HTTP AT Commands

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Introduction

Important

The default ESP32C2-4MB AT firmware supports HTTP functionality, while the ESP32C2-2MB AT firmware does not.. If you need ESP32C2-2MB to support HTTP commands, you can compile the ESP-AT project by following the steps in Compile ESP-AT Project Locally documentation. In the project configuration during the fifth step, make the following selections:

  • Enable Component config -> AT -> AT http command support

AT+HTTPCLIENT: Send HTTP Client Request

Set Command

Command:

AT+HTTPCLIENT=<opt>,<content-type>,<"url">,[<"host">],[<"path">],<transport_type>[,<"data">][,<"http_req_header">][,<"http_req_header">][...]

Response:

+HTTPCLIENT:<size>,<data>

OK

Parameters

  • <opt>: method of HTTP client request.

    • 1: HEAD

    • 2: GET

    • 3: POST

    • 4: PUT

    • 5: DELETE

  • <content-type>: data type of HTTP client request.

    • 0: application/x-www-form-urlencoded

    • 1: application/json

    • 2: multipart/form-data

    • 3: text/xml

  • <”url”>: HTTP URL. The parameter can override the <host> and <path> parameters if they are null.

  • <”host”>: domain name or IP address.

  • <”path”>: HTTP Path.

  • <transport_type>: HTTP Client transport type. Default: 1.

    • 1: HTTP_TRANSPORT_OVER_TCP

    • 2: HTTP_TRANSPORT_OVER_SSL

  • <”data”>: If <opt> is a POST request, this parameter holds the data you send to the HTTP server. If not, this parameter does not exist, which means there is no need to input a comma to indicate this parameter.

  • <http_req_header>: you can send more than one request header to the server.

Notes

  • If the length of the entire command containing the URL exceeds 256 bytes, please use the AT+HTTPURLCFG command to preset the URL first, and then set the <"url"> parameter of this command to "".

  • If the url parameter is not null, HTTP client will use it and ignore the host parameter and path parameter; If the url parameter is omited or null string, HTTP client will use host parameter and path parameter.

  • In some released firmware, HTTP client commands are not supported (see ESP-AT Firmware Differences), but you can enable it by ./build.py menuconfig > Component config > AT > AT http command support and build the project (see Compile ESP-AT Project Locally).

  • The command does not support redirection. After getting the status code 301 (permanent redirection) or 302 (temporary redirection) from the server, AT will not automatically redirect to the new URL address. You can use some tools to get the actual URL, and then access it using this command.

  • If the length of the entire command containing the <"data"> exceeds 256 bytes, please use the AT+HTTPCPOST command.

  • To set more HTTP request headers, use the AT+HTTPCHEAD command.

Example

// HEAD Request
AT+HTTPCLIENT=1,0,"http://httpbin.org/get","httpbin.org","/get",1

// GET Request
AT+HTTPCLIENT=2,0,"http://httpbin.org/get","httpbin.org","/get",1

// POST Request
AT+HTTPCLIENT=3,0,"http://httpbin.org/post","httpbin.org","/post",1,"field1=value1&field2=value2"

AT+HTTPGETSIZE: Get HTTP Resource Size

Set Command

Command:

AT+HTTPGETSIZE=<"url">[,<tx size>][,<rx size>][,<timeout>]

Response:

+HTTPGETSIZE:<size>

OK

Parameters

  • <”url”>: HTTP URL. It is a string parameter and should be enclosed with quotes.

  • <tx size>: HTTP send buffer size. Unit: byte. Default: 2048. Range: [0,10240].

  • <rx size>: HTTP receive buffer size. Unit: byte. Default: 2048. Range: [0,10240].

  • <timeout>: Network timeout. Unit: millisecond. Default: 5000. Range: [0,180000].

  • <size>: HTTP resource size.

Note

  • If the length of the entire command containing the URL exceeds 256 bytes, please use the AT+HTTPURLCFG command to preset the URL first, and then set the <"url"> parameter of this command to "".

  • To set HTTP request headers, use the AT+HTTPCHEAD command to set them.

Example

AT+HTTPGETSIZE="http://www.baidu.com/img/bdlogo.gif"

AT+HTTPCGET: Get HTTP Resource

Set Command

Command:

AT+HTTPCGET=<"url">[,<tx size>][,<rx size>][,<timeout>]

Response:

+HTTPCGET:<size>,<data>
OK

Parameters

  • <”url”>: HTTP URL. It is a string parameter and should be enclosed with quotes.

  • <tx size>: HTTP send buffer size. Unit: byte. Default: 2048. Range: [0,10240].

  • <rx size>: HTTP receive buffer size. Unit: byte. Default: 2048. Range: [0,10240].

  • <timeout>: Network timeout. Unit: millisecond. Default: 5000. Range: [0,180000].

Note

  • If the length of the entire command containing the URL exceeds 256 bytes, please use the AT+HTTPURLCFG command to preset the URL first, and then set the <"url"> parameter of this command to "".

  • To set HTTP request headers, use the AT+HTTPCHEAD command to set them.

AT+HTTPCPOST: Post HTTP data of specified length

Set Command

Command:

AT+HTTPCPOST=<"url">,<length>[,<http_req_header_cnt>][,<http_req_header>..<http_req_header>]

Response:

OK

>

The symbol > indicates that AT is ready for receiving serial data, and you can enter the data now. When the requirement of message length determined by the parameter <length> is met, the transmission starts.

If the transmission is successful, AT returns:

SEND OK

Otherwise, it returns:

SEND FAIL

Parameters

  • <”url”>: HTTP URL. It is a string parameter and should be enclosed with quotes.

  • <length>: HTTP data length to POST. The maximum length is equal to the system allocable heap size.

  • <http_req_header_cnt>: the number of <http_req_header> parameters.

  • [<http_req_header>]: HTTP request header. You can send more than one request header to the server.

Note

  • If the length of the entire command containing the URL exceeds 256 bytes, please use the AT+HTTPURLCFG command to preset the URL first, and then set the <"url"> parameter of this command to "".

  • the default type of content-type is application/x-www-form-urlencoded for this command.

  • To set HTTP request headers, use the AT+HTTPCHEAD command to set them.

AT+HTTPCPUT: Put HTTP data of specified length

Set Command

Command:

AT+HTTPCPUT=<"url">,<length>[,<http_req_header_cnt>][,<http_req_header>..<http_req_header>]

Response:

OK

>

The symbol > indicates that AT is ready for receiving serial data, and you can enter the data now. When the requirement of message length determined by the parameter <length> is met, the transmission starts.

If the transmission is successful, AT returns:

SEND OK

Otherwise, it returns:

SEND FAIL

Parameters

  • <”url”>: HTTP URL. It is a string parameter and should be enclosed with quotes.

  • <length>: HTTP data length to PUT. The maximum length is equal to the system allocable heap size.

  • <http_req_header_cnt>: the number of <http_req_header> parameters.

  • [<http_req_header>]: HTTP request header. You can send more than one request header to the server.

Note

  • If the length of the entire command containing the URL exceeds 256 bytes, please use the AT+HTTPURLCFG command to preset the URL first, and then set the <"url"> parameter of this command to "".

  • To set HTTP request headers, use the AT+HTTPCHEAD command to set them.

AT+HTTPURLCFG: Set/Get long HTTP URL

Query Command

Command:

AT+HTTPURLCFG?

Response:

[+HTTPURLCFG:<url length>,<data>]
OK

Set Command

Command:

AT+HTTPURLCFG=<url length>

Response:

OK

>

This response indicates that AT is ready for receiving serial data. You should enter the URL now, and when the URL length reaches the <url length> value, the system returns:

SET OK

Parameters

  • <url length>: HTTP URL length. Unit: byte.

    • 0: clean the HTTP URL configuration.

    • [8,8192]: set the HTTP URL configuration.

  • <data>: HTTP URL data.

AT+HTTPCHEAD: Set/Query HTTP Request Headers

Query Command

Command:

AT+HTTPCHEAD?

Response:

+HTTPCHEAD:<index>,<"req_header">

OK

Set Command

Command:

AT+HTTPCHEAD=<req_header_len>

Response:

OK

>

The > symbol indicates that AT is ready to receive AT command data. At this point, you can enter the HTTP request header (in the format of key: value). When the data length reaches the value of parameter <req_header_len>, AT returns:

OK

Parameters

  • <index>: Index value of HTTP request header.

  • <”req_header”>: HTTP request header.

  • <req_header_len>: HTTP request header length. Unit: byte.

    • 0: Clear all set HTTP request headers.

    • Other values: Set a new HTTP request header.

Note

  • This command can only set one HTTP request header at a time, but it can be set multiple times to support multiple different HTTP request headers.

  • The HTTP request headers configured by this command are global. Once set, all HTTP commands will carry these request headers.

  • If the key in the HTTP request header set by this command is the same as that of other HTTP commands, the HTTP request header set by this command will be used.

Example

// Set the request header
AT+HTTPCHEAD=18

// After receiving the ">" symbol, enter the Range request header below to download only the first 256 bytes of the resource
Range: bytes=0-255

// Download HTTP resource
AT+HTTPCGET="https://docs.espressif.com/projects/esp-at/en/latest/esp32c2/index.html"

HTTP AT Error Codes

  • HTTP Client:

    HTTP Client Error Code

    Description

    0x7000

    Failed to Establish Connection

    0x7190

    Bad Request

    0x7191

    Unauthorized

    0x7192

    Payment Required

    0x7193

    Forbidden

    0x7194

    Not Found

    0x7195

    Method Not Allowed

    0x7196

    Not Acceptable

    0x7197

    Proxy Authentication Required

    0x7198

    Request Timeout

    0x7199

    Conflict

    0x719a

    Gone

    0x719b

    Length Required

    0x719c

    Precondition Failed

    0x719d

    Request Entity Too Large

    0x719e

    Request-URI Too Long

    0x719f

    Unsupported Media Type

    0x71a0

    Requested Range Not Satisfiable

    0x71a1

    Expectation Failed

  • HTTP Server:

    HTTP Server Error Code

    Description

    0x71f4

    Internal Server Error

    0x71f5

    Not Implemented

    0x71f6

    Bad Gateway

    0x71f7

    Service Unavailable

    0x71f8

    Gateway Timeout

    0x71f9

    HTTP Version Not Supported

  • HTTP AT:

    • The error code of command AT+HTTPCLIENT will be 0x7000+Standard HTTP Error Code (For more details about Standard HTTP/1.1 Error Code, see RFC 2616).

    • For example, if AT gets the HTTP error 404 when calling command AT+HTTPCLIENT, it will respond with error code of 0x7194 (hex(0x7000+404)=0x7194).

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