Trying to put together a string for HTTP GET

Projects Programming
1

Not doing something right

// Make a HTTP request:
char str0[] ="216.245.193.741/rick/push.asp";
char reada[4] = {digitalRead(1), digitalRead(2), digitalRead(3), digitalRead(4)};

char str5[] = {str0, "?ad1=", reada[0], "&ad2=", reada[1]};

//client.get(str5);

//test to see in monitor
Serial.println("String is ");
Serial.println(str5);

}

Giving me

String is
ɯµ

I must have data type problems. Hints are appreciated

2

There is no need to build a single string. Just send it in parts. The receiving device won't know the difference.

valA = digitalRead(pinA);
valB = digitalRead(pinB);
Serial.print("216.245.193.741/rick/push.asp");
Serial.print(valA);
Serial.print(' ');
Serial.print(valB);
// etc

I probably don't have the content right, but I think you will get the idea.

...R

3

char str5[] = {str0, "?ad1=", reada[0], "&ad2=", reada[1]} is an array of 4 chars. your output is 4 chars. everything is ok.

unless you need an array of 4 strings.
a constant string is const char* str0 ="216.245.193.741/rick/push.asp"
an array of constant strings is const char* str5[] = {str0, "?ad1=", "abcd", "&ad2=", "xyz"}

println can't print an array of strings. you can use sprintf to create formatted strings

char msg[100];
sprintf(msg,"%s?ad1=%d&ad2=%d", str0, digitalRead(1), digitalRead(2));
Serial.println(msg);
4 
 char reada[4] = {digitalRead(1), digitalRead(2), digitalRead(3), digitalRead(4)};

An array of non-printable characters is not going to prove useful.

5

Thanks, useful info for serial println. I am concerned that the function client.get() needs one big string thus the reason trying ways to construct it.

I need to end up with
"216.245.193.741/rick/push.asp?ad1=var1&ad2=var2&ad3=var3&ad4=var4";

I can't seem to pass any vars into the string.

R

6

I am concerned that the function client.get()

There is no client.get() function. There is a client.print() function that can print a GET request to a server. It makes some, but not much, difference if you use

client.print("GET ");
client.print(script);
client.print("?");
client.print("ad1=");
client.print(var1);
client.println(" HTTP/1.1");

vs.

char lotsOfStuff[80];
sprintf(lotsOfStuff, "GET %s?ad1=%d HTTP/1.1", script, var1);
client.println(lotsOfStuff);

Your GET request seems to incorrectly include the server name.

7

I'm not sure why you are sending the IP adress in the get request.

An HTTP get request is normally done by connecting to an IP address with a TCP connection and then sending

GET /foo/bar/myfile?param1=xxx&param2=yyy HTP/1.1
header1=something
header2=something else
<CR/LF blank line goes here>

8

I am on a YUN. This is from the examples / bridge / http client code

// Make a HTTP request:
client.get("http://www.arduino.cc/asciilogo.txt");

If I can hit the web address with my params the asp code will do the rest.

9

rheine:
I am on a YUN. This is from the examples / bridge / http client code

// Make a HTTP request:
client.get("http://www.arduino.cc/asciilogo.txt");

Ok - so the 'client' object does the job of pulling apart your URL.

What you want to do then is create an empty array of char[] that will be big enough to hold your URI, initialize element zero to '\0' (to turn it into a zero-lengh string), and then use the libc string functions to append the bits of your URI into that buffer.

char buf[100];
buf[0] = '\0';
char *p = buf;

strcpy(p, "http://216.245.193.741/rick/push.asp?ad1=");
while(*p) p++;
itoa(digitalRead(1), p, 10);
while(*p) p++;
strcpy(p, "&ad2=");
itoa(digitalRead(2), p, 10);

// buf[] now contains your string.
Serial.print("The URL is ");
Serial.println(buf);
10

Is my answer #2 hidden or what?

PaulMurrayCbr, why so complicated string concatenation?

11

rheine:
I am on a YUN. This is from the examples / bridge / http client code

Why on earth are you trying to formulate a GET string on the Arduino side of a Yun when you have all that Linux computing power on the same board?

...R

12

Juraj:
PaulMurrayCbr, why so complicated string concatenation?

It isn't complicated.

Robin2:
Why on earth are you trying to formulate a GET string on the Arduino side of a Yun when you have all that Linux computing power on the same board?

Very good point.

A small shell script that takes some parameters would be much easier to do.

13

PaulMurrayCbr:
It isn't complicated.

what is wrong with sprintf?

14

Juraj:
what is wrong with sprintf?

There is nothing wrong with sprintf. sprintf is a good solution for this problem.