# HTTP Server

[中文]

## Overview

The HTTP Server component provides an ability for running a lightweight web server on ESP32-S2. Following are detailed steps to use the API exposed by HTTP Server:

> - `httpd_start()`: Creates an instance of HTTP server, allocate memory/resources for it depending upon the specified configuration and outputs a handle to the server instance. The server has both, a listening socket (TCP) for HTTP traffic, and a control socket (UDP) for control signals, which are selected in a round robin fashion in the server task loop. The task priority and stack size are configurable during server instance creation by passing `httpd_config_t` structure to `httpd_start()`. TCP traffic is parsed as HTTP requests and, depending on the requested URI, user registered handlers are invoked which are supposed to send back HTTP response packets.

> - `httpd_stop()`: This stops the server with the provided handle and frees up any associated memory/resources. This is a blocking function that first signals a halt to the server task and then waits for the task to terminate. While stopping, the task closes all open connections, removes registered URI handlers and resets all session context data to empty.

> - `httpd_register_uri_handler()`: A URI handler is registered by passing object of type `httpd_uri_t` structure which has members including `uri` name, `method` type (eg. `HTTP_GET/HTTP_POST/HTTP_PUT` etc.), function pointer of type `esp_err_t *handler (httpd_req_t *req)` and `user_ctx` pointer to user context data.

## Application Examples

- protocols/http_server/simple demonstrates how to handle arbitrary content lengths, read request headers and URL query parameters, and set response headers.

- protocols/http_server/advanced_tests demonstrates how to use the HTTP server for advanced testing.

## Persistent Connections

HTTP server features persistent connections, allowing for the reuse of the same connection (session) for several transfers, all the while maintaining context specific data for the session. Context data may be allocated dynamically by the handler in which case a custom function may need to be specified for freeing this data when the connection/session is closed.

### Persistent Connections Example

    /* Custom function to free context */
    void free_ctx_func(void *ctx)
    {
        /* Could be something other than free */
        free(ctx);
    }

    esp_err_t adder_post_handler(httpd_req_t *req)
    {
        /* Create session's context if not already available */
        if (! req->sess_ctx) {
            req->sess_ctx = malloc(sizeof(ANY_DATA_TYPE));  /*!< Pointer to context data */
            req->free_ctx = free_ctx_func;                  /*!< Function to free context data */
        }

        /* Access context data */
        ANY_DATA_TYPE *ctx_data = (ANY_DATA_TYPE *)req->sess_ctx;

        /* Respond */
        ...............
        ...............
        ...............

        return ESP_OK;
    }

Check the example under protocols/http_server/persistent_sockets. This example demonstrates how to set up and use an HTTP server with persistent sockets, allowing for independent sessions or contexts per client.

## WebSocket Server

The HTTP server component provides WebSocket support. The WebSocket feature can be enabled in menuconfig using the CONFIG_HTTPD_WS_SUPPORT option.

protocols/http_server/ws_echo_server demonstrates how to create a WebSocket echo server using the HTTP server, which starts on a local network and requires a WebSocket client for interaction, echoing back received WebSocket frames.

### WebSocket Pre-Handshake Callback

The HTTP server component provides a pre-handshake callback for WebSocket endpoints. This callback is invoked before the WebSocket handshake is processed — at this point, the connection is still an HTTP connection and has not yet been upgraded to WebSocket.

The pre-handshake callback can be used for authentication, authorization, or other checks. If the callback returns `ESP_OK`, the WebSocket handshake will proceed. If the callback returns any other value, the handshake will be aborted and the connection will be closed.

To use the WebSocket pre-handshake callback, you must enable CONFIG_HTTPD_WS_PRE_HANDSHAKE_CB_SUPPORT in your project configuration.

    static esp_err_t ws_auth_handler(httpd_req_t *req)
    {
        // Your authentication logic here
        // return ESP_OK to allow the handshake, or another value to reject.
        return ESP_OK;
    }

    // Registering a WebSocket URI handler with pre-handshake authentication
    static const httpd_uri_t ws = {
        .uri        = "/ws",
        .method     = HTTP_GET,
        .handler    = handler,           // Your WebSocket data handler
        .user_ctx   = NULL,
        .is_websocket = true,
        .ws_pre_handshake_cb = ws_auth_handler // Set the pre-handshake callback
    };

    // Register the handler after starting the server:
    httpd_register_uri_handler(server, &ws);

## Event Handling

ESP HTTP server has various events for which a handler can be triggered by the Event Loop library when the particular event occurs. The handler has to be registered using `esp_event_handler_register()`. This helps in event handling for ESP HTTP server.

`esp_http_server_event_id_t` has all the events which can happen for ESP HTTP server.

Expected data type for different ESP HTTP server events in event loop:

> - HTTP_SERVER_EVENT_ERROR : `httpd_err_code_t`

> - HTTP_SERVER_EVENT_START : `NULL`

> - HTTP_SERVER_EVENT_ON_CONNECTED : `int`

> - HTTP_SERVER_EVENT_ON_HEADER : `int`

> - HTTP_SERVER_EVENT_HEADERS_SENT : `int`

> - HTTP_SERVER_EVENT_ON_DATA : `esp_http_server_event_data`

> - HTTP_SERVER_EVENT_SENT_DATA : `esp_http_server_event_data`

> - HTTP_SERVER_EVENT_DISCONNECTED : `int`

> - HTTP_SERVER_EVENT_STOP : `NULL`

## File Serving

protocols/http_server/file_serving demonstrates how to create a simple HTTP file server, with both upload and download capabilities.

## Captive Portal

protocols/http_server/captive_portal demonstrates two methods of creating a captive portal, which directs users to an authentication page before browsing, using either DNS queries and HTTP requests redirection or a modern method involving a field in the DHCP offer.

## Asynchronous Handlers

protocols/http_server/async_handlers demonstrates how to handle multiple long-running simultaneous requests within the HTTP server, using different URIs for asynchronous requests, quick requests, and the index page.

## RESTful API

protocols/http_server/restful_server demonstrates how to implement a RESTful API server and HTTP server, with a frontend browser UI, and designs several APIs to fetch resources, using mDNS to parse the domain name, and deploying the webpage to host PC via semihost technology or to SPI flash or SD Card.

## URI Handlers

The HTTP server allows you to register URI handlers to handle different HTTP requests. Each URI handler is associated with a specific URI and HTTP method (GET, POST, etc.). The handler function is called whenever a request matching the URI and method is received.

The handler function should return an `esp_err_t` value.

    esp_err_t my_uri_handler(httpd_req_t *req)
    {
        // Handle the request
        // ...

        // Return ESP_OK if the request was handled successfully
        return ESP_OK;

        // Return an error code to close the connection
        // return ESP_FAIL;
    }

    void register_uri_handlers(httpd_handle_t server)
    {
        httpd_uri_t my_uri = {
            .uri       = "/my_uri",
            .method    = HTTP_GET,
            .handler   = my_uri_handler,
            .user_ctx  = NULL
        };

        httpd_register_uri_handler(server, &my_uri);
    }

In this example, the my_uri_handler function handles requests to the /my_uri URI. If the handler returns `ESP_OK`, the connection remains open. If it returns any other value, the connection is closed. This behavior allows the application to manage connection closure based on specific events or conditions.

## API Reference

### Header File

- components/esp_http_server/include/esp_http_server.h

- This header file can be included with:

  >     #include "esp_http_server.h"

- This header file is a part of the API provided by the `esp_http_server` component. To declare that your component depends on `esp_http_server`, add the following to your CMakeLists.txt:

  >     REQUIRES esp_http_server

  > or

  >     PRIV_REQUIRES esp_http_server

### Functions

esp_err_t httpd_start(httpd_handle_t *handle, const httpd_config_t *config)

  Starts the web server.

  Create an instance of HTTP server and allocate memory/resources for it depending upon the specified configuration.

  Example usage:

      //Function for starting the webserver
      httpd_handle_t start_webserver(void)
      {
      // Generate default configuration
      httpd_config_t config = HTTPD_DEFAULT_CONFIG();

      // Empty handle to http_server
           httpd_handle_t server = NULL;

      // Start the httpd server
      if (httpd_start(&server, &config) == ESP_OK) {
      // Register URI handlers
               httpd_register_uri_handler(server, &uri_get);
               httpd_register_uri_handler(server, &uri_post);
           }
      // If server failed to start, handle will be NULL
      return server;
      }

  Parameters:

    - config -- [in] Configuration for new instance of the server

    - handle -- [out] Handle to newly created instance of the server. NULL on error

  Returns:

    - ESP_OK : Instance created successfully

    - ESP_ERR_INVALID_ARG : Null argument(s)

    - ESP_ERR_HTTPD_ALLOC_MEM : Failed to allocate memory for instance

    - ESP_ERR_HTTPD_TASK : Failed to launch server task

esp_err_t httpd_stop(httpd_handle_t handle)

  Stops the web server.

  Deallocates memory/resources used by an HTTP server instance and deletes it. Once deleted the handle can no longer be used for accessing the instance.

  Example usage:

      // Function for stopping the webserver
      void stop_webserver(httpd_handle_t server)
      {
      // Ensure handle is non NULL
      if (server != NULL) {
      // Stop the httpd server
               httpd_stop(server);
           }
      }

  Parameters:

    handle -- [in] Handle to server returned by httpd_start

  Returns:

    - ESP_OK : Server stopped successfully

    - ESP_ERR_INVALID_ARG : Handle argument is Null

esp_err_t httpd_sess_set_recv_override(httpd_handle_t hd, int sockfd, httpd_recv_func_t recv_func)

  Override web server's receive function (by session FD)

  This function overrides the web server's receive function. This same function is used to read HTTP request packets.

  Note

  This API is supposed to be called either from the context of

  - an http session APIs where sockfd is a valid parameter

  - a URI handler where sockfd is obtained using httpd_req_to_sockfd()

  Parameters:

    - hd -- [in] HTTPD instance handle

    - sockfd -- [in] Session socket FD

    - recv_func -- [in] The receive function to be set for this session

  Returns:

    - ESP_OK : On successfully registering override

    - ESP_ERR_INVALID_ARG : Null arguments

esp_err_t httpd_sess_set_send_override(httpd_handle_t hd, int sockfd, httpd_send_func_t send_func)

  Override web server's send function (by session FD)

  This function overrides the web server's send function. This same function is used to send out any response to any HTTP request.

  Note

  This API is supposed to be called either from the context of

  - an http session APIs where sockfd is a valid parameter

  - a URI handler where sockfd is obtained using httpd_req_to_sockfd()

  Parameters:

    - hd -- [in] HTTPD instance handle

    - sockfd -- [in] Session socket FD

    - send_func -- [in] The send function to be set for this session

  Returns:

    - ESP_OK : On successfully registering override

    - ESP_ERR_INVALID_ARG : Null arguments

esp_err_t httpd_sess_set_pending_override(httpd_handle_t hd, int sockfd, httpd_pending_func_t pending_func)

  Override web server's pending function (by session FD)

  This function overrides the web server's pending function. This function is used to test for pending bytes in a socket.

  Note

  This API is supposed to be called either from the context of

  - an http session APIs where sockfd is a valid parameter

  - a URI handler where sockfd is obtained using httpd_req_to_sockfd()

  Parameters:

    - hd -- [in] HTTPD instance handle

    - sockfd -- [in] Session socket FD

    - pending_func -- [in] The receive function to be set for this session

  Returns:

    - ESP_OK : On successfully registering override

    - ESP_ERR_INVALID_ARG : Null arguments

esp_err_t httpd_req_async_handler_begin(httpd_req_t *r, httpd_req_t **out)

  Start an asynchronous request. This function can be called in a request handler to get a request copy that can be used on a async thread.

  Note

  - This function is necessary in order to handle multiple requests simultaneously. See examples/async_requests for example usage.

  - You must call httpd_req_async_handler_complete() when you are done with the request.

  Parameters:

    - r -- [in] The request to create an async copy of

    - out -- [out] A newly allocated request which can be used on an async thread

  Returns:

    - ESP_OK : async request object created

esp_err_t httpd_req_async_handler_complete(httpd_req_t *r)

  Mark an asynchronous request as completed. This will.

  - free the request memory

  - relinquish ownership of the underlying socket, so it can be reused.

  - allow the http server to close our socket if needed (lru_purge_enable)

  Note

  If async requests are not marked completed, eventually the server will no longer accept incoming connections. The server will log a "httpd_accept_conn: error in accept (23)" message if this happens.

  Parameters:

    r -- [in] The request to mark async work as completed

  Returns:

    - ESP_OK : async request was marked completed

int httpd_req_to_sockfd(httpd_req_t *r)

  Get the Socket Descriptor from the HTTP request.

  This API will return the socket descriptor of the session for which URI handler was executed on reception of HTTP request. This is useful when user wants to call functions that require session socket fd, from within a URI handler, ie. : httpd_sess_get_ctx(), httpd_sess_trigger_close(), httpd_sess_update_lru_counter().

  Note

  This API is supposed to be called only from the context of a URI handler where httpd_req_t* request pointer is valid.

  Parameters:

    r -- [in] The request whose socket descriptor should be found

  Returns:

    - Socket descriptor : The socket descriptor for this request

    - -1 : Invalid/NULL request pointer

int httpd_req_recv(httpd_req_t *r, char *buf, size_t buf_len)

  API to read content data from the HTTP request.

  This API will read HTTP content data from the HTTP request into provided buffer. Use content_len provided in httpd_req_t structure to know the length of data to be fetched. If content_len is too large for the buffer then user may have to make multiple calls to this function, each time fetching 'buf_len' number of bytes, while the pointer to content data is incremented internally by the same number.

  Note

  - This API is supposed to be called only from the context of a URI handler where httpd_req_t* request pointer is valid.

  - If an error is returned, the URI handler must further return an error. This will ensure that the erroneous socket is closed and cleaned up by the web server.

  - Presently Chunked Encoding is not supported

  Parameters:

    - r -- [in] The request being responded to

    - buf -- [in] Pointer to a buffer that the data will be read into

    - buf_len -- [in] Length of the buffer

  Returns:

    - Bytes : Number of bytes read into the buffer successfully

    - 0 : Buffer length parameter is zero / connection closed by peer

    - HTTPD_SOCK_ERR_INVALID : Invalid arguments

    - HTTPD_SOCK_ERR_TIMEOUT : Timeout/interrupted while calling socket recv()

    - HTTPD_SOCK_ERR_FAIL : Unrecoverable error while calling socket recv()

size_t httpd_req_get_hdr_value_len(httpd_req_t *r, const char *field)

  Search for a field in request headers and return the string length of it's value.

  Note

  - This API is supposed to be called only from the context of a URI handler where httpd_req_t* request pointer is valid.

  - Once httpd_resp_send() API is called all request headers are purged, so request headers need be copied into separate buffers if they are required later.

  Parameters:

    - r -- [in] The request being responded to

    - field -- [in] The header field to be searched in the request

  Returns:

    - Length : If field is found in the request URL

    - Zero : Field not found / Invalid request / Null arguments

esp_err_t httpd_req_get_hdr_value_str(httpd_req_t *r, const char *field, char *val, size_t val_size)

  Get the value string of a field from the request headers.

  Note

  - This API is supposed to be called only from the context of a URI handler where httpd_req_t* request pointer is valid.

  - Once httpd_resp_send() API is called all request headers are purged, so request headers need be copied into separate buffers if they are required later.

  - If output size is greater than input, then the value is truncated, accompanied by truncation error as return value.

  - Use httpd_req_get_hdr_value_len() to know the right buffer length

  Parameters:

    - r -- [in] The request being responded to

    - field -- [in] The field to be searched in the header

    - val -- [out] Pointer to the buffer into which the value will be copied if the field is found

    - val_size -- [in] Size of the user buffer "val"

  Returns:

    - ESP_OK : Field found in the request header and value string copied

    - ESP_ERR_NOT_FOUND : Key not found

    - ESP_ERR_INVALID_ARG : Null arguments

    - ESP_ERR_HTTPD_INVALID_REQ : Invalid HTTP request pointer

    - ESP_ERR_HTTPD_RESULT_TRUNC : Value string truncated

size_t httpd_req_get_url_query_len(httpd_req_t *r)

  Get Query string length from the request URL.

  Note

  This API is supposed to be called only from the context of a URI handler where httpd_req_t* request pointer is valid

  Parameters:

    r -- [in] The request being responded to

  Returns:

    - Length : Query is found in the request URL

    - Zero : Query not found / Null arguments / Invalid request / uri is empty

esp_err_t httpd_req_get_url_query_str(httpd_req_t *r, char *buf, size_t buf_len)

  Get Query string from the request URL.

  Note

  - Presently, the user can fetch the full URL query string, but decoding will have to be performed by the user. Request headers can be read using httpd_req_get_hdr_value_str() to know the 'Content-Type' (eg. Content-Type: application/x-www-form-urlencoded) and then the appropriate decoding algorithm needs to be applied.

  - This API is supposed to be called only from the context of a URI handler where httpd_req_t* request pointer is valid

  - If output size is greater than input, then the value is truncated, accompanied by truncation error as return value

  - Prior to calling this function, one can use httpd_req_get_url_query_len() to know the query string length beforehand and hence allocate the buffer of right size (usually query string length + 1 for null termination) for storing the query string

  Parameters:

    - r -- [in] The request being responded to

    - buf -- [out] Pointer to the buffer into which the query string will be copied (if found)

    - buf_len -- [in] Length of output buffer

  Returns:

    - ESP_OK : Query is found in the request URL and copied to buffer

    - ESP_FAIL : uri is empty

    - ESP_ERR_NOT_FOUND : Query not found

    - ESP_ERR_INVALID_ARG : Null arguments

    - ESP_ERR_HTTPD_INVALID_REQ : Invalid HTTP request pointer

    - ESP_ERR_HTTPD_RESULT_TRUNC : Query string truncated

esp_err_t httpd_query_key_value(const char *qry, const char *key, char *val, size_t val_size)

  Helper function to get a URL query tag from a query string of the type param1=val1&param2=val2.

  Note

  - The components of URL query string (keys and values) are not URLdecoded. The user must check for 'Content-Type' field in the request headers and then depending upon the specified encoding (URLencoded or otherwise) apply the appropriate decoding algorithm.

  - If actual value size is greater than val_size, then the value is truncated, accompanied by truncation error as return value.

  Parameters:

    - qry -- [in] Pointer to query string

    - key -- [in] The key to be searched in the query string

    - val -- [out] Pointer to the buffer into which the value will be copied if the key is found

    - val_size -- [in] Size of the user buffer "val"

  Returns:

    - ESP_OK : Key is found in the URL query string and copied to buffer

    - ESP_ERR_NOT_FOUND : Key not found

    - ESP_ERR_INVALID_ARG : Null arguments

    - ESP_ERR_HTTPD_RESULT_TRUNC : Value string truncated

esp_err_t httpd_req_get_cookie_val(httpd_req_t *req, const char *cookie_name, char *val, size_t *val_size)

  Get the value string of a cookie value from the "Cookie" request headers by cookie name.

  Parameters:

    - req -- [in] Pointer to the HTTP request

    - cookie_name -- [in] The cookie name to be searched in the request

    - val -- [out] Pointer to the buffer into which the value of cookie will be copied if the cookie is found

    - val_size -- [inout] Pointer to size of the user buffer "val". This variable will contain cookie length if ESP_OK is returned and required buffer length in case ESP_ERR_HTTPD_RESULT_TRUNC is returned.

  Returns:

    - ESP_OK : Key is found in the cookie string and copied to buffer

    - ESP_ERR_NOT_FOUND : Key not found

    - ESP_ERR_INVALID_ARG : Null arguments

    - ESP_ERR_HTTPD_RESULT_TRUNC : Value string truncated

    - ESP_ERR_NO_MEM : Memory allocation failure

bool httpd_uri_match_wildcard(const char *uri_template, const char *uri_to_match, size_t match_upto)

  Test if a URI matches the given wildcard template.

  Template may end with '?' to make the previous character optional (typically a slash), '*' for a wildcard match, and '?*' to make the previous character optional, and if present, allow anything to follow.

  Example:

  - * matches everything

  - /api/? matches /api and /api/

  - /api/* (sans the backslash) matches /api/ and /api/status, but not /api or /ap

  - /api/?* or /api/*? (sans the backslash) matches /api/, /api/status, and also /api, but not /apix or /ap

  The special characters '?' and '*' anywhere else in the template will be taken literally.

  Parameters:

    - uri_template -- [in] URI template (pattern)

    - uri_to_match -- [in] URI to be matched

    - match_upto -- [in] how many characters of the URI buffer to test (there may be trailing query string etc.)

  Returns:

    true if a match was found

esp_err_t httpd_resp_send(httpd_req_t *r, const char *buf, ssize_t buf_len)

  API to send a complete HTTP response.

  This API will send the data as an HTTP response to the request. This assumes that you have the entire response ready in a single buffer. If you wish to send response in incremental chunks use httpd_resp_send_chunk() instead.

  If no status code and content-type were set, by default this will send 200 OK status code and content type as text/html. You may call the following functions before this API to configure the response headers : httpd_resp_set_status() - for setting the HTTP status string, httpd_resp_set_type() - for setting the Content Type, httpd_resp_set_hdr() - for appending any additional field value entries in the response header

  Note

  - This API is supposed to be called only from the context of a URI handler where httpd_req_t* request pointer is valid.

  - Once this API is called, the request has been responded to.

  - No additional data can then be sent for the request.

  - Once this API is called, all request headers are purged, so request headers need be copied into separate buffers if they are required later.

  Parameters:

    - r -- [in] The request being responded to

    - buf -- [in] Buffer from where the content is to be fetched

    - buf_len -- [in] Length of the buffer, HTTPD_RESP_USE_STRLEN to use strlen()

  Returns:

    - ESP_OK : On successfully sending the response packet

    - ESP_ERR_INVALID_ARG : Null request pointer

    - ESP_ERR_HTTPD_RESP_HDR : Essential headers are too large for internal buffer

    - ESP_ERR_HTTPD_RESP_SEND : Error in raw send

    - ESP_ERR_HTTPD_INVALID_REQ : Invalid request

esp_err_t httpd_resp_send_chunk(httpd_req_t *r, const char *buf, ssize_t buf_len)

  API to send one HTTP chunk.

  This API will send the data as an HTTP response to the request. This API will use chunked-encoding and send the response in the form of chunks. If you have the entire response contained in a single buffer, please use httpd_resp_send() instead.

  If no status code and content-type were set, by default this will send 200 OK status code and content type as text/html. You may call the following functions before this API to configure the response headers httpd_resp_set_status() - for setting the HTTP status string, httpd_resp_set_type() - for setting the Content Type, httpd_resp_set_hdr() - for appending any additional field value entries in the response header

  Note

  - This API is supposed to be called only from the context of a URI handler where httpd_req_t* request pointer is valid.

  - When you are finished sending all your chunks, you must call this function with buf_len as 0.

  - Once this API is called, all request headers are purged, so request headers need be copied into separate buffers if they are required later.

  Parameters:

    - r -- [in] The request being responded to

    - buf -- [in] Pointer to a buffer that stores the data

    - buf_len -- [in] Length of the buffer, HTTPD_RESP_USE_STRLEN to use strlen()

  Returns:

    - ESP_OK : On successfully sending the response packet chunk

    - ESP_ERR_INVALID_ARG : Null request pointer

    - ESP_ERR_HTTPD_RESP_HDR : Essential headers are too large for internal buffer

    - ESP_ERR_HTTPD_RESP_SEND : Error in raw send

    - ESP_ERR_HTTPD_INVALID_REQ : Invalid request pointer

static inline esp_err_t httpd_resp_sendstr(httpd_req_t *r, const char *str)

  API to send a complete string as HTTP response.

  This API simply calls httpd_resp_send with buffer length set to string length assuming the buffer contains a null terminated string

  Parameters:

    - r -- [in] The request being responded to

    - str -- [in] String to be sent as response body

  Returns:

    - ESP_OK : On successfully sending the response packet

    - ESP_ERR_INVALID_ARG : Null request pointer

    - ESP_ERR_HTTPD_RESP_HDR : Essential headers are too large for internal buffer

    - ESP_ERR_HTTPD_RESP_SEND : Error in raw send

    - ESP_ERR_HTTPD_INVALID_REQ : Invalid request

static inline esp_err_t httpd_resp_sendstr_chunk(httpd_req_t *r, const char *str)

  API to send a string as an HTTP response chunk.

  This API simply calls httpd_resp_send_chunk with buffer length set to string length assuming the buffer contains a null terminated string

  Parameters:

    - r -- [in] The request being responded to

    - str -- [in] String to be sent as response body (NULL to finish response packet)

  Returns:

    - ESP_OK : On successfully sending the response packet

    - ESP_ERR_INVALID_ARG : Null request pointer

    - ESP_ERR_HTTPD_RESP_HDR : Essential headers are too large for internal buffer

    - ESP_ERR_HTTPD_RESP_SEND : Error in raw send

    - ESP_ERR_HTTPD_INVALID_REQ : Invalid request

esp_err_t httpd_resp_set_status(httpd_req_t *r, const char *status)

  API to set the HTTP status code.

  This API sets the status of the HTTP response to the value specified. By default, the '200 OK' response is sent as the response.

  Note

  - This API is supposed to be called only from the context of a URI handler where httpd_req_t* request pointer is valid.

  - This API only sets the status to this value. The status isn't sent out until any of the send APIs is executed.

  - Make sure that the lifetime of the status string is valid till send function is called.

  Parameters:

    - r -- [in] The request being responded to

    - status -- [in] The HTTP status code of this response

  Returns:

    - ESP_OK : On success

    - ESP_ERR_INVALID_ARG : Null arguments

    - ESP_ERR_HTTPD_INVALID_REQ : Invalid request pointer

esp_err_t httpd_resp_set_type(httpd_req_t *r, const char *type)

  API to set the HTTP content type.

  This API sets the 'Content Type' field of the response. The default content type is 'text/html'.

  Note

  - This API is supposed to be called only from the context of a URI handler where httpd_req_t* request pointer is valid.

  - This API only sets the content type to this value. The type isn't sent out until any of the send APIs is executed.

  - Make sure that the lifetime of the type string is valid till send function is called.

  Parameters:

    - r -- [in] The request being responded to

    - type -- [in] The Content Type of the response

  Returns:

    - ESP_OK : On success

    - ESP_ERR_INVALID_ARG : Null arguments

    - ESP_ERR_HTTPD_INVALID_REQ : Invalid request pointer

esp_err_t httpd_resp_set_hdr(httpd_req_t *r, const char *field, const char *value)

  API to append any additional headers.

  This API sets any additional header fields that need to be sent in the response.

  Note

  - This API is supposed to be called only from the context of a URI handler where httpd_req_t* request pointer is valid.

  - The header isn't sent out until any of the send APIs is executed.

  - The maximum allowed number of additional headers is limited to value of max_resp_headers in config structure.

  - Make sure that the lifetime of the field value strings are valid till send function is called.

  Parameters:

    - r -- [in] The request being responded to

    - field -- [in] The field name of the HTTP header

    - value -- [in] The value of this HTTP header

  Returns:

    - ESP_OK : On successfully appending new header

    - ESP_ERR_INVALID_ARG : Null arguments

    - ESP_ERR_HTTPD_RESP_HDR : Total additional headers exceed max allowed

    - ESP_ERR_HTTPD_INVALID_REQ : Invalid request pointer

esp_err_t httpd_resp_send_err(httpd_req_t *req, httpd_err_code_t error, const char *msg)

  For sending out error code in response to HTTP request.

  Note

  - This API is supposed to be called only from the context of a URI handler where httpd_req_t* request pointer is valid.

  - Once this API is called, all request headers are purged, so request headers need be copied into separate buffers if they are required later.

  - If you wish to send additional data in the body of the response, please use the lower-level functions directly.

  Parameters:

    - req -- [in] Pointer to the HTTP request for which the response needs to be sent

    - error -- [in] Error type to send

    - msg -- [in] Error message string (pass NULL for default message)

  Returns:

    - ESP_OK : On successfully sending the response packet

    - ESP_ERR_INVALID_ARG : Null arguments

    - ESP_ERR_HTTPD_RESP_SEND : Error in raw send

    - ESP_ERR_HTTPD_INVALID_REQ : Invalid request pointer

esp_err_t httpd_resp_send_custom_err(httpd_req_t *req, const char *status, const char *msg)

  For sending out custom error code in response to HTTP request.

  Note

  - This API is supposed to be called only from the context of a URI handler where httpd_req_t* request pointer is valid.

  - Once this API is called, all request headers are purged, so request headers need be copied into separate buffers if they are required later.

  - If you wish to send additional data in the body of the response, please use the lower-level functions directly.

  Parameters:

    - req -- [in] Pointer to the HTTP request for which the response needs to be sent

    - status -- [in] Error status to send

    - msg -- [in] Error message string

  Returns:

    - ESP_OK : On successfully sending the response packet

    - ESP_ERR_INVALID_ARG : Null arguments

    - ESP_ERR_HTTPD_RESP_SEND : Error in raw send

    - ESP_ERR_HTTPD_INVALID_REQ : Invalid request pointer

static inline esp_err_t httpd_resp_send_404(httpd_req_t *r)

  Helper function for HTTP 404.

  Send HTTP 404 message. If you wish to send additional data in the body of the response, please use the lower-level functions directly.

  Note

  - This API is supposed to be called only from the context of a URI handler where httpd_req_t* request pointer is valid.

  - Once this API is called, all request headers are purged, so request headers need be copied into separate buffers if they are required later.

  Parameters:

    r -- [in] The request being responded to

  Returns:

    - ESP_OK : On successfully sending the response packet

    - ESP_ERR_INVALID_ARG : Null arguments

    - ESP_ERR_HTTPD_RESP_SEND : Error in raw send

    - ESP_ERR_HTTPD_INVALID_REQ : Invalid request pointer

static inline esp_err_t httpd_resp_send_408(httpd_req_t *r)

  Helper function for HTTP 408.

  Send HTTP 408 message. If you wish to send additional data in the body of the response, please use the lower-level functions directly.

  Note

  - This API is supposed to be called only from the context of a URI handler where httpd_req_t* request pointer is valid.

  - Once this API is called, all request headers are purged, so request headers need be copied into separate buffers if they are required later.

  Parameters:

    r -- [in] The request being responded to

  Returns:

    - ESP_OK : On successfully sending the response packet

    - ESP_ERR_INVALID_ARG : Null arguments

    - ESP_ERR_HTTPD_RESP_SEND : Error in raw send

    - ESP_ERR_HTTPD_INVALID_REQ : Invalid request pointer

static inline esp_err_t httpd_resp_send_500(httpd_req_t *r)

  Helper function for HTTP 500.

  Send HTTP 500 message. If you wish to send additional data in the body of the response, please use the lower-level functions directly.

  Note

  - This API is supposed to be called only from the context of a URI handler where httpd_req_t* request pointer is valid.

  - Once this API is called, all request headers are purged, so request headers need be copied into separate buffers if they are required later.

  Parameters:

    r -- [in] The request being responded to

  Returns:

    - ESP_OK : On successfully sending the response packet

    - ESP_ERR_INVALID_ARG : Null arguments

    - ESP_ERR_HTTPD_RESP_SEND : Error in raw send

    - ESP_ERR_HTTPD_INVALID_REQ : Invalid request pointer

int httpd_send(httpd_req_t *r, const char *buf, size_t buf_len)

  Raw HTTP send.

  Call this API if you wish to construct your custom response packet. When using this, all essential header, eg. HTTP version, Status Code, Content Type and Length, Encoding, etc. will have to be constructed manually, and HTTP delimiters (CRLF) will need to be placed correctly for separating sub-sections of the HTTP response packet.

  If the send override function is set, this API will end up calling that function eventually to send data out.

  Note

  - This API is supposed to be called only from the context of a URI handler where httpd_req_t* request pointer is valid.

  - Unless the response has the correct HTTP structure (which the user must now ensure) it is not guaranteed that it will be recognized by the client. For most cases, you wouldn't have to call this API, but you would rather use either of : httpd_resp_send(), httpd_resp_send_chunk()

  Parameters:

    - r -- [in] The request being responded to

    - buf -- [in] Buffer from where the fully constructed packet is to be read

    - buf_len -- [in] Length of the buffer

  Returns:

    - Bytes : Number of bytes that were sent successfully

    - HTTPD_SOCK_ERR_INVALID : Invalid arguments

    - HTTPD_SOCK_ERR_TIMEOUT : Timeout/interrupted while calling socket send()

    - HTTPD_SOCK_ERR_FAIL : Unrecoverable error while calling socket send()

int httpd_socket_send(httpd_handle_t hd, int sockfd, const char *buf, size_t buf_len, int flags)

  A low level API to send data on a given socket

  This internally calls the default send function, or the function registered by httpd_sess_set_send_override().

  Note

  This API is not recommended to be used in any request handler. Use this only for advanced use cases, wherein some asynchronous data is to be sent over a socket.

  Parameters:

    - hd -- [in] server instance

    - sockfd -- [in] session socket file descriptor

    - buf -- [in] buffer with bytes to send

    - buf_len -- [in] data size

    - flags -- [in] flags for the send() function

  Returns:

    - Bytes : The number of bytes sent successfully

    - HTTPD_SOCK_ERR_INVALID : Invalid arguments

    - HTTPD_SOCK_ERR_TIMEOUT : Timeout/interrupted while calling socket send()

    - HTTPD_SOCK_ERR_FAIL : Unrecoverable error while calling socket send()

int httpd_socket_recv(httpd_handle_t hd, int sockfd, char *buf, size_t buf_len, int flags)

  A low level API to receive data from a given socket

  This internally calls the default recv function, or the function registered by httpd_sess_set_recv_override().

  Note

  This API is not recommended to be used in any request handler. Use this only for advanced use cases, wherein some asynchronous communication is required.

  Parameters:

    - hd -- [in] server instance

    - sockfd -- [in] session socket file descriptor

    - buf -- [in] buffer with bytes to send

    - buf_len -- [in] data size

    - flags -- [in] flags for the send() function

  Returns:

    - Bytes : The number of bytes received successfully

    - 0 : Buffer length parameter is zero / connection closed by peer

    - HTTPD_SOCK_ERR_INVALID : Invalid arguments

    - HTTPD_SOCK_ERR_TIMEOUT : Timeout/interrupted while calling socket recv()

    - HTTPD_SOCK_ERR_FAIL : Unrecoverable error while calling socket recv()

esp_err_t httpd_register_err_handler(httpd_handle_t handle, httpd_err_code_t error, httpd_err_handler_func_t handler_fn)

  Function for registering HTTP error handlers.

  This function maps a handler function to any supported error code given by `httpd_err_code_t`. See prototype `httpd_err_handler_func_t` above for details.

  Parameters:

    - handle -- [in] HTTP server handle

    - error -- [in] Error type

    - handler_fn -- [in] User implemented handler function (Pass NULL to unset any previously set handler)

  Returns:

    - ESP_OK : handler registered successfully

    - ESP_ERR_INVALID_ARG : invalid error code or server handle

esp_err_t httpd_ws_recv_frame(httpd_req_t *req, httpd_ws_frame_t *pkt, size_t max_len)

  Receive and parse a WebSocket frame.

  Note

  Calling httpd_ws_recv_frame() with max_len as 0 will give actual frame size in pkt->len. The user can dynamically allocate space for pkt->payload as per this length and call httpd_ws_recv_frame() again to get the actual data. Please refer to the corresponding example for usage.

  Parameters:

    - req -- [in] Current request

    - pkt -- [out] WebSocket packet

    - max_len -- [in] Maximum length for receive

  Returns:

    - 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_send_frame(httpd_req_t *req, httpd_ws_frame_t *pkt)

  Construct and send a WebSocket frame.

  Parameters:

    - req -- [in] Current request

    - pkt -- [in] WebSocket frame

  Returns:

    - 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_async(httpd_handle_t hd, int fd, httpd_ws_frame_t *frame)

  Low level send of a WebSocket frame out of the scope of current request using internally configured httpd send function.

  This API should rarely be called directly, with an exception of asynchronous send using httpd_queue_work.

  Parameters:

    - hd -- [in] Server instance data

    - fd -- [in] Socket descriptor for sending data

    - frame -- [in] WebSocket frame

  Returns:

    - 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)

httpd_ws_client_info_t httpd_ws_get_fd_info(httpd_handle_t hd, int fd)

  Checks the supplied socket descriptor if it belongs to any active client of this server instance and if the websoket protocol is active.

  Parameters:

    - hd -- [in] Server instance data

    - fd -- [in] Socket descriptor

  Returns:

    - HTTPD_WS_CLIENT_INVALID : This fd is not a client of this httpd

    - HTTPD_WS_CLIENT_HTTP : This fd is an active client, protocol is not WS

    - HTTPD_WS_CLIENT_WEBSOCKET : This fd is an active client, protocol is WS

esp_err_t httpd_ws_send_data(httpd_handle_t handle, int socket, httpd_ws_frame_t *frame)

  Sends data to to specified websocket synchronously.

  Parameters:

    - handle -- [in] Server instance data

    - socket -- [in] Socket descriptor

    - frame -- [in] Websocket frame

  Returns:

    - ESP_OK : On successful

    - ESP_FAIL : When socket errors occurs

    - ESP_ERR_NO_MEM : Unable to allocate memory

esp_err_t httpd_ws_send_data_async(httpd_handle_t handle, int socket, httpd_ws_frame_t *frame, transfer_complete_cb callback, void *arg)

  Sends data to to specified websocket asynchronously.

  Parameters:

    - handle -- [in] Server instance data

    - socket -- [in] Socket descriptor

    - frame -- [in] Websocket frame

    - callback -- [in] Callback invoked after sending data

    - arg -- [in] User data passed to provided callback

  Returns:

    - ESP_OK : On successful

    - ESP_FAIL : When socket errors occurs

    - ESP_ERR_NO_MEM : Unable to allocate memory

esp_err_t httpd_register_uri_handler(httpd_handle_t handle, const httpd_uri_t *uri_handler)

  Registers a URI handler.

  Example usage:

      esp_err_t my_uri_handler(httpd_req_t* req)
      {
      // Recv , Process and Send
          ....
          ....
          ....

      // Fail condition
      if (....) {
      // Return fail to close session //
      return ESP_FAIL;
          }

      // On success
      return ESP_OK;
      }

      // URI handler structure
      httpd_uri_t my_uri {
          .uri      = "/my_uri/path/xyz",
          .method   = HTTP_GET,
          .handler  = my_uri_handler,
          .user_ctx = NULL
      };

      // Register handler
      if (httpd_register_uri_handler(server_handle, &my_uri) != ESP_OK) {
      // If failed to register handler
         ....
      }

  Note

  URI handlers can be registered in real time as long as the server handle is valid.

  Parameters:

    - handle -- [in] handle to HTTPD server instance

    - uri_handler -- [in] pointer to handler that needs to be registered

  Returns:

    - ESP_OK : On successfully registering the handler

    - ESP_ERR_INVALID_ARG : Null arguments

    - ESP_ERR_HTTPD_HANDLERS_FULL : If no slots left for new handler

    - ESP_ERR_HTTPD_HANDLER_EXISTS : If handler with same URI and method is already registered

esp_err_t httpd_unregister_uri_handler(httpd_handle_t handle, const char *uri, httpd_method_t method)

  Unregister a URI handler.

  Parameters:

    - handle -- [in] handle to HTTPD server instance

    - uri -- [in] URI string

    - method -- [in] HTTP method

  Returns:

    - ESP_OK : On successfully deregistering the handler

    - ESP_ERR_INVALID_ARG : Null arguments

    - ESP_ERR_NOT_FOUND : Handler with specified URI and method not found

esp_err_t httpd_unregister_uri(httpd_handle_t handle, const char *uri)

  Unregister all URI handlers with the specified uri string.

  Parameters:

    - handle -- [in] handle to HTTPD server instance

    - uri -- [in] uri string specifying all handlers that need to be deregisterd

  Returns:

    - ESP_OK : On successfully deregistering all such handlers

    - ESP_ERR_INVALID_ARG : Null arguments

    - ESP_ERR_NOT_FOUND : No handler registered with specified uri string

esp_err_t httpd_queue_work(httpd_handle_t handle, httpd_work_fn_t work, void *arg)

  Queue execution of a function in HTTPD's context.

  This API queues a work function for asynchronous execution

  Note

  Some protocols require that the web server generate some asynchronous data and send it to the persistently opened connection. This facility is for use by such protocols.

  Parameters:

    - handle -- [in] Handle to server returned by httpd_start

    - work -- [in] Pointer to the function to be executed in the HTTPD's context

    - arg -- [in] Pointer to the arguments that should be passed to this function

  Returns:

    - ESP_OK : On successfully queueing the work

    - ESP_FAIL : Failure in ctrl socket

    - ESP_ERR_INVALID_ARG : Null arguments

void *httpd_sess_get_ctx(httpd_handle_t handle, int sockfd)

  Get session context from socket descriptor.

  Typically if a session context is created, it is available to URI handlers through the httpd_req_t structure. But, there are cases where the web server's send/receive functions may require the context (for example, for accessing keying information etc). Since the send/receive function only have the socket descriptor at their disposal, this API provides them with a way to retrieve the session context.

  Parameters:

    - handle -- [in] Handle to server returned by httpd_start

    - sockfd -- [in] The socket descriptor for which the context should be extracted.

  Returns:

    - void* : Pointer to the context associated with this session

    - NULL : Empty context / Invalid handle / Invalid socket fd

void httpd_sess_set_ctx(httpd_handle_t handle, int sockfd, void *ctx, httpd_free_ctx_fn_t free_fn)

  Set session context by socket descriptor.

  Parameters:

    - handle -- [in] Handle to server returned by httpd_start

    - sockfd -- [in] The socket descriptor for which the context should be extracted.

    - ctx -- [in] Context object to assign to the session

    - free_fn -- [in] Function that should be called to free the context

void *httpd_sess_get_transport_ctx(httpd_handle_t handle, int sockfd)

  Get session 'transport' context by socket descriptor.

  This context is used by the send/receive functions, for example to manage SSL context.

  See also

  httpd_sess_get_ctx()

  Parameters:

    - handle -- [in] Handle to server returned by httpd_start

    - sockfd -- [in] The socket descriptor for which the context should be extracted.

  Returns:

    - void* : Pointer to the transport context associated with this session

    - NULL : Empty context / Invalid handle / Invalid socket fd

void httpd_sess_set_transport_ctx(httpd_handle_t handle, int sockfd, void *ctx, httpd_free_ctx_fn_t free_fn)

  Set session 'transport' context by socket descriptor.

  See also

  httpd_sess_set_ctx()

  Parameters:

    - handle -- [in] Handle to server returned by httpd_start

    - sockfd -- [in] The socket descriptor for which the context should be extracted.

    - ctx -- [in] Transport context object to assign to the session

    - free_fn -- [in] Function that should be called to free the transport context

void *httpd_get_global_user_ctx(httpd_handle_t handle)

  Get HTTPD global user context (it was set in the server config struct)

  Parameters:

    handle -- [in] Handle to server returned by httpd_start

  Returns:

    global user context

void *httpd_get_global_transport_ctx(httpd_handle_t handle)

  Get HTTPD global transport context (it was set in the server config struct)

  Parameters:

    handle -- [in] Handle to server returned by httpd_start

  Returns:

    global transport context

esp_err_t httpd_sess_trigger_close(httpd_handle_t handle, int sockfd)

  Trigger an httpd session close externally.

  Note

  Calling this API is only required in special circumstances wherein some application requires to close an httpd client session asynchronously.

  Parameters:

    - handle -- [in] Handle to server returned by httpd_start

    - sockfd -- [in] The socket descriptor of the session to be closed

  Returns:

    - ESP_OK : On successfully initiating closure

    - ESP_FAIL : Failure to queue work

    - ESP_ERR_NOT_FOUND : Socket fd not found

    - ESP_ERR_INVALID_ARG : Null arguments

esp_err_t httpd_sess_update_lru_counter(httpd_handle_t handle, int sockfd)

  Update LRU counter for a given socket.

  LRU Counters are internally associated with each session to monitor how recently a session exchanged traffic. When LRU purge is enabled, if a client is requesting for connection but maximum number of sockets/sessions is reached, then the session having the earliest LRU counter is closed automatically.

  Updating the LRU counter manually prevents the socket from being purged due to the Least Recently Used (LRU) logic, even though it might not have received traffic for some time. This is useful when all open sockets/session are frequently exchanging traffic but the user specifically wants one of the sessions to be kept open, irrespective of when it last exchanged a packet.

  Note

  Calling this API is only necessary if the LRU Purge Enable option is enabled.

  Parameters:

    - handle -- [in] Handle to server returned by httpd_start

    - sockfd -- [in] The socket descriptor of the session for which LRU counter is to be updated

  Returns:

    - ESP_OK : Socket found and LRU counter updated

    - ESP_ERR_NOT_FOUND : Socket not found

    - ESP_ERR_INVALID_ARG : Null arguments

esp_err_t httpd_get_client_list(httpd_handle_t handle, size_t *fds, int *client_fds)

  Returns list of current socket descriptors of active sessions.

  Note

  Size of provided array has to be equal or greater then maximum number of opened sockets, configured upon initialization with max_open_sockets field in httpd_config_t structure.

  Parameters:

    - handle -- [in] Handle to server returned by httpd_start

    - fds -- [inout] In: Size of provided client_fds array Out: Number of valid client fds returned in client_fds,

    - client_fds -- [out] Array of client fds

  Returns:

    - ESP_OK : Successfully retrieved session list

    - ESP_ERR_INVALID_ARG : Wrong arguments or list is longer than provided array

### Structures

struct esp_http_server_event_data

  Argument structure for HTTP_SERVER_EVENT_ON_DATA and HTTP_SERVER_EVENT_SENT_DATA event

  Public Members

  int fd

    Session socket file descriptor

  int data_len

    Data length

struct httpd_config

  HTTP Server Configuration Structure.

  Note

  Use HTTPD_DEFAULT_CONFIG() to initialize the configuration to a default value and then modify only those fields that are specifically determined by the use case.

  Public Members

  unsigned task_priority

    Priority of FreeRTOS task which runs the server

  size_t stack_size

    The maximum stack size allowed for the server task

  BaseType_t core_id

    The core the HTTP server task will run on

  uint32_t task_caps

    The memory capabilities to use when allocating the HTTP server task's stack

  size_t max_req_hdr_len

    Size limits for the header and URI buffers respectively. These are just limits, allocation would depend upon actual size of URI/header. Size limit for the header buffer (By default this value is set to CONFIG_HTTPD_MAX_REQ_HDR_LEN, overwrite is possible)

  size_t max_uri_len

    Size limit for the URI buffer By default this value is set to CONFIG_HTTPD_MAX_URI_LEN, overwrite is possible)

  uint16_t server_port

    TCP Port number for receiving and transmitting HTTP traffic

  uint16_t ctrl_port

    UDP Port number for asynchronously exchanging control signals between various components of the server

  uint16_t max_open_sockets

    Max number of sockets/clients connected at any time (3 sockets are reserved for internal working of the HTTP server)

  uint16_t max_uri_handlers

    Maximum allowed uri handlers

  uint16_t max_resp_headers

    Maximum allowed additional headers in HTTP response

  uint16_t backlog_conn

    Number of backlog connections

  bool lru_purge_enable

    Purge "Least Recently Used" connection

  uint16_t recv_wait_timeout

    Timeout for recv function (in seconds)

  uint16_t send_wait_timeout

    Timeout for send function (in seconds)

  void *global_user_ctx

    Global user context.

    This field can be used to store arbitrary user data within the server context. The value can be retrieved using the server handle, available e.g. in the httpd_req_t struct.

    When shutting down, the server frees up the user context by calling free() on the global_user_ctx field. If you wish to use a custom function for freeing the global user context, please specify that here.

  httpd_free_ctx_fn_t global_user_ctx_free_fn

    Free function for global user context

  void *global_transport_ctx

    Global transport context.

    Similar to global_user_ctx, but used for session encoding or encryption (e.g. to hold the SSL context). It will be freed using free(), unless global_transport_ctx_free_fn is specified.

  httpd_free_ctx_fn_t global_transport_ctx_free_fn

    Free function for global transport context

  bool enable_so_linger

    bool to enable/disable linger

  int linger_timeout

    linger timeout (in seconds)

  bool keep_alive_enable

    Enable keep-alive timeout

  int keep_alive_idle

    Keep-alive idle time. Default is 5 (second)

  int keep_alive_interval

    Keep-alive interval time. Default is 5 (second)

  int keep_alive_count

    Keep-alive packet retry send count. Default is 3 counts

  httpd_open_func_t open_fn

    Custom session opening callback.

    Called on a new session socket just after accept(), but before reading any data.

    This is an opportunity to set up e.g. SSL encryption using global_transport_ctx and the send/recv/pending session overrides.

    If a context needs to be maintained between these functions, store it in the session using httpd_sess_set_transport_ctx() and retrieve it later with httpd_sess_get_transport_ctx()

    Returning a value other than ESP_OK will immediately close the new socket.

  httpd_close_func_t close_fn

    Custom session closing callback.

    Called when a session is deleted, before freeing user and transport contexts and before closing the socket. This is a place for custom de-init code common to all sockets.

    The server will only close the socket if no custom session closing callback is set. If a custom callback is used, `close(sockfd)` should be called in here for most cases.

    Set the user or transport context to NULL if it was freed here, so the server does not try to free it again.

    This function is run for all terminated sessions, including sessions where the socket was closed by the network stack - that is, the file descriptor may not be valid anymore.

  httpd_uri_match_func_t uri_match_fn

    URI matcher function.

    Called when searching for a matching URI: 1) whose request handler is to be executed right after an HTTP request is successfully parsed 2) in order to prevent duplication while registering a new URI handler using `httpd_register_uri_handler()`

    Available options are: 1) NULL : Internally do basic matching using `strncmp()` 2) `httpd_uri_match_wildcard()` : URI wildcard matcher

    Users can implement their own matching functions (See description of the `httpd_uri_match_func_t` function prototype)

struct httpd_req

  HTTP Request Data Structure.

  Public Members

  httpd_handle_t handle

    Handle to server instance

  int method

    The type of HTTP request, -1 if unsupported method, HTTP_ANY for wildcard method to support every method

  const char uri[512 + 1]

    The URI of this request (1 byte extra for null termination)

  size_t content_len

    Length of the request body

  void *aux

    Internally used members

  void *user_ctx

    User context pointer passed during URI registration.

  void *sess_ctx

    Session Context Pointer

    A session context. Contexts are maintained across 'sessions' for a given open TCP connection. One session could have multiple request responses. The web server will ensure that the context persists across all these request and responses.

    By default, this is NULL. URI Handlers can set this to any meaningful value.

    If the underlying socket gets closed, and this pointer is non-NULL, the web server will free up the context by calling free(), unless free_ctx function is set.

  httpd_free_ctx_fn_t free_ctx

    Pointer to free context hook

    Function to free session context

    If the web server's socket closes, it frees up the session context by calling free() on the sess_ctx member. If you wish to use a custom function for freeing the session context, please specify that here.

  bool ignore_sess_ctx_changes

    Flag indicating if Session Context changes should be ignored

    By default, if you change the sess_ctx in some URI handler, the http server will internally free the earlier context (if non NULL), after the URI handler returns. If you want to manage the allocation/reallocation/freeing of sess_ctx yourself, set this flag to true, so that the server will not perform any checks on it. The context will be cleared by the server (by calling free_ctx or free()) only if the socket gets closed.

struct httpd_uri

  Structure for URI handler.

  Public Members

  const char *uri

    The URI to handle

  httpd_method_t method

    Method supported by the URI, HTTP_ANY for wildcard method to support all methods

  esp_err_t (*handler)(httpd_req_t *r)

    Handler to call for supported request method. This must return ESP_OK, or else the underlying socket will be closed.

  void *user_ctx

    Pointer to user context data which will be available to handler

  bool is_websocket

    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 handle_ws_control_frames

    Flag indicating that control frames (PING, PONG, CLOSE) are also passed to the handler This is used if a custom processing of the control frames is needed

  const char *supported_subprotocol

    Pointer to subprotocol supported by URI

  esp_err_t (*ws_pre_handshake_cb)(httpd_req_t *req)

    Pointer to WebSocket pre-handshake callback. This will be called before the WebSocket handshake is processed, i.e. before the server responds with the WebSocket handshake response or before switching to the WebSocket handler.

struct httpd_ws_frame

  WebSocket frame format.

  Public Members

  bool final

    Final frame: For received frames this field indicates whether the `FIN` flag was set. For frames to be transmitted, this field is only used if the `fragmented` option is set as well. If `fragmented` is false, the `FIN` flag is set by default, marking the ws_frame as a complete/unfragmented message (esp_http_server doesn't automatically fragment messages)

  bool fragmented

    Indication that the frame allocated for transmission is a message fragment, so the `FIN` flag is set manually according to the `final` option. This flag is never set for received messages

  httpd_ws_type_t type

    WebSocket frame type

  uint8_t *payload

    Pre-allocated data buffer

  size_t len

    Length of the WebSocket data

### Macros

HTTP_ANY

HTTPD_SOCK_ERR_FAIL

HTTPD_SOCK_ERR_INVALID

HTTPD_SOCK_ERR_TIMEOUT

HTTPD_200

  HTTP Response 200

HTTPD_204

  HTTP Response 204

HTTPD_207

  HTTP Response 207

HTTPD_400

  HTTP Response 400

HTTPD_404

  HTTP Response 404

HTTPD_408

  HTTP Response 408

HTTPD_500

  HTTP Response 500

HTTPD_TYPE_JSON

  HTTP Content type JSON

HTTPD_TYPE_TEXT

  HTTP Content type text/HTML

HTTPD_TYPE_OCTET

  HTTP Content type octext-stream

ESP_HTTPD_DEF_CTRL_PORT

  HTTP Server control socket port

HTTPD_DEFAULT_CONFIG()

ESP_ERR_HTTPD_BASE

  Starting number of HTTPD error codes

ESP_ERR_HTTPD_HANDLERS_FULL

  All slots for registering URI handlers have been consumed

ESP_ERR_HTTPD_HANDLER_EXISTS

  URI handler with same method and target URI already registered

ESP_ERR_HTTPD_INVALID_REQ

  Invalid request pointer

ESP_ERR_HTTPD_RESULT_TRUNC

  Result string truncated

ESP_ERR_HTTPD_RESP_HDR

  Response header field larger than supported

ESP_ERR_HTTPD_RESP_SEND

  Error occurred while sending response packet

ESP_ERR_HTTPD_ALLOC_MEM

  Failed to dynamically allocate memory for resource

ESP_ERR_HTTPD_TASK

  Failed to launch server task/thread

HTTPD_RESP_USE_STRLEN

### Type Definitions

typedef void *httpd_handle_t

  HTTP Server Instance Handle.

  Every instance of the server will have a unique handle.

typedef enum http_method httpd_method_t

  HTTP Method Type wrapper over "enum http_method" available in "http_parser" library.

typedef void (*httpd_free_ctx_fn_t)(void *ctx)

  Prototype for freeing context data (if any)

  Param ctx:

    [in] object to free

typedef esp_err_t (*httpd_open_func_t)(httpd_handle_t hd, int sockfd)

  Function prototype for opening a session.

  Called immediately after the socket was opened to set up the send/recv functions and other parameters of the socket.

  Param hd:

    [in] server instance

  Param sockfd:

    [in] session socket file descriptor

  Return:

    - ESP_OK : On success

    - Any value other than ESP_OK will signal the server to close the socket immediately

typedef void (*httpd_close_func_t)(httpd_handle_t hd, int sockfd)

  Function prototype for closing a session.

  Note

  It's possible that the socket descriptor is invalid at this point, the function is called for all terminated sessions. Ensure proper handling of return codes.

  Param hd:

    [in] server instance

  Param sockfd:

    [in] session socket file descriptor

typedef bool (*httpd_uri_match_func_t)(const char *reference_uri, const char *uri_to_match, size_t match_upto)

  Function prototype for URI matching.

  Param reference_uri:

    [in] URI/template with respect to which the other URI is matched

  Param uri_to_match:

    [in] URI/template being matched to the reference URI/template

  Param match_upto:

    [in] For specifying the actual length of `uri_to_match` up to which the matching algorithm is to be applied (The maximum value is `strlen(uri_to_match)`, independent of the length of `reference_uri`)

  Return:

    true on match

typedef struct httpd_config httpd_config_t

  HTTP Server Configuration Structure.

  Note

  Use HTTPD_DEFAULT_CONFIG() to initialize the configuration to a default value and then modify only those fields that are specifically determined by the use case.

typedef int (*httpd_send_func_t)(httpd_handle_t hd, int sockfd, const char *buf, size_t buf_len, int flags)

  Prototype for HTTPDs low-level send function.

  Note

  User specified send function must handle errors internally, depending upon the set value of errno, and return specific HTTPD_SOCK_ERR_ codes, which will eventually be conveyed as return value of httpd_send() function

  Param hd:

    [in] server instance

  Param sockfd:

    [in] session socket file descriptor

  Param buf:

    [in] buffer with bytes to send

  Param buf_len:

    [in] data size

  Param flags:

    [in] flags for the send() function

  Return:

    - Bytes : The number of bytes sent successfully

    - HTTPD_SOCK_ERR_INVALID : Invalid arguments

    - HTTPD_SOCK_ERR_TIMEOUT : Timeout/interrupted while calling socket send()

    - HTTPD_SOCK_ERR_FAIL : Unrecoverable error while calling socket send()

typedef int (*httpd_recv_func_t)(httpd_handle_t hd, int sockfd, char *buf, size_t buf_len, int flags)

  Prototype for HTTPDs low-level recv function.

  Note

  User specified recv function must handle errors internally, depending upon the set value of errno, and return specific HTTPD_SOCK_ERR_ codes, which will eventually be conveyed as return value of httpd_req_recv() function

  Param hd:

    [in] server instance

  Param sockfd:

    [in] session socket file descriptor

  Param buf:

    [in] buffer with bytes to send

  Param buf_len:

    [in] data size

  Param flags:

    [in] flags for the send() function

  Return:

    - Bytes : The number of bytes received successfully

    - 0 : Buffer length parameter is zero / connection closed by peer

    - HTTPD_SOCK_ERR_INVALID : Invalid arguments

    - HTTPD_SOCK_ERR_TIMEOUT : Timeout/interrupted while calling socket recv()

    - HTTPD_SOCK_ERR_FAIL : Unrecoverable error while calling socket recv()

typedef int (*httpd_pending_func_t)(httpd_handle_t hd, int sockfd)

  Prototype for HTTPDs low-level "get pending bytes" function.

  Note

  User specified pending function must handle errors internally, depending upon the set value of errno, and return specific HTTPD_SOCK_ERR_ codes, which will be handled accordingly in the server task.

  Param hd:

    [in] server instance

  Param sockfd:

    [in] session socket file descriptor

  Return:

    - Bytes : The number of bytes waiting to be received

    - HTTPD_SOCK_ERR_INVALID : Invalid arguments

    - HTTPD_SOCK_ERR_TIMEOUT : Timeout/interrupted while calling socket pending()

    - HTTPD_SOCK_ERR_FAIL : Unrecoverable error while calling socket pending()

typedef esp_err_t (*httpd_err_handler_func_t)(httpd_req_t *req, httpd_err_code_t error)

  Function prototype for HTTP error handling.

  This function is executed upon HTTP errors generated during internal processing of an HTTP request. This is used to override the default behavior on error, which is to send HTTP error response and close the underlying socket.

  Note

  - If implemented, the server will not automatically send out HTTP error response codes, therefore, httpd_resp_send_err() must be invoked inside this function if user wishes to generate HTTP error responses.

  - When invoked, the validity of `uri`, `method`, `content_len` and `user_ctx` fields of the httpd_req_t parameter is not guaranteed as the HTTP request may be partially received/parsed.

  - The function must return ESP_OK if underlying socket needs to be kept open. Any other value will ensure that the socket is closed. The return value is ignored when error is of type `HTTPD_500_INTERNAL_SERVER_ERROR` and the socket closed anyway.

  Param req:

    [in] HTTP request for which the error needs to be handled

  Param error:

    [in] Error type

  Return:

    - ESP_OK : error handled successful

    - ESP_FAIL : failure indicates that the underlying socket needs to be closed

typedef struct httpd_ws_frame httpd_ws_frame_t

  WebSocket frame format.

typedef void (*transfer_complete_cb)(esp_err_t err, int socket, void *arg)

  Transfer complete callback.

typedef struct httpd_req httpd_req_t

  HTTP Request Data Structure.

typedef struct httpd_uri httpd_uri_t

  Structure for URI handler.

typedef void (*httpd_work_fn_t)(void *arg)

  Prototype of the HTTPD work function Please refer to httpd_queue_work() for more details.

  Param arg:

    [in] The arguments for this work function

### Enumerations

enum httpd_err_code_t

  Error codes sent as HTTP response in case of errors encountered during processing of an HTTP request.

  Values:

  enumerator HTTPD_500_INTERNAL_SERVER_ERROR
  enumerator HTTPD_501_METHOD_NOT_IMPLEMENTED
  enumerator HTTPD_505_VERSION_NOT_SUPPORTED
  enumerator HTTPD_400_BAD_REQUEST
  enumerator HTTPD_401_UNAUTHORIZED
  enumerator HTTPD_403_FORBIDDEN
  enumerator HTTPD_404_NOT_FOUND
  enumerator HTTPD_405_METHOD_NOT_ALLOWED
  enumerator HTTPD_408_REQ_TIMEOUT
  enumerator HTTPD_411_LENGTH_REQUIRED
  enumerator HTTPD_413_CONTENT_TOO_LARGE
  enumerator HTTPD_414_URI_TOO_LONG
  enumerator HTTPD_431_REQ_HDR_FIELDS_TOO_LARGE
  enumerator HTTPD_ERR_CODE_MAX

enum httpd_ws_type_t

  Enum for WebSocket packet types (Opcode in the header)

  Note

  Please refer to RFC6455 Section 5.4 for more details

  Values:

  enumerator HTTPD_WS_TYPE_CONTINUE
  enumerator HTTPD_WS_TYPE_TEXT
  enumerator HTTPD_WS_TYPE_BINARY
  enumerator HTTPD_WS_TYPE_CLOSE
  enumerator HTTPD_WS_TYPE_PING
  enumerator HTTPD_WS_TYPE_PONG

enum httpd_ws_client_info_t

  Enum for client info description.

  Values:

  enumerator HTTPD_WS_CLIENT_INVALID
  enumerator HTTPD_WS_CLIENT_HTTP
  enumerator HTTPD_WS_CLIENT_WEBSOCKET

enum esp_http_server_event_id_t

  HTTP Server events id.

  Values:

  enumerator HTTP_SERVER_EVENT_ERROR

    This event occurs when there are any errors during execution

  enumerator HTTP_SERVER_EVENT_START

    This event occurs when HTTP Server is started

  enumerator HTTP_SERVER_EVENT_ON_CONNECTED

    Once the HTTP Server has been connected to the client, no data exchange has been performed

  enumerator HTTP_SERVER_EVENT_ON_HEADER

    Occurs when receiving each header sent from the client

  enumerator HTTP_SERVER_EVENT_HEADERS_SENT

    After sending all the headers to the client

  enumerator HTTP_SERVER_EVENT_ON_DATA

    Occurs when receiving data from the client

  enumerator HTTP_SERVER_EVENT_SENT_DATA

    Occurs when an ESP HTTP server session is finished

  enumerator HTTP_SERVER_EVENT_DISCONNECTED

    The connection has been disconnected

  enumerator HTTP_SERVER_EVENT_STOP

    This event occurs when HTTP Server is stopped

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