{"id":2268,"date":"2020-12-05T11:58:16","date_gmt":"2020-12-05T10:58:16","guid":{"rendered":"https:\/\/www.pschatzmann.ch\/home\/?p=2268"},"modified":"2021-12-14T15:20:58","modified_gmt":"2021-12-14T14:20:58","slug":"wificlient-and-http","status":"publish","type":"post","link":"https:\/\/www.pschatzmann.ch\/home\/2020\/12\/05\/wificlient-and-http\/","title":{"rendered":"Simple HTTP Requests on Arduino Microcontrollers"},"content":{"rendered":"

For one of my current projects I had a closer look into the HTTP Protocol<\/strong>. Usually you might use a separate library<\/strong> for doing http calls from Arduino (e.g. with an ESP32) but if you are low on memory, you might get away without this by just using the WiFiClient<\/strong>:<\/p>\n

Setting up a WiFi connection<\/h3>\n

On an ESP32 you would e.g. do the following: First you need to connect to WiFI and then you can connect to the port 80 of your destination with the WiFiClient class:<\/p>\n

#include <WiFi.h>\n#include <WiFiClient.h>\n\nWiFi.begin(\"network name\", \"pwd\");\nwhile (WiFi.status() != WL_CONNECTED) {        \n  delay(500);\n   Serial.print(\".\");\n}\n\nWiFiClient client;\nconst char* host = \"www.pschatzmann.ch\";\nint port = 80;\n\nwhile (!client.connect(host, port)) {\n  delay(500);\n  Serial.print(\".\");\n}\n<\/code><\/pre>\n
HTTP Versions<\/h2>\n
During the years http<\/strong> made quite some evolutions<\/strong> each increasing the complexity<\/strong>.
\nFor the embedded devices the HTTP\/1.0<\/strong> is still your friend because it is simple<\/strong>!<\/p>\n
HTTP\/1.0<\/h3>\n
In order to make a http request you can just enter the following line, followed by an empty line. The official line endings are CR LF!<\/p>\n
\/\/ Make a HTTP request:\nclient.print(\"GET \/home\/ HTTP\/1.0\\r\\n\");\n\/\/ empty line -> end of header\nclient.print(\"\\r\\n\");\n<\/code><\/pre>\n
Though officially the lines should end with CR LF – usually a simple linefeed is also working and therefore you find that many other examples just use a simple client.println(“GET http::\/\/www.pschatzmann.ch\/home\/ HTTP\/1.0”)!<\/p>\n
After doing this request you can read the answer back. It consists of a the header information, followed by a empty line, followed by the data:<\/p>\n
if (client.connected()) {\n    \/\/ read header\n    while (client.available()) {\n        String line = client.readStringUntil('\\n');\n        if (line == \"\\r\") {\n            break;\n        }\n        Serial.writeln(line);\n    }    \n    \/\/ the remaining bytes is the data\n    while (client.available()) {\n      char c = client.read();\n      Serial.write(c);\n    }\n}\n<\/code><\/pre>\n
I also noticed that it’s not good if you use the connected() method while you are still in the process of receiving data!<\/p>\n
HTTP\/1.1<\/h3>\n
HTTP\/1.1 introduced the following functionality:<\/p>\n
    \n
  • persistent and pipelined connections, <\/li>\n
  • chunked transfers, <\/li>\n
  • compression\/decompression, <\/li>\n
  • content negotiations, <\/li>\n
  • virtual hosting<\/li>\n
  • cache support.<\/li>\n<\/ul>\n
    So if you decide to use HTTP\/1.1, you might need to add some additional logic or make sure that the additional functionality is not hurting you!<\/p>\n
    From my point of view the most relevant functionality is the ‘virtual hosting’ which means that you must<\/strong> now add a Host parameter<\/strong> to the request.<\/p>\n
    A valid request might look as follows:<\/p>\n
    client.print(\"GET \/home\/ HTTP\/1.1\\r\\n\");\nclient.print(\"Host: www.pschatzmann.ch\\r\\n\");\nclient.print(\"Connection: close\\r\\n\");\n\/\/ empty line -> end of header\nclient.print(\"\\r\\n\");\n<\/code><\/pre>\n
    Now you might receive chunked data<\/strong>, but if you don’t really want to deal with this, you can deactivate it by requesting the Accept-Encoding: identity__!<\/p>\n
    HTTPS<\/h2>\n
    It is almost as easy to connect to Https: You just need to replace the WiFiClient with WiFiClientSecure<\/strong> and connect to the 443 port<\/strong>!<\/p>\n
    #include <WiFiClientSecure.h>\n\nWiFiClientSecure client;\n\nconst char* host = \"www.pschatzmann.ch\";\nint port = 443;\nwhile (!client.connect(host, port)) {\n   delay(500);\n   Serial.print(\".\");\n}\n<\/code><\/pre>\n
    Conclusion<\/h2>\n
    It is very easy to implement some web requests using HTTP 1.0 (and if you are careful with HTTP 1.1 as well)<\/p>\n
    The good thing is, that for HTTP\/1.0<\/strong>  you can add the host parameter<\/strong> as well which might be relevant if you deal with a server that hosts multiple sites at the same address.<\/p>\n
    All later standards (HTTP\/2 HTTP\/3) however are too complex for the described approach and you will definitely need a separate library that deals with the additional complexity – if you really need to use this!<\/p>\n","protected":false},"excerpt":{"rendered":"
    For one of my current projects I had a closer look into the HTTP Protocol. Usually you might use a separate library for doing http calls from Arduino (e.g. with an ESP32) but if you are low on memory, you might get away without this by just using the WiFiClient: […]<\/p>\n","protected":false},"author":1,"featured_media":2289,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_crdt_document":"","_import_markdown_pro_load_document_selector":0,"_import_markdown_pro_submit_text_textarea":"","_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"footnotes":""},"categories":[20],"tags":[30],"class_list":["post-2268","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-arduino","tag-back-to-basics"],"yoast_head":"\nSimple HTTP Requests on Arduino Microcontrollers - Phil Schatzmann<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.pschatzmann.ch\/home\/2020\/12\/05\/wificlient-and-http\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Simple HTTP Requests on Arduino Microcontrollers - Phil Schatzmann\" \/>\n<meta property=\"og:description\" content=\"For one of my current projects I had a closer look into the HTTP Protocol. Usually you might use a separate library for doing http calls from Arduino (e.g. with an ESP32) but if you are low on memory, you might get away without this by just using the WiFiClient: […]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.pschatzmann.ch\/home\/2020\/12\/05\/wificlient-and-http\/\" \/>\n<meta property=\"og:site_name\" content=\"Phil Schatzmann\" \/>\n<meta property=\"article:published_time\" content=\"2020-12-05T10:58:16+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2021-12-14T14:20:58+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.pschatzmann.ch\/wp-content\/uploads\/2020\/12\/http.jpeg\" \/>\n\t<meta property=\"og:image:width\" content=\"225\" \/>\n\t<meta property=\"og:image:height\" content=\"225\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/jpeg\" \/>\n<meta name=\"author\" content=\"pschatzmann\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"pschatzmann\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"3 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/2020\\\/12\\\/05\\\/wificlient-and-http\\\/#article\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/2020\\\/12\\\/05\\\/wificlient-and-http\\\/\"},\"author\":{\"name\":\"pschatzmann\",\"@id\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/#\\\/schema\\\/person\\\/73a53638a4e34e8373405fd737dac9b1\"},\"headline\":\"Simple HTTP Requests on Arduino Microcontrollers\",\"datePublished\":\"2020-12-05T10:58:16+00:00\",\"dateModified\":\"2021-12-14T14:20:58+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/2020\\\/12\\\/05\\\/wificlient-and-http\\\/\"},\"wordCount\":455,\"commentCount\":0,\"publisher\":{\"@id\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/#\\\/schema\\\/person\\\/73a53638a4e34e8373405fd737dac9b1\"},\"image\":{\"@id\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/2020\\\/12\\\/05\\\/wificlient-and-http\\\/#primaryimage\"},\"thumbnailUrl\":\"https:\\\/\\\/www.pschatzmann.ch\\\/wp-content\\\/uploads\\\/2020\\\/12\\\/http.jpeg\",\"keywords\":[\"Back to Basics\"],\"articleSection\":[\"Arduino\"],\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"CommentAction\",\"name\":\"Comment\",\"target\":[\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/2020\\\/12\\\/05\\\/wificlient-and-http\\\/#respond\"]}]},{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/2020\\\/12\\\/05\\\/wificlient-and-http\\\/\",\"url\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/2020\\\/12\\\/05\\\/wificlient-and-http\\\/\",\"name\":\"Simple HTTP Requests on Arduino Microcontrollers - Phil Schatzmann\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/2020\\\/12\\\/05\\\/wificlient-and-http\\\/#primaryimage\"},\"image\":{\"@id\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/2020\\\/12\\\/05\\\/wificlient-and-http\\\/#primaryimage\"},\"thumbnailUrl\":\"https:\\\/\\\/www.pschatzmann.ch\\\/wp-content\\\/uploads\\\/2020\\\/12\\\/http.jpeg\",\"datePublished\":\"2020-12-05T10:58:16+00:00\",\"dateModified\":\"2021-12-14T14:20:58+00:00\",\"breadcrumb\":{\"@id\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/2020\\\/12\\\/05\\\/wificlient-and-http\\\/#breadcrumb\"},\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/2020\\\/12\\\/05\\\/wificlient-and-http\\\/\"]}]},{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/2020\\\/12\\\/05\\\/wificlient-and-http\\\/#primaryimage\",\"url\":\"https:\\\/\\\/www.pschatzmann.ch\\\/wp-content\\\/uploads\\\/2020\\\/12\\\/http.jpeg\",\"contentUrl\":\"https:\\\/\\\/www.pschatzmann.ch\\\/wp-content\\\/uploads\\\/2020\\\/12\\\/http.jpeg\",\"width\":225,\"height\":225},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/2020\\\/12\\\/05\\\/wificlient-and-http\\\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Simple HTTP Requests on Arduino Microcontrollers\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/#website\",\"url\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/\",\"name\":\"Phil Schatzmann Consulting\",\"description\":\"\",\"publisher\":{\"@id\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/#\\\/schema\\\/person\\\/73a53638a4e34e8373405fd737dac9b1\"},\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/?s={search_term_string}\"},\"query-input\":{\"@type\":\"PropertyValueSpecification\",\"valueRequired\":true,\"valueName\":\"search_term_string\"}}],\"inLanguage\":\"en-US\"},{\"@type\":[\"Person\",\"Organization\"],\"@id\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/#\\\/schema\\\/person\\\/73a53638a4e34e8373405fd737dac9b1\",\"name\":\"pschatzmann\",\"image\":{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\\\/\\\/www.pschatzmann.ch\\\/wp-content\\\/uploads\\\/2022\\\/08\\\/pschatzmann.png\",\"url\":\"https:\\\/\\\/www.pschatzmann.ch\\\/wp-content\\\/uploads\\\/2022\\\/08\\\/pschatzmann.png\",\"contentUrl\":\"https:\\\/\\\/www.pschatzmann.ch\\\/wp-content\\\/uploads\\\/2022\\\/08\\\/pschatzmann.png\",\"width\":305,\"height\":305,\"caption\":\"pschatzmann\"},\"logo\":{\"@id\":\"https:\\\/\\\/www.pschatzmann.ch\\\/wp-content\\\/uploads\\\/2022\\\/08\\\/pschatzmann.png\"}}]}<\/script>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"Simple HTTP Requests on Arduino Microcontrollers - Phil Schatzmann","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/www.pschatzmann.ch\/home\/2020\/12\/05\/wificlient-and-http\/","og_locale":"en_US","og_type":"article","og_title":"Simple HTTP Requests on Arduino Microcontrollers - Phil Schatzmann","og_description":"For one of my current projects I had a closer look into the HTTP Protocol. Usually you might use a separate library for doing http calls from Arduino (e.g. with an ESP32) but if you are low on memory, you might get away without this by just using the WiFiClient: […]","og_url":"https:\/\/www.pschatzmann.ch\/home\/2020\/12\/05\/wificlient-and-http\/","og_site_name":"Phil Schatzmann","article_published_time":"2020-12-05T10:58:16+00:00","article_modified_time":"2021-12-14T14:20:58+00:00","og_image":[{"width":225,"height":225,"url":"https:\/\/www.pschatzmann.ch\/wp-content\/uploads\/2020\/12\/http.jpeg","type":"image\/jpeg"}],"author":"pschatzmann","twitter_card":"summary_large_image","twitter_misc":{"Written by":"pschatzmann","Est. reading time":"3 minutes"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"Article","@id":"https:\/\/www.pschatzmann.ch\/home\/2020\/12\/05\/wificlient-and-http\/#article","isPartOf":{"@id":"https:\/\/www.pschatzmann.ch\/home\/2020\/12\/05\/wificlient-and-http\/"},"author":{"name":"pschatzmann","@id":"https:\/\/www.pschatzmann.ch\/home\/#\/schema\/person\/73a53638a4e34e8373405fd737dac9b1"},"headline":"Simple HTTP Requests on Arduino Microcontrollers","datePublished":"2020-12-05T10:58:16+00:00","dateModified":"2021-12-14T14:20:58+00:00","mainEntityOfPage":{"@id":"https:\/\/www.pschatzmann.ch\/home\/2020\/12\/05\/wificlient-and-http\/"},"wordCount":455,"commentCount":0,"publisher":{"@id":"https:\/\/www.pschatzmann.ch\/home\/#\/schema\/person\/73a53638a4e34e8373405fd737dac9b1"},"image":{"@id":"https:\/\/www.pschatzmann.ch\/home\/2020\/12\/05\/wificlient-and-http\/#primaryimage"},"thumbnailUrl":"https:\/\/www.pschatzmann.ch\/wp-content\/uploads\/2020\/12\/http.jpeg","keywords":["Back to Basics"],"articleSection":["Arduino"],"inLanguage":"en-US","potentialAction":[{"@type":"CommentAction","name":"Comment","target":["https:\/\/www.pschatzmann.ch\/home\/2020\/12\/05\/wificlient-and-http\/#respond"]}]},{"@type":"WebPage","@id":"https:\/\/www.pschatzmann.ch\/home\/2020\/12\/05\/wificlient-and-http\/","url":"https:\/\/www.pschatzmann.ch\/home\/2020\/12\/05\/wificlient-and-http\/","name":"Simple HTTP Requests on Arduino Microcontrollers - Phil Schatzmann","isPartOf":{"@id":"https:\/\/www.pschatzmann.ch\/home\/#website"},"primaryImageOfPage":{"@id":"https:\/\/www.pschatzmann.ch\/home\/2020\/12\/05\/wificlient-and-http\/#primaryimage"},"image":{"@id":"https:\/\/www.pschatzmann.ch\/home\/2020\/12\/05\/wificlient-and-http\/#primaryimage"},"thumbnailUrl":"https:\/\/www.pschatzmann.ch\/wp-content\/uploads\/2020\/12\/http.jpeg","datePublished":"2020-12-05T10:58:16+00:00","dateModified":"2021-12-14T14:20:58+00:00","breadcrumb":{"@id":"https:\/\/www.pschatzmann.ch\/home\/2020\/12\/05\/wificlient-and-http\/#breadcrumb"},"inLanguage":"en-US","potentialAction":[{"@type":"ReadAction","target":["https:\/\/www.pschatzmann.ch\/home\/2020\/12\/05\/wificlient-and-http\/"]}]},{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/www.pschatzmann.ch\/home\/2020\/12\/05\/wificlient-and-http\/#primaryimage","url":"https:\/\/www.pschatzmann.ch\/wp-content\/uploads\/2020\/12\/http.jpeg","contentUrl":"https:\/\/www.pschatzmann.ch\/wp-content\/uploads\/2020\/12\/http.jpeg","width":225,"height":225},{"@type":"BreadcrumbList","@id":"https:\/\/www.pschatzmann.ch\/home\/2020\/12\/05\/wificlient-and-http\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/www.pschatzmann.ch\/home\/"},{"@type":"ListItem","position":2,"name":"Simple HTTP Requests on Arduino Microcontrollers"}]},{"@type":"WebSite","@id":"https:\/\/www.pschatzmann.ch\/home\/#website","url":"https:\/\/www.pschatzmann.ch\/home\/","name":"Phil Schatzmann Consulting","description":"","publisher":{"@id":"https:\/\/www.pschatzmann.ch\/home\/#\/schema\/person\/73a53638a4e34e8373405fd737dac9b1"},"potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/www.pschatzmann.ch\/home\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"en-US"},{"@type":["Person","Organization"],"@id":"https:\/\/www.pschatzmann.ch\/home\/#\/schema\/person\/73a53638a4e34e8373405fd737dac9b1","name":"pschatzmann","image":{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/www.pschatzmann.ch\/wp-content\/uploads\/2022\/08\/pschatzmann.png","url":"https:\/\/www.pschatzmann.ch\/wp-content\/uploads\/2022\/08\/pschatzmann.png","contentUrl":"https:\/\/www.pschatzmann.ch\/wp-content\/uploads\/2022\/08\/pschatzmann.png","width":305,"height":305,"caption":"pschatzmann"},"logo":{"@id":"https:\/\/www.pschatzmann.ch\/wp-content\/uploads\/2022\/08\/pschatzmann.png"}}]}},"post_mailing_queue_ids":[],"_links":{"self":[{"href":"https:\/\/www.pschatzmann.ch\/home\/wp-json\/wp\/v2\/posts\/2268","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.pschatzmann.ch\/home\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.pschatzmann.ch\/home\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.pschatzmann.ch\/home\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.pschatzmann.ch\/home\/wp-json\/wp\/v2\/comments?post=2268"}],"version-history":[{"count":30,"href":"https:\/\/www.pschatzmann.ch\/home\/wp-json\/wp\/v2\/posts\/2268\/revisions"}],"predecessor-version":[{"id":2299,"href":"https:\/\/www.pschatzmann.ch\/home\/wp-json\/wp\/v2\/posts\/2268\/revisions\/2299"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.pschatzmann.ch\/home\/wp-json\/wp\/v2\/media\/2289"}],"wp:attachment":[{"href":"https:\/\/www.pschatzmann.ch\/home\/wp-json\/wp\/v2\/media?parent=2268"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.pschatzmann.ch\/home\/wp-json\/wp\/v2\/categories?post=2268"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.pschatzmann.ch\/home\/wp-json\/wp\/v2\/tags?post=2268"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}