Controllino MAXI对接Firebase Realtime Database REST API PUT请求报404问题

基础信息 #

• 硬件平台：Controllino MAXI，本质为搭载以太网芯片的Arduino Mega 2560，参考产品介绍Controllino MAXI
• 开发目标：通过Firebase Realtime Database提供的REST API，实现开发板向数据库传输数据的功能
• 当前故障现象：所有类型的HTTP请求均无法正常生效，现阶段优先聚焦PUT请求的链路排查

正常验证链路 #

使用在线测试工具reqbin验证PUT请求可正常完成写入，对应原始请求报文：

PUT /.json HTTP/1.1
Host: *rtdb-name*.firebaseio.com
Content-Type: application/json
Content-Length: 26

{"message":"hello world!"}

请求返回的正常响应内容：

{
    "message": "hello world!"
}

对应响应头信息：

Server: nginx
Date: Wed, 03 Feb 2021 17:02:55 GMT
Content-Type: application/json; charset=utf-8
Content-Length: 26
Connection: keep-alive
Access-Control-Allow-Origin: *
Cache-Control: no-cache
Strict-Transport-Security: max-age=31556926; includeSubDomains; preload

请求可正常将数据写入Realtime Database根节点，写入效果参考截图：

开发板端异常表现 #

在开发板上调用Arduino Ethernet库，编写逻辑完全一致的请求代码，核心片段如下：

char server[] = "rtdb-name.firebaseio.com"
if (client.connect(server,80)){
    String data = "{\"message\":\"hello world!\"}";
    Serial.println("connected");
    client.println("PUT /.json HTTP/1.1");
    client.println("Host: *rtdb-name*.firebaseio.com");
    client.println("User-Agent: Arduino/1.0");
    client.println("Cache-Control:  no-cache, no-store, must-revalidate");
    client.println("Pragma: no-cache");
    client.println("Expires: 0");
    client.println("Content-Type: application/json");
    client.println("Connection: close");
    client.print("Content-Length: ");
    client.println(data.length());
    client.println();
    client.println(data);

    while(client.connected()) {
      while (client.available()) {
        char c = client.read();
        Serial.print(c);
      }
    }
   client.stop();     
   Serial.println("disconnected");
}else{
    Serial.println("Failed to connect to server");
}

实际收到的返回为404错误，报文内容：

HTTP/1.1 404 Not Found
Content-Type: text/html; charset=UTF-8
Referrer-Policy: no-referrer
Content-Length: 1566
Date: Wed, 03 Feb 2021 17:06:07 GMT
Connection: close

初步推测方向 #

目前暂未定位到问题根因，初步判断可能是Firebase Realtime Database站点采用HTTPS协议强制跳转，而基于Mega架构的开发板原生仅支持HTTP通信，需要对应的技术指导与解决方案。

内容的提问来源于stack exchange，提问作者SRR