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webarduinoesp32

ESP32 - unable to connect to Google Coud VM running Node-Red httpin node with post/get request

I have a Google Cloud Debian VM with Node Red installed. I created a flow that is refered as json on the httpin node. When I http://xx.xx.xx.xx:1880/json from chrome, Node Red at the VM responds with a test json string I typed there.

My intention is to post a json from ESP32 and get a response from Node Red. But I am just unable to even connect with the above URL from ESP32.

At the top of my sketch I have:

String URLWebServer          = "http://222.222.111.128";
int    PortWebServer         = 1880;
String uploadScript          = "/json";

Later in the sketch I have the web connection as below:

void postWebServer(){
  Serial.print("Connect to " + URLWebServer);
  if (webClient.connect(URLWebServer.c_str(), PortWebServer)){
    Serial.println(" -> OK");
...
...
...
  }else{
    Serial.println(" -> Fail");
  }

And no matter what I do I always get "-> Fail").

Assistance welcome.

The sketch is divided in several tabs with specific functions. This is the same sketch I use to connect with another online service and it used to work. Now I am developing my own service using nodered. When this function is called WiFi is already connected. Complete code of the function that does the web post:

void postWebServer(){
  Serial.print("Connect to " + URLWebServer); 
  if (webClient.connect(URLWebServer.c_str(), PortWebServer)){
    Serial.println(" -> OK");
    String startBoundary = "--";
    String postTail = startBoundary + boundary + "--" + newLine;

    String strBody;  // = newLine;
    strBody += startBoundary + boundary + newLine;
    strBody += "Content-Disposition: form-data; name=\"filename\"" + newLine + newLine;
    strBody += ftpFileName + newLine;
    
    strBody += startBoundary + boundary + newLine;
    strBody += "Content-Disposition: form-data; name=\"devid\"" + newLine + newLine;
    strBody += devid + newLine;

    strBody += startBoundary + boundary + newLine;
    strBody += "Content-Disposition: form-data; name=\"latitude\"" + newLine + newLine;
    strBody += "123" + newLine;    

    strBody += startBoundary + boundary + newLine;
    strBody += "Content-Disposition: form-data; name=\"longitude\"" + newLine + newLine;
    strBody += "345" + newLine;    

    strBody += startBoundary + boundary + newLine;
    strBody += "Content-Disposition: form-data; name=\"camera_id\"" + newLine + newLine;
    strBody += camera_id + newLine;

    strBody += startBoundary + boundary + newLine;
    strBody += "Content-Disposition: form-data; name=\"maxSpeed\"" + newLine + newLine;
    strBody += "40" + newLine;

    strBody += startBoundary + boundary + newLine;
    strBody += "Content-Disposition: form-data; name=\"radarSpeed\"" + newLine + newLine;
    strBody += "65" + newLine;    

    strBody += startBoundary + boundary + newLine;
    strBody += "Content-Disposition: form-data; name=\"plate\"" + newLine + newLine;
    strBody += plate + newLine;

    strBody += startBoundary + boundary + newLine;
    strBody += "Content-Disposition: form-data; name=\"type\"" + newLine + newLine;
    strBody += type + newLine;

    strBody += startBoundary + boundary + newLine;
    strBody += "Content-Disposition: form-data; name=\"make\"" + newLine + newLine;
    strBody += make + newLine;

    strBody += startBoundary + boundary + newLine;
    strBody += "Content-Disposition: form-data; name=\"model\"" + newLine + newLine;
    strBody += model + newLine;        

    strBody += startBoundary + boundary + newLine;
    strBody += "Content-Disposition: form-data; name=\"color\"" + newLine + newLine;
    strBody += color + newLine;
    strBody += postTail;  
    
    Serial.println("Connection to " + URLWebServer + " - OK"); 
    String header = "POST " + uploadScript + " HTTP/1.1" + newLine;    
    header += "Host: " + URLWebServer + newLine;      
    header += "Content-Type: multipart/form-data; boundary=" + boundary + newLine;    
    header += "Content-Length: " + String(strBody.length()) + newLine;
    header += newLine;

    webClient.print(header);
    pDBGln(header);                
    webClient.print(strBody);  
    pDBGln(strBody + newLine);
        
    Serial.println("Data sent to " + URLWebServer + "...");

  }else{
    Serial.println(" -> Fail");
  }  
}
Solution

  • Best guess since you haven't really provided enough context to your ESP32 code.

    But it looks like webClient is actually an ethernet/wifi client since you are building the HTTP request by hand in the function you have provided.

    You need to take the http:// off the start of the URLWebServer it should be a hostname/ip address not a URL, since you are passing the port as a separate argument.

    You will need to include the http:// in the HTTP Host header (along with the port number)

    https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Host