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Editorial Team
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Asked: 2026-05-13T13:03:46+00:00

I am writing an arduino library to post http request on web. I am

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I am writing an arduino library to post http request on web.

I am using the String class from http://arduino.cc/en/Tutorial/TextString

My code is behaving strangely when I am referring to my defined string objects after a function call.

Here actually I am trying to get the body of my GET request and removing the http headers from the http GET request’s response.

Following is the description:

Method Call: 

  String body;  
  if(pinger.Get(host,path,&body))
  {
    Serial.println("Modified String Outside :");
    Serial.println(body);
    Serial.println();
    Serial.println("Modified String Outside Address");
    Serial.println((int)&body);
  }

Output

Modified String Outside :
HTTP/1.1 200 OK
Server: Apache-Coyote/1.1
Content-Type: text/html
Content-Length: 113
Date: Wed, 13 Jan 2010 14:36:28 GMT

<html>
<head>
<title>Ashish Sharma
</title>
</head>
<body>
Wed Jan 13 20:06:28 IST 2010
</body>
</html>


Modified String Outside Address
2273

Method Description:

bool Pinger::Get(String host, String path, String *response) {
    bool connection = false;
    bool status = false;

    String post1 = "GET ";
    post1 = post1.append(path);
    post1 = post1.append(" HTTP/1.1");

    String host1 = "Host: ";
    host1 = host1.append(host);

    for (int i = 0; i < 10; i++) {
        if (client.connect()) {
            client.println(post1);
            client.println(host1);
            client.println();
            connection = true;
            break;
        }
    }

    int nlCnt = 0;
    while (connection) {
        if (client.available()) {
            int c = client.read();
            response->append((char) c);
            if (c == 0x000A && nlCnt == 0) {
                nlCnt++;
                if (response->contains("200")) {
                        status = true;
                        continue;
                    } else {
                        client.stop();
                        client.flush();
                        break;
                    }   
            }
        }
        if (!client.connected()) {
            client.stop();
            connection = false;
        }
    }           
    response = &response->substring(response->indexOf("\n\r\n"),response->length());    
    Serial.println("Modified String: ");
    Serial.println(*response);  

    Serial.println();
    Serial.print("Modified String Address: ");
    Serial.println((int)&response);
    return status;
}

Output:

Modified String: 
Ø
<html>
<head>
<title>Ashish Sharma
</title>
</head>
<body>
Wed Jan 13 20:06:28 IST 2010
</body>
</html>

Modified String Address: 2259

As can be seen from the example the string reference object is giving me the correct string inside the Get method but the reference of the string contents change when the Get method returns.

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1 Answer

  1. Editorial Team

    If I understood correctly your code, you probably would want to do something like this:

    *response = response->substring(response->indexOf("\n\r\n"),response->length());

    instead of

    response = &response->substring(response->indexOf("\n\r\n"),response->length());

    Also there’s probably no need to pass in a pointer ( reference would probably make the code look much nicer ).

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