How to use a value send from my web page to arduino?

Hi everybody.
I found a sketch on the web to control a camera and send a hposition and a vposition to the arduino.
But the sketch was incomplete and I dont know how to use this datas…
When I send 100 and 200, the request is: http://192.168.0.177/?vpos=100&hpos=200
But how to use this values?
Thank you for your help.
Here is my code:

#include <SPI.h>
#include <Ethernet.h>

#include <Servo.h>
Servo myservo; // create servo object to control a servo

byte mac = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED }; //physical mac address
byte ip = { 192, 168, 0, 177 }; // ip in lan
byte gateway = { 192, 168, 0, 1 }; // internet access via router
byte subnet = { 255, 255, 255, 0 }; //subnet mask
EthernetServer server(80); //server port

String readString;

//////////////////////

void setup(){

pinMode(12, OUTPUT); //pin selected to control
//start Ethernet
Ethernet.begin(mac, ip, gateway, subnet);
server.begin();

myservo.write(90); //set initial servo position if desired
myservo.attach(7); //the pin for the servo co
//enable serial data print
Serial.begin(9600);
Serial.println(“server LED test 1.0”); // so I can keep track of what is loaded
}

void loop(){
// Create a client connection
EthernetClient client = server.available();
if (client) {
while (client.connected()) {
if (client.available()) {
char c = client.read();

//read char by char HTTP request
if (readString.length() < 100) {

//store characters to string
readString += c;
//Serial.print(c);
}

//if HTTP request has ended
if (c == ‘\n’) {

///////////////
Serial.println(readString); //print to serial monitor for debuging

client.println(“HTTP/1.1 200 OK”); //send new page
client.println(“Content-Type: text/html”);
client.println();

client.println("");
client.println("");
client.println(“Arduino GET test page”);
client.println("");
client.println("");

client.println(“

Zoomkat’s simple Arduino button

”);

client.print("");
client.println("");
client.println("");
client.println("");
client.println(“Initial Vertical Position:
“);
client.println(“Initial Horizontal Position:
“);
client.println(””);
client.println(””);

client.println("");
client.println("");
client.println("");

delay(1);
//stopping client
client.stop();
int a;int b;
///////////////////// control arduino pin
if(readString.indexOf(“vpos”) >0)//checks for on
{
Serial.println(“I want to know the vpos value”);
a=‘vpos’;
Serial.println(a);//doesn’ work…

}
if(readString.indexOf(“hpos”) >0)//checks for off
{

Serial.println(“I want to know the hpos value”);
b=‘vpos’;
Serial.println(b);
}
//clearing string for next read
readString="";

}
}
}
}
}

you need to parse the readString a bit more.

int a_start = readString.indexOf("vpos=") + 5; // find the begin of your number. Need to add 5 as "vpos=" has a length of 5
int a_end = readString.indexOf("&", a_start); // find the end of your number, start to search at the beginning of your number
if (a_end<0) a_end = readString.length(); // if no delimiter is found, the number ends at the end of the readString

if (a_start>=0) char[] a_val = readString.substr(a_start, a_end).c_str; // Extract the number

int a = atoi(a_val); // convert it to int

and then the same for hpos / b.

char[] a_val = readString.substr(a_start, a_end);

Is this valid C ? It looks a lot like Java to me.

C no, but C++,isn't it?.

Well, apart from anything else the String library does not have a method named substr
How big is the a_val array and will that line of code put the substring into the array ?

C no, but C++,isn't it?.

No. C# and Java put the after the type. C and C++ put the after the variable name.