ESP8266-Arduino网络编程实例-简单HTTP数据请求（基于Node-Red）

简单HTTP数据请求

超文本传输协议 (HTTP) 用作客户端和服务器之间的请求-响应协议。本实例将演示如何通过ESP8266发起一个HTTP请求，向远程主机请求数据。

在开始本实例之前，首先准备一个可用的HTTP服务器，或一个可用的HTTP URL。在这里，通过Node-Red物联网编程环境创建一个数据请求节点。Node-Red安装步骤如下：

  • 下载并安装node.js
  • 在命令行中运行

npm -g install node-red

  • 在Node-Red安装完成后，在命令行中运行：

node-red

启动Node-Red服务器，Node-Red默认端口为1880

  • 接着，在浏览器打开Node-Red

http://localhost:1880

  • 最后创建运行节点，并创建一个时间请求流程：

在这里插入图片描述

在函数节点中，输入如下代码：

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// Create a Date object from the payload
var date = new Date();
// Change the payload to be a formatted Date string
msg.payload = date.toString();
// Return the message so it can be sent on

如果不太熟悉操作的，可以复制本实例的节点代码导入即可：

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[
    {
        "id": "60551d068a09952f",
        "type": "http in",
        "z": "65febd16d6c14bb0",
        "name": "date\_time\_request",
        "url": "/date\_time",
        "method": "get",
        "upload": false,
        "swaggerDoc": "",
        "x": 270,
        "y": 140,
        "wires": [
            [
                "764de1bfd43df11a"
            ]
        ]
    },
    {
        "id": "764de1bfd43df11a",
        "type": "function",
        "z": "65febd16d6c14bb0",
        "name": "",
        "func": "// Create a Date object from the payload\nvar date = new Date();\n// Change the payload to be a formatted Date string\nmsg.payload = date.toString();\n// Return the message so it can be sent on\nreturn msg;",
        "outputs": 1,
        "noerr": 0,
        "initialize": "",
        "finalize": "",
        "libs": [],
        "x": 450,
        "y": 140,
        "wires": [
            [
                "12b4b3fbbe4b272e",
                "bc6ef9d8bbc1208d"
            ]
        ]
    },
    {
        "id": "12b4b3fbbe4b272e",
        "type": "http response",
        "z": "65febd16d6c14bb0",
        "name": "http(200)",
        "statusCode": "",
        "headers": {},
        "x": 680,
        "y": 100,
        "wires": []
    },
    {
        "id": "bc6ef9d8bbc1208d",
        "type": "debug",
        "z": "65febd16d6c14bb0",
        "name": "msg.payload",
        "active": true,
        "tosidebar": true,
        "console": true,
        "tostatus": false,
        "complete": "payload",
        "targetType": "msg",
        "statusVal": "",
        "statusType": "auto",
        "x": 700,
        "y": 160,
        "wires": []
    }
]

最后，点击右上角的部署或Deploy按钮，完成流程部署。

  • ESP8266（客户端）向运行 Node-RED服务器提交 HTTP 请求；
  • Node-RED服务器向 ESP8266（客户端）返回响应；
  • 最后，响应包含有关请求的状态信息，也可能包含请求的内容。

ESP8266作为HTTP客户端，发起HTTP Get请求的代码如下：

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#include <ESP8266WiFi.h>
#include <ESP8266HTTPClient.h>
#include <WiFiClient.h>

const char\* ssid = "\*\*\*\*\*"; // WIFI名称
const char\* password = "\*\*\*\*\*"; // WIFI密码

// HTTP请求URL
String serverName = "http://192.168.0.164:1880/date\_time";

unsigned long lastTime = 0;
unsigned long timerDelay = 5000;

void setup() {
  Serial.begin(115200); 

  WiFi.begin(ssid, password);
  Serial.println("Connecting");
  while(WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("");
  Serial.print("Connected to WiFi network with IP Address: ");
  Serial.println(WiFi.localIP());
 
  Serial.println("Timer set to 5 seconds (timerDelay variable), it will take 5 seconds before publishing the first reading.");
}

void loop() {
  // 每5秒发起一次请求
  if ((millis() - lastTime) > timerDelay) {
    //Check WiFi connection status
    if(WiFi.status()== WL_CONNECTED){
      WiFiClient client;
      HTTPClient http;

      String serverPath = serverName + "?temperature=24.37";
      
      // 启动HTTP请求
      http.begin(client, serverPath.c\_str());
      
      // 查询HTTP请求的响应状态
      int httpResponseCode = http.GET();
      
      if (httpResponseCode>0) {
        Serial.print("HTTP Response code: ");
        Serial.println(httpResponseCode);
        String payload = http.getString();
        Serial.println(payload);
      }
      else {
        Serial.print("Error code: ");
        Serial.println(httpResponseCode);
      }
      // 释放HTTP请求
      http.end();
    }
    else {
      Serial.println("WiFi Disconnected");
    }
    lastTime = millis();
  }
}

示例代码如何运行？

1）导入依赖头文件

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#include <ESP8266WiFi.h>
#include <ESP8266HTTPClient.h>
#include <WiFiClient.h>

2）启动WiFi连接

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WiFi.begin(ssid, password);
Serial.println("Connecting");
while(WiFi.status() != WL_CONNECTED) {
  delay(500);
  Serial.print(".");
}

3）发起HTTP请求

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WiFiClient client;
      HTTPClient http;

      String serverPath = serverName + "?temperature=24.37";
      
      // 启动HTTP请求
      http.begin(client, serverPath.c\_str());

4）处理HTTP请求响应

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// 查询HTTP请求的响应状态
int httpResponseCode = http.GET();

if (httpResponseCode>0) {
  Serial.print("HTTP Response code: ");
  Serial.println(httpResponseCode);
  String payload = http.getString();
  Serial.println(payload);
}
else {
  Serial.print("Error code: ");
  Serial.println(httpResponseCode);
}

5）释放HTTP请求占用资源

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http.end();

运行结果如下：

在这里插入图片描述

文章来源: https://iotsmart.blog.csdn.net/article/details/127164824