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

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");
  }  
}

CodePudding user response：

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