_TYPE_CLOSE) {
+            sd->ws_close = true;
+            return ret;
+        }
+
+        /* Ignore PONG frame, as this is a server */
+        if (ra->ws_type == HTTPD_WS_TYPE_PONG) {
+            return ret;
+        }
+
+        /* Call handler if it's a non-control frame */
+        if (ret == ESP_OK && ra->ws_type < HTTPD_WS_TYPE_CLOSE) {
+            ret = sd->ws_handler(r);
+        }
+
+        if (ret != ESP_OK) {
             httpd_req_cleanup(r);
         }
-    return err;
+        return ret;
+    }
+#endif
+
+    /* Parse request */
+    ret = httpd_parse_req(hd);
+    if (ret != ESP_OK) {
+        httpd_req_cleanup(r);
+    }
+    return ret;
 }
 
 /* Function that resets the http request data

components/esp_http_server/src/httpd_sess.c

@@ -281,7 +281,9 @@ bool httpd_sess_pending(struct httpd_data *hd, int fd)
     if (sd->pending_fn) {
         // test if there's any data to be read (besides read() function, which is handled by select() in the main httpd loop)
         // this should check e.g. for the SSL data buffer
-        if (sd->pending_fn(hd, fd) > 0) return true;
+        if (sd->pending_fn(hd, fd) > 0) {
+            return true;
+        }
     }
 
     return (sd->pending_len != 0);

components/esp_http_server/src/httpd_uri.c

@@ -172,6 +172,9 @@ esp_err_t httpd_register_uri_handler(httpd_handle_t handle,
             hd->hd_calls[i]->method   = uri_handler->method;
             hd->hd_calls[i]->handler  = uri_handler->handler;
             hd->hd_calls[i]->user_ctx = uri_handler->user_ctx;
+#ifdef CONFIG_HTTPD_WS_SUPPORT
+            hd->hd_calls[i]->is_websocket = uri_handler->is_websocket;
+#endif
             ESP_LOGD(TAG, LOG_FMT("[%d] installed %s"), i, uri_handler->uri);
             return ESP_OK;
         }
@@ -276,6 +279,7 @@ esp_err_t httpd_uri(struct httpd_data *hd)
 {
     httpd_uri_t            *uri = NULL;
     httpd_req_t            *req = &hd->hd_req;
+    struct httpd_req_aux   *aux = req->aux;
     struct http_parser_url *res = &hd->hd_req_aux.url_parse_res;
 
     /* For conveying URI not found/method not allowed */
@@ -307,6 +311,23 @@ esp_err_t httpd_uri(struct httpd_data *hd)
     /* Attach user context data (passed during URI registration) into request */
     req->user_ctx = uri->user_ctx;
 
+    /* Final step for a WebSocket handshake verification */
+#ifdef CONFIG_HTTPD_WS_SUPPORT
+    if (uri->is_websocket && aux->ws_handshake_detect && uri->method == HTTP_GET) {
+        ESP_LOGD(TAG, LOG_FMT("Responding WS handshake to sock %d"), aux->sd->fd);
+        esp_err_t ret = httpd_ws_respond_server_handshake(&hd->hd_req);
+        if (ret != ESP_OK) {
+            return ret;
+        }
+
+        aux->sd->ws_handshake_done = true;
+        aux->sd->ws_handler = uri->handler;
+
+        /* Return immediately after handshake, no need to call handler here */
+        return ESP_OK;
+    }
+#endif
+
     /* Invoke handler */
     if (uri->handler(req) != ESP_OK) {
         /* Handler returns error, this socket should be closed */

components/esp_http_server/src/httpd_ws.c

@@ -0,0 +1,374 @@
+// Copyright 2020 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+
+
+#include <stdlib.h>
+#include <sys/random.h>
+#include <esp_log.h>
+#include <esp_err.h>
+#include <mbedtls/sha1.h>
+#include <mbedtls/base64.h>
+
+#include <esp_http_server.h>
+#include "esp_httpd_priv.h"
+
+#ifdef CONFIG_HTTPD_WS_SUPPORT
+
+#define TAG "httpd_ws"
+
+/*
+ * Bit masks for WebSocket frames.
+ * Please refer to RFC6455 Section 5.2 for more details.
+ */
+#define HTTPD_WS_FIN_BIT        0x80U
+#define HTTPD_WS_OPCODE_BITS    0x0fU
+#define HTTPD_WS_MASK_BIT       0x80U
+#define HTTPD_WS_LENGTH_BITS    0x7fU
+
+/*
+ * The magic GUID string used for handshake
+ * Please refer to RFC6455 Section 1.3 for more details.
+ */
+static const char ws_magic_uuid[] = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
+
+esp_err_t httpd_ws_respond_server_handshake(httpd_req_t *req)
+{
+    /* Probe if input parameters are valid or not */
+    if (!req || !req->aux) {
+        ESP_LOGW(TAG, LOG_FMT("Argument is invalid"));
+        return ESP_ERR_INVALID_ARG;
+    }
+
+    /* Detect handshake - reject if handshake was ALREADY performed */
+    struct httpd_req_aux *req_aux = req->aux;
+    if (req_aux->sd->ws_handshake_done) {
+        ESP_LOGW(TAG, LOG_FMT("State is invalid - Handshake has been performed"));
+        return ESP_ERR_INVALID_STATE;
+    }
+
+    /* Detect WS version existence */
+    char version_val[3] = { '\0' };
+    if (httpd_req_get_hdr_value_str(req, "Sec-WebSocket-Version", version_val, sizeof(version_val)) != ESP_OK) {
+        ESP_LOGW(TAG, LOG_FMT("\"Sec-WebSocket-Version\" is not found"));
+        return ESP_ERR_NOT_FOUND;
+    }
+
+    /* Detect if WS version is "13" or not.
+     * WS version must be 13 for now. Please refer to RFC6455 Section 4.1, Page 18 for more details. */
+    if (strcasecmp(version_val, "13") != 0) {
+        ESP_LOGW(TAG, LOG_FMT("\"Sec-WebSocket-Version\" is not \"13\", it is: %s"), version_val);
+        return ESP_ERR_INVALID_VERSION;
+    }
+
+    /* Grab Sec-WebSocket-Key (client key) from the header */
+    /* Size of base64 coded string is equal '((input_size * 4) / 3) + (input_size / 96) + 6' including Z-term */
+    char sec_key_encoded[28] = { '\0' };
+    if (httpd_req_get_hdr_value_str(req, "Sec-WebSocket-Key", sec_key_encoded, sizeof(sec_key_encoded)) != ESP_OK) {
+        ESP_LOGW(TAG, LOG_FMT("Cannot find client key"));
+        return ESP_ERR_NOT_FOUND;
+    }
+
+    /* Prepare server key (Sec-WebSocket-Accept), concat the string */
+    char server_key_encoded[33] = { '\0' };
+    uint8_t server_key_hash[20] = { 0 };
+    char server_raw_text[sizeof(sec_key_encoded) + sizeof(ws_magic_uuid) + 1] = { '\0' };
+
+    strcpy(server_raw_text, sec_key_encoded);
+    strcat(server_raw_text, ws_magic_uuid);
+
+    ESP_LOGD(TAG, LOG_FMT("Server key before encoding: %s"), server_raw_text);
+
+    /* Generate SHA-1 first and then encode to Base64 */
+    size_t key_len = strlen(server_raw_text);
+    mbedtls_sha1_ret((uint8_t *)server_raw_text, key_len, server_key_hash);
+
+    size_t encoded_len = 0;
+    mbedtls_base64_encode((uint8_t *)server_key_encoded, sizeof(server_key_encoded), &encoded_len,
+                          server_key_hash, sizeof(server_key_hash));
+
+    ESP_LOGD(TAG, LOG_FMT("Generated server key: %s"), server_key_encoded);
+
+    /* Prepare the Switching Protocol response */
+    char tx_buf[192] = { '\0' };
+    int fmt_len = snprintf(tx_buf, sizeof(tx_buf),
+                           "HTTP/1.1 101 Switching Protocols\r\n"
+                           "Upgrade: websocket\r\n"
+                           "Connection: Upgrade\r\n"
+                           "Sec-WebSocket-Accept: %s\r\n\r\n", server_key_encoded);
+    if (fmt_len < 0 || fmt_len > sizeof(tx_buf)) {
+        ESP_LOGW(TAG, LOG_FMT("Failed to prepare Tx buffer"));
+        return ESP_FAIL;
+    }
+
+    /* Send off the response */
+    if (httpd_send(req, tx_buf, fmt_len) < 0) {
+        ESP_LOGW(TAG, LOG_FMT("Failed to send the response"));
+        return ESP_FAIL;
+    }
+
+    return ESP_OK;
+}
+
+static esp_err_t httpd_ws_check_req(httpd_req_t *req)
+{
+    /* Probe if input parameters are valid or not */
+    if (!req || !req->aux) {
+        ESP_LOGW(TAG, LOG_FMT("Argument is null"));
+        return ESP_ERR_INVALID_ARG;
+    }
+
+    /* Detect handshake - reject if handshake was NOT YET performed */
+    struct httpd_req_aux *req_aux = req->aux;
+    if (!req_aux->sd->ws_handshake_done) {
+        ESP_LOGW(TAG, LOG_FMT("State is invalid - No handshake performed"));
+        return ESP_ERR_INVALID_STATE;
+    }
+
+    return ESP_OK;
+}
+
+static esp_err_t httpd_ws_unmask_payload(uint8_t *payload, size_t len, const uint8_t *mask_key)
+{
+    if (len < 1 || !payload) {
+        ESP_LOGW(TAG, LOG_FMT("Invalid payload provided"));
+        return ESP_ERR_INVALID_ARG;
+    }
+
+    for (size_t idx = 0; idx < len; idx++) {
+        payload[idx] = (payload[idx] ^ mask_key[idx % 4]);
+    }
+
+    return ESP_OK;
+}
+
+esp_err_t httpd_ws_recv_frame(httpd_req_t *req, httpd_ws_frame_t *frame, size_t max_len)
+{
+    esp_err_t ret = httpd_ws_check_req(req);
+    if (ret != ESP_OK) {
+        return ret;
+    }
+
+    struct httpd_req_aux *aux = req->aux;
+    if (aux == NULL) {
+        ESP_LOGW(TAG, LOG_FMT("Invalid Aux pointer"));
+        return ESP_ERR_INVALID_ARG;
+    }
+
+    if (!frame) {
+        ESP_LOGW(TAG, LOG_FMT("Frame pointer is invalid"));
+        return ESP_ERR_INVALID_ARG;
+    }
+
+    /* Assign the frame info from the previous reading */
+    frame->type = aux->ws_type;
+    frame->final = aux->ws_final;
+
+    /* Grab the second byte */
+    uint8_t second_byte = 0;
+    if (httpd_recv_with_opt(req, (char *)&second_byte, sizeof(second_byte), false) <= 0) {
+        ESP_LOGW(TAG, LOG_FMT("Failed to receive the second byte"));
+        return ESP_FAIL;
+    }
+
+    /* Parse the second byte */
+    /* Please refer to RFC6455 Section 5.2 for more details */
+    bool masked = (second_byte & HTTPD_WS_MASK_BIT) != 0;
+
+    /* Interpret length */
+    uint8_t init_len = second_byte & HTTPD_WS_LENGTH_BITS;
+    if (init_len < 126) {
+        /* Case 1: If length is 0-125, then this length bit is 7 bits */
+        frame->len = init_len;
+    } else if (init_len == 126) {
+        /* Case 2: If length byte is 126, then this frame's length bit is 16 bits */
+        uint8_t length_bytes[2] = { 0 };
+        if (httpd_recv_with_opt(req, (char *)length_bytes, sizeof(length_bytes), false) <= 0) {
+            ESP_LOGW(TAG, LOG_FMT("Failed to receive 2 bytes length"));
+            return ESP_FAIL;
+        }
+
+        frame->len = ((uint32_t)(length_bytes[0] << 8U) | (length_bytes[1]));
+    } else if (init_len == 127) {
+        /* Case 3: If length is byte 127, then this frame's length bit is 64 bits */
+        uint8_t length_bytes[8] = { 0 };
+        if (httpd_recv_with_opt(req, (char *)length_bytes, sizeof(length_bytes), false) <= 0) {
+            ESP_LOGW(TAG, LOG_FMT("Failed to receive 2 bytes length"));
+            return ESP_FAIL;
+        }
+
+        frame->len = (((uint64_t)length_bytes[0] << 56U) |
+                    ((uint64_t)length_bytes[1] << 48U) |
+                    ((uint64_t)length_bytes[2] << 40U) |
+                    ((uint64_t)length_bytes[3] << 32U) |
+                    ((uint64_t)length_bytes[4] << 24U) |
+                    ((uint64_t)length_bytes[5] << 16U) |
+                    ((uint64_t)length_bytes[6] <<  8U) |
+                    ((uint64_t)length_bytes[7]));
+    }
+
+    /* We only accept the incoming packet length that is smaller than the max_len (or it will overflow the buffer!) */
+    if (frame->len > max_len) {
+        ESP_LOGW(TAG, LOG_FMT("WS Message too long"));
+        return ESP_ERR_INVALID_SIZE;
+    }
+
+    /* If this frame is masked, dump the mask as well */
+    uint8_t mask_key[4] = { 0 };
+    if (masked) {
+        if (httpd_recv_with_opt(req, (char *)mask_key, sizeof(mask_key), false) <= 0) {
+            ESP_LOGW(TAG, LOG_FMT("Failed to receive mask key"));
+            return ESP_FAIL;
+        }
+    } else {
+        /* If the WS frame from client to server is not masked, it should be rejected.
+         * Please refer to RFC6455 Section 5.2 for more details. */
+        ESP_LOGW(TAG, LOG_FMT("WS frame is not properly masked."));
+        return ESP_ERR_INVALID_STATE;
+    }
+
+    /* Receive buffer */
+    /* If there's nothing to receive, return and stop here. */
+    if (frame->len == 0) {
+        return ESP_OK;
+    }
+
+    if (frame->payload == NULL) {
+        ESP_LOGW(TAG, LOG_FMT("Payload buffer is null"));
+        return ESP_FAIL;
+    }
+
+    if (httpd_recv_with_opt(req, (char *)frame->payload, frame->len, false) <= 0) {
+        ESP_LOGW(TAG, LOG_FMT("Failed to receive payload"));
+        return ESP_FAIL;
+    }
+
+    /* Unmask payload */
+    httpd_ws_unmask_payload(frame->payload, frame->len, mask_key);
+
+    return ESP_OK;
+}
+
+esp_err_t httpd_ws_send_frame(httpd_req_t *req, httpd_ws_frame_t *frame)
+{
+    esp_err_t ret = httpd_ws_check_req(req);
+    if (ret != ESP_OK) {
+        return ret;
+    }
+    if (!frame) {
+        ESP_LOGW(TAG, LOG_FMT("Argument is invalid"));
+        return ESP_ERR_INVALID_ARG;
+    }
+
+    /* Prepare Tx buffer - maximum length is 14, which includes 2 bytes header, 8 bytes length, 4 bytes mask key */
+    uint8_t tx_len = 0;
+    uint8_t header_buf[10] = {0 };
+    header_buf[0] |= frame->final ? HTTPD_WS_FIN_BIT : 0; /* Final (FIN) bit */
+    header_buf[0] |= frame->type; /* Type (opcode): 4 bits */
+
+    if (frame->len <= 125) {
+        header_buf[1] = frame->len & 0x7fU; /* Length for 7 bits */
+        tx_len = 2;
+    } else if (frame->len > 125 && frame->len < UINT16_MAX) {
+        header_buf[1] = 126;                /* Length for 16 bits */
+        header_buf[2] = (frame->len >> 8U) & 0xffU;
+        header_buf[3] = frame->len & 0xffU;
+        tx_len = 4;
+    } else {
+        header_buf[1] = 127;                /* Length for 64 bits */
+        uint8_t shift_idx = sizeof(uint64_t) - 1; /* Shift index starts at 7 */
+        for (int8_t idx = 2; idx > 9; idx--) {
+            /* Now do shifting (be careful of endianess, i.e. when buffer index is 2, frame length shift index is 7) */
+            header_buf[idx] = (frame->len >> (uint8_t)(shift_idx * 8)) & 0xffU;
+            shift_idx--;
+        }
+        tx_len = 10;
+    }
+
+    /* WebSocket server does not required to mask response payload, so leave the MASK bit as 0. */
+    header_buf[1] &= (~HTTPD_WS_MASK_BIT);
+
+    /* Send off header */
+    if (httpd_send(req, (const char *)header_buf, tx_len) < 0) {
+        ESP_LOGW(TAG, LOG_FMT("Failed to send WS header"));
+        return ESP_FAIL;
+    }
+
+    /* Send off payload */
+    if(frame->len > 0 && frame->payload != NULL) {
+        if (httpd_send(req, (const char *)frame->payload, frame->len) < 0) {
+            ESP_LOGW(TAG, LOG_FMT("Failed to send WS payload"));
+            return ESP_FAIL;
+        }
+    }
+
+    return ESP_OK;
+}
+
+esp_err_t httpd_ws_get_frame_type(httpd_req_t *req)
+{
+    esp_err_t ret = httpd_ws_check_req(req);
+    if (ret != ESP_OK) {
+        return ret;
+    }
+
+    struct httpd_req_aux *aux = req->aux;
+    if (aux == NULL) {
+        ESP_LOGW(TAG, LOG_FMT("Invalid Aux pointer"));
+        return ESP_ERR_INVALID_ARG;
+    }
+
+    /* Read the first byte from the frame to get the FIN flag and Opcode */
+    /* Please refer to RFC6455 Section 5.2 for more details */
+    uint8_t first_byte = 0;
+    if (httpd_recv_with_opt(req, (char *)&first_byte, sizeof(first_byte), false) <= 0) {
+        /* If the recv() return code is <= 0, then this socket FD is invalid (i.e. a broken connection) */
+        /* Here we mark it as a Close message and close it later. */
+        ESP_LOGW(TAG, LOG_FMT("Failed to read header byte (socket FD invalid), closing socket now"));
+        aux->ws_final = true;
+        aux->ws_type = HTTPD_WS_TYPE_CLOSE;
+        return ESP_OK;
+    }
+
+    ESP_LOGD(TAG, LOG_FMT("First byte received: 0x%02X"), first_byte);
+
+    /* Decode the FIN flag and Opcode from the byte */
+    aux->ws_final = (first_byte & HTTPD_WS_FIN_BIT) != 0;
+    aux->ws_type = (first_byte & HTTPD_WS_OPCODE_BITS);
+
+    /* Reply to PING. For PONG and CLOSE, it will be handled elsewhere. */
+    if(aux->ws_type == HTTPD_WS_TYPE_PING) {
+        ESP_LOGD(TAG, LOG_FMT("Got a WS PING frame, Replying PONG..."));
+
+        /* Read the rest of the PING frame, for PONG to reply back. */
+        /* Please refer to RFC6455 Section 5.5.2 for more details */
+        httpd_ws_frame_t frame;
+        uint8_t frame_buf[128] = { 0 };
+        memset(&frame, 0, sizeof(httpd_ws_frame_t));
+        frame.payload = frame_buf;
+
+        if(httpd_ws_recv_frame(req, &frame, 126) != ESP_OK) {
+            ESP_LOGD(TAG, LOG_FMT("Cannot receive the full PING frame"));
+            return ESP_ERR_INVALID_STATE;
+        }
+
+        /* Now turn the frame to PONG */
+        frame.type = HTTPD_WS_TYPE_PONG;
+        return httpd_ws_send_frame(req, &frame);
+    }
+
+    return ESP_OK;
+}
+
+#endif /* CONFIG_HTTPD_WS_SUPPORT */