ESP HTTP Client¶
Overview¶
esp_http_client
provides an API for making HTTP/S requests from ESP-IDF programs. The steps to use this API for an HTTP request are:
esp_http_client_init()
: To use the HTTP client, the first thing we must do is create anesp_http_client
by pass into this function with theesp_http_client_config_t
configurations. Which configuration values we do not define, the library will use default.esp_http_client_perform()
: Theesp_http_client
argument created from the init function is needed. This function performs all operations of the esp_http_client, from opening the connection, sending data, downloading data and closing the connection if necessary. All related events will be invoked in the event_handle (defined byesp_http_client_config_t
). This function performs its job and blocks the current task until it’s doneesp_http_client_cleanup()
: After completing our esp_http_client’s task, this is the last function to be called. It will close the connection (if any) and free up all the memory allocated to the HTTP client
Application Example¶
esp_err_t _http_event_handle(esp_http_client_event_t *evt) { switch(evt->event_id) { case HTTP_EVENT_ERROR: ESP_LOGI(TAG, "HTTP_EVENT_ERROR"); break; case HTTP_EVENT_ON_CONNECTED: ESP_LOGI(TAG, "HTTP_EVENT_ON_CONNECTED"); break; case HTTP_EVENT_HEADER_SENT: ESP_LOGI(TAG, "HTTP_EVENT_HEADER_SENT"); break; case HTTP_EVENT_ON_HEADER: ESP_LOGI(TAG, "HTTP_EVENT_ON_HEADER"); printf("%.*s", evt->data_len, (char*)evt->data); break; case HTTP_EVENT_ON_DATA: ESP_LOGI(TAG, "HTTP_EVENT_ON_DATA, len=%d", evt->data_len); if (!esp_http_client_is_chunked_response(evt->client)) { printf("%.*s", evt->data_len, (char*)evt->data); } break; case HTTP_EVENT_ON_FINISH: ESP_LOGI(TAG, "HTTP_EVENT_ON_FINISH"); break; case HTTP_EVENT_DISCONNECTED: ESP_LOGI(TAG, "HTTP_EVENT_DISCONNECTED"); break; } return ESP_OK; } esp_http_client_config_t config = { .url = "http://httpbin.org/redirect/2", .event_handler = _http_event_handle, }; esp_http_client_handle_t client = esp_http_client_init(&config); esp_err_t err = esp_http_client_perform(client); if (err == ESP_OK) { ESP_LOGI(TAG, "Status = %d, content_length = %d", esp_http_client_get_status_code(client), esp_http_client_get_content_length(client)); } esp_http_client_cleanup(client);
Persistent Connections¶
Persistent connections means that the HTTP client can re-use the same connection for several transfers. If the server does not request to close the connection with the Connection: close
header, the new transfer with sample ip address, port, and protocol.
To allow the HTTP client to take full advantage of persistent connections, you should do as many of your file transfers as possible using the same handle.
Persistent Connections example¶
esp_err_t err;
esp_http_client_config_t config = {
.url = "http://httpbin.org/get",
};
esp_http_client_handle_t client = esp_http_client_init(&config);
// first request
err = esp_http_client_perform(client);
// second request
esp_http_client_set_url(client, "http://httpbin.org/anything")
esp_http_client_set_method(client, HTTP_METHOD_DELETE);
esp_http_client_set_header(client, "HeaderKey", "HeaderValue");
err = esp_http_client_perform(client);
esp_http_client_cleanup(client);
HTTPS¶
The HTTP client supports SSL connections using mbedtls, with the url configuration starting with https
scheme (or transport_type = HTTP_TRANSPORT_OVER_SSL
). HTTPS support can be configured via :ref:CONFIG_ENABLE_HTTPS (enabled by default)..
注解
By providing information using HTTPS, the library will use the SSL transport type to connect to the server. If you want to verify server, then need to provide additional certificate in PEM format, and provide to cert_pem
in esp_http_client_config_t
HTTPS example¶
static void https()
{
esp_http_client_config_t config = {
.url = "https://www.howsmyssl.com",
.cert_pem = howsmyssl_com_root_cert_pem_start,
};
esp_http_client_handle_t client = esp_http_client_init(&config);
esp_err_t err = esp_http_client_perform(client);
if (err == ESP_OK) {
ESP_LOGI(TAG, "Status = %d, content_length = %d",
esp_http_client_get_status_code(client),
esp_http_client_get_content_length(client));
}
esp_http_client_cleanup(client);
}
HTTP Stream¶
Some applications need to open the connection and control the reading of the data in an active manner. the HTTP client supports some functions to make this easier, of course, once you use these functions you should not use the esp_http_client_perform()
function with that handle, and esp_http_client_init()
alway to called first to get the handle. Perform that functions in the order below:
esp_http_client_init()
: to create and handleesp_http_client_set_*
oresp_http_client_delete_*
: to modify the http connection information (optional)esp_http_client_open()
: Open the http connection withwrite_len
parameter,write_len=0
if we only need readesp_http_client_write()
: Upload data, max length equal towrite_len
ofesp_http_client_open()
function. We may not need to call it ifwrite_len=0
esp_http_client_fetch_headers()
: After sending the headers and write data (if any) to the server, this function will read the HTTP Server response headers. Calling this function will return thecontent-length
from the Server, and we can callesp_http_client_get_status_code()
for the HTTP status of the connection.esp_http_client_read()
: Now, we can read the HTTP stream by this function.esp_http_client_close()
: We should the connection after finishesp_http_client_cleanup()
: And release the resources
Perform HTTP request as Stream reader¶
Check the example function http_perform_as_stream_reader
at protocols/esp_http_client.
HTTP Authentication¶
The HTTP client supports both Basic and Digest Authentication. By providing usernames and passwords in url
or in the username
, password
of config entry. And with auth_type = HTTP_AUTH_TYPE_BASIC
, the HTTP client takes only 1 perform to pass the authentication process. If auth_type = HTTP_AUTH_TYPE_NONE
, but there are username
and password
in the configuration, the HTTP client takes 2 performs. The first time it connects to the server and receives the UNAUTHORIZED header. Based on this information, it will know which authentication method to choose, and perform it on the second.
Config authentication example with URI¶
esp_http_client_config_t config = {
.url = "http://user:[email protected]/basic-auth/user/passwd",
.auth_type = HTTP_AUTH_TYPE_BASIC,
};
Config authentication example with username, password entry¶
esp_http_client_config_t config = {
.url = "http://httpbin.org/basic-auth/user/passwd",
.username = "user",
.password = "passwd",
.auth_type = HTTP_AUTH_TYPE_BASIC,
};
HTTP Client example: protocols/esp_http_client.
API Reference¶
Header File¶
Functions¶
-
esp_http_client_handle_t
esp_http_client_init
(const esp_http_client_config_t *config)¶ Start a HTTP session This function must be the first function to call, and it returns a esp_http_client_handle_t that you must use as input to other functions in the interface. This call MUST have a corresponding call to esp_http_client_cleanup when the operation is complete.
- Return
esp_http_client_handle_t
- NULL if any errors
- Parameters
config
: The configurations, seehttp_client_config_t
-
esp_err_t
esp_http_client_perform
(esp_http_client_handle_t client)¶ Invoke this function after
esp_http_client_init
and all the options calls are made, and will perform the transfer as described in the options. It must be called with the same esp_http_client_handle_t as input as the esp_http_client_init call returned. esp_http_client_perform performs the entire request in either blocking or non-blocking manner. By default, the API performs request in a blocking manner and returns when done, or if it failed, and in non-blocking manner, it returns if EAGAIN/EWOULDBLOCK or EINPROGRESS is encountered, or if it failed. And in case of non-blocking request, the user may call this API multiple times unless request & response is complete or there is a failure. To enable non-blocking esp_http_client_perform(),is_async
member of esp_http_client_config_t must be set while making a call to esp_http_client_init() API. You can do any amount of calls to esp_http_client_perform while using the same esp_http_client_handle_t. The underlying connection may be kept open if the server allows it. If you intend to transfer more than one file, you are even encouraged to do so. esp_http_client will then attempt to re-use the same connection for the following transfers, thus making the operations faster, less CPU intense and using less network resources. Just note that you will have to useesp_http_client_set_**
between the invokes to set options for the following esp_http_client_perform.- Note
- You must never call this function simultaneously from two places using the same client handle. Let the function return first before invoking it another time. If you want parallel transfers, you must use several esp_http_client_handle_t. This function include
esp_http_client_open
->esp_http_client_write
->esp_http_client_fetch_headers
->esp_http_client_read
(and option)esp_http_client_close
. - Return
- ESP_OK on successful
- ESP_FAIL on error
- Parameters
client
: The esp_http_client handle
-
esp_err_t
esp_http_client_set_url
(esp_http_client_handle_t client, const char *url)¶ Set URL for client, when performing this behavior, the options in the URL will replace the old ones.
- Return
- ESP_OK
- ESP_FAIL
- Parameters
client
: The esp_http_client handleurl
: The url
-
esp_err_t
esp_http_client_set_post_field
(esp_http_client_handle_t client, const char *data, int len)¶ Set post data, this function must be called before
esp_http_client_perform
. Note: The data parameter passed to this function is a pointer and this function will not copy the data.- Return
- ESP_OK
- ESP_FAIL
- Parameters
client
: The esp_http_client handledata
: post data pointerlen
: post length
-
int
esp_http_client_get_post_field
(esp_http_client_handle_t client, char **data)¶ Get current post field information.
- Return
- Size of post data
- Parameters
client
: The clientdata
: Point to post data pointer
-
esp_err_t
esp_http_client_set_header
(esp_http_client_handle_t client, const char *key, const char *value)¶ Set http request header, this function must be called after esp_http_client_init and before any perform function.
- Return
- ESP_OK
- ESP_FAIL
- Parameters
client
: The esp_http_client handlekey
: The header keyvalue
: The header value
-
esp_err_t
esp_http_client_get_header
(esp_http_client_handle_t client, const char *key, char **value)¶ Get http request header. The value parameter will be set to NULL if there is no header which is same as the key specified, otherwise the address of header value will be assigned to value parameter. This function must be called after
esp_http_client_init
.- Return
- ESP_OK
- ESP_FAIL
- Parameters
client
: The esp_http_client handlekey
: The header keyvalue
: The header value
-
esp_err_t
esp_http_client_get_username
(esp_http_client_handle_t client, char **value)¶ Get http request username. The address of username buffer will be assigned to value parameter. This function must be called after
esp_http_client_init
.- Return
- ESP_OK
- ESP_ERR_INVALID_ARG
- Parameters
client
: The esp_http_client handlevalue
: The username value
-
esp_err_t
esp_http_client_set_username
(esp_http_client_handle_t client, const char *username)¶ Set http request username. The value of username parameter will be assigned to username buffer. If the username parameter is NULL then username buffer will be freed.
- Return
- ESP_OK
- ESP_ERR_INVALID_ARG
- Parameters
client
: The esp_http_client handleusername
: The username value
-
esp_err_t
esp_http_client_get_password
(esp_http_client_handle_t client, char **value)¶ Get http request password. The address of password buffer will be assigned to value parameter. This function must be called after
esp_http_client_init
.- Return
- ESP_OK
- ESP_ERR_INVALID_ARG
- Parameters
client
: The esp_http_client handlevalue
: The password value
-
esp_err_t
esp_http_client_set_password
(esp_http_client_handle_t client, char *password)¶ Set http request password. The value of password parameter will be assigned to password buffer. If the password parameter is NULL then password buffer will be freed.
- Return
- ESP_OK
- ESP_ERR_INVALID_ARG
- Parameters
client
: The esp_http_client handlepassword
: The password value
-
esp_err_t
esp_http_client_set_authtype
(esp_http_client_handle_t client, esp_http_client_auth_type_t auth_type)¶ Set http request auth_type.
- Return
- ESP_OK
- ESP_ERR_INVALID_ARG
- Parameters
client
: The esp_http_client handleauth_type
: The esp_http_client auth type
-
esp_err_t
esp_http_client_set_method
(esp_http_client_handle_t client, esp_http_client_method_t method)¶ Set http request method.
- Return
- ESP_OK
- ESP_ERR_INVALID_ARG
- Parameters
client
: The esp_http_client handlemethod
: The method
-
esp_err_t
esp_http_client_delete_header
(esp_http_client_handle_t client, const char *key)¶ Delete http request header.
- Return
- ESP_OK
- ESP_FAIL
- Parameters
client
: The esp_http_client handlekey
: The key
-
esp_err_t
esp_http_client_open
(esp_http_client_handle_t client, int write_len)¶ This function will be open the connection, write all header strings and return.
- Return
- ESP_OK
- ESP_FAIL
- Parameters
client
: The esp_http_client handlewrite_len
: HTTP Content length need to write to the server
-
int
esp_http_client_write
(esp_http_client_handle_t client, const char *buffer, int len)¶ This function will write data to the HTTP connection previously opened by esp_http_client_open()
- Return
- (-1) if any errors
- Length of data written
- Parameters
client
: The esp_http_client handlebuffer
: The bufferlen
: This value must not be larger than the write_len parameter provided to esp_http_client_open()
-
int
esp_http_client_fetch_headers
(esp_http_client_handle_t client)¶ This function need to call after esp_http_client_open, it will read from http stream, process all receive headers.
- Return
- (0) if stream doesn’t contain content-length header, or chunked encoding (checked by
esp_http_client_is_chunked
response) - (-1: ESP_FAIL) if any errors
- Download data length defined by content-length header
- (0) if stream doesn’t contain content-length header, or chunked encoding (checked by
- Parameters
client
: The esp_http_client handle
-
bool
esp_http_client_is_chunked_response
(esp_http_client_handle_t client)¶ Check response data is chunked.
- Return
- true or false
- Parameters
client
: The esp_http_client handle
-
int
esp_http_client_read
(esp_http_client_handle_t client, char *buffer, int len)¶ Read data from http stream.
- Return
- (-1) if any errors
- Length of data was read
- Parameters
client
: The esp_http_client handlebuffer
: The bufferlen
: The length
-
int
esp_http_client_get_status_code
(esp_http_client_handle_t client)¶ Get http response status code, the valid value if this function invoke after
esp_http_client_perform
- Return
- Status code
- Parameters
client
: The esp_http_client handle
-
int
esp_http_client_get_content_length
(esp_http_client_handle_t client)¶ Get http response content length (from header Content-Length) the valid value if this function invoke after
esp_http_client_perform
- Return
- (-1) Chunked transfer
- Content-Length value as bytes
- Parameters
client
: The esp_http_client handle
-
esp_err_t
esp_http_client_close
(esp_http_client_handle_t client)¶ Close http connection, still kept all http request resources.
- Return
- ESP_OK
- ESP_FAIL
- Parameters
client
: The esp_http_client handle
-
esp_err_t
esp_http_client_cleanup
(esp_http_client_handle_t client)¶ This function must be the last function to call for an session. It is the opposite of the esp_http_client_init function and must be called with the same handle as input that a esp_http_client_init call returned. This might close all connections this handle has used and possibly has kept open until now. Don’t call this function if you intend to transfer more files, re-using handles is a key to good performance with esp_http_client.
- Return
- ESP_OK
- ESP_FAIL
- Parameters
client
: The esp_http_client handle
-
esp_http_client_transport_t
esp_http_client_get_transport_type
(esp_http_client_handle_t client)¶ Get transport type.
- Return
- HTTP_TRANSPORT_UNKNOWN
- HTTP_TRANSPORT_OVER_TCP
- HTTP_TRANSPORT_OVER_SSL
- Parameters
client
: The esp_http_client handle
-
esp_err_t
esp_http_client_set_redirection
(esp_http_client_handle_t client)¶ Set redirection URL. When received the 30x code from the server, the client stores the redirect URL provided by the server. This function will set the current URL to redirect to enable client to execute the redirection request.
- Return
- ESP_OK
- ESP_FAIL
- Parameters
client
: The esp_http_client handle
-
void
esp_http_client_add_auth
(esp_http_client_handle_t client)¶ On receiving HTTP Status code 401, this API can be invoked to add authorization information.
- Note
- There is a possibility of receiving body message with redirection status codes, thus make sure to flush off body data after calling this API.
- Parameters
client
: The esp_http_client handle
-
bool
esp_http_client_is_complete_data_received
(esp_http_client_handle_t client)¶ Checks if entire data in the response has been read without any error.
- Return
- true
- false
- Parameters
client
: The esp_http_client handle
Structures¶
-
struct
esp_http_client_event
¶ HTTP Client events data.
Public Members
-
esp_http_client_event_id_t
event_id
¶ event_id, to know the cause of the event
-
esp_http_client_handle_t
client
¶ esp_http_client_handle_t context
-
void *
data
¶ data of the event
-
int
data_len
¶ data length of data
-
void *
user_data
¶ user_data context, from esp_http_client_config_t user_data
-
char *
header_key
¶ For HTTP_EVENT_ON_HEADER event_id, it’s store current http header key
-
char *
header_value
¶ For HTTP_EVENT_ON_HEADER event_id, it’s store current http header value
-
esp_http_client_event_id_t
-
struct
esp_http_client_config_t
¶ HTTP configuration.
Public Members
-
const char *
url
¶ HTTP URL, the information on the URL is most important, it overrides the other fields below, if any
-
const char *
host
¶ Domain or IP as string
-
int
port
¶ Port to connect, default depend on esp_http_client_transport_t (80 or 443)
-
const char *
username
¶ Using for Http authentication
-
const char *
password
¶ Using for Http authentication
-
esp_http_client_auth_type_t
auth_type
¶ Http authentication type, see
esp_http_client_auth_type_t
-
const char *
path
¶ HTTP Path, if not set, default is
/
-
const char *
query
¶ HTTP query
-
const char *
cert_pem
¶ SSL server certification, PEM format as string, if the client requires to verify server
-
const char *
client_cert_pem
¶ SSL client certification, PEM format as string, if the server requires to verify client
-
const char *
client_key_pem
¶ SSL client key, PEM format as string, if the server requires to verify client
-
esp_http_client_method_t
method
¶ HTTP Method
-
int
timeout_ms
¶ Network timeout in milliseconds
-
bool
disable_auto_redirect
¶ Disable HTTP automatic redirects
-
int
max_redirection_count
¶ Max redirection number, using default value if zero
-
http_event_handle_cb
event_handler
¶ HTTP Event Handle
-
esp_http_client_transport_t
transport_type
¶ HTTP transport type, see
esp_http_client_transport_t
-
int
buffer_size
¶ HTTP receive buffer size
-
int
buffer_size_tx
¶ HTTP transmit buffer size
-
void *
user_data
¶ HTTP user_data context
-
bool
is_async
¶ Set asynchronous mode, only supported with HTTPS for now
-
bool
use_global_ca_store
¶ Use a global ca_store for all the connections in which this bool is set.
-
bool
skip_cert_common_name_check
¶ Skip any validation of server certificate CN field
-
const char *
Macros¶
-
DEFAULT_HTTP_BUF_SIZE
¶
-
ESP_ERR_HTTP_BASE
¶ Starting number of HTTP error codes
-
ESP_ERR_HTTP_MAX_REDIRECT
¶ The error exceeds the number of HTTP redirects
-
ESP_ERR_HTTP_CONNECT
¶ Error open the HTTP connection
-
ESP_ERR_HTTP_WRITE_DATA
¶ Error write HTTP data
-
ESP_ERR_HTTP_FETCH_HEADER
¶ Error read HTTP header from server
-
ESP_ERR_HTTP_INVALID_TRANSPORT
¶ There are no transport support for the input scheme
-
ESP_ERR_HTTP_CONNECTING
¶ HTTP connection hasn’t been established yet
-
ESP_ERR_HTTP_EAGAIN
¶ Mapping of errno EAGAIN to esp_err_t
Type Definitions¶
-
typedef struct esp_http_client *
esp_http_client_handle_t
¶
-
typedef struct esp_http_client_event *
esp_http_client_event_handle_t
¶
-
typedef struct esp_http_client_event
esp_http_client_event_t
¶ HTTP Client events data.
-
typedef esp_err_t (*
http_event_handle_cb
)(esp_http_client_event_t *evt)¶
Enumerations¶
-
enum
esp_http_client_event_id_t
¶ HTTP Client events id.
Values:
-
HTTP_EVENT_ERROR
= 0¶ This event occurs when there are any errors during execution
-
HTTP_EVENT_ON_CONNECTED
¶ Once the HTTP has been connected to the server, no data exchange has been performed
-
HTTP_EVENT_HEADERS_SENT
¶ After sending all the headers to the server
-
HTTP_EVENT_HEADER_SENT
= HTTP_EVENT_HEADERS_SENT¶ This header has been kept for backward compatability and will be deprecated in future versions esp-idf
-
HTTP_EVENT_ON_HEADER
¶ Occurs when receiving each header sent from the server
-
HTTP_EVENT_ON_DATA
¶ Occurs when receiving data from the server, possibly multiple portions of the packet
-
HTTP_EVENT_ON_FINISH
¶ Occurs when finish a HTTP session
-
HTTP_EVENT_DISCONNECTED
¶ The connection has been disconnected
-
-
enum
esp_http_client_transport_t
¶ HTTP Client transport.
Values:
-
HTTP_TRANSPORT_UNKNOWN
= 0x0¶ Unknown
-
HTTP_TRANSPORT_OVER_TCP
¶ Transport over tcp
-
HTTP_TRANSPORT_OVER_SSL
¶ Transport over ssl
-
-
enum
esp_http_client_method_t
¶ HTTP method.
Values:
-
HTTP_METHOD_GET
= 0¶ HTTP GET Method
-
HTTP_METHOD_POST
¶ HTTP POST Method
-
HTTP_METHOD_PUT
¶ HTTP PUT Method
-
HTTP_METHOD_PATCH
¶ HTTP PATCH Method
-
HTTP_METHOD_DELETE
¶ HTTP DELETE Method
-
HTTP_METHOD_HEAD
¶ HTTP HEAD Method
-
HTTP_METHOD_NOTIFY
¶ HTTP NOTIFY Method
-
HTTP_METHOD_SUBSCRIBE
¶ HTTP SUBSCRIBE Method
-
HTTP_METHOD_UNSUBSCRIBE
¶ HTTP UNSUBSCRIBE Method
-
HTTP_METHOD_OPTIONS
¶ HTTP OPTIONS Method
-
HTTP_METHOD_MAX
¶
-