Textual Display Over Network

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

#define MaxHeaderLength 47    //maximum length of http header required

#include <Wire.h>
#include <Adafruit_MCP23017.h>
#include <Adafruit_RGBLCDShield.h>
Adafruit_RGBLCDShield lcd = Adafruit_RGBLCDShield();

byte mac[] = {
  0x90, 0xA2, 0xDA, 0x0D, 0x35, 0x70 }; //physical mac address
byte ip[] = {
  10,0,0, 26 };
byte gateway[] = {
  10,0,0, 1 };
byte subnet[] = {
  255, 255, 255, 0 };
EthernetServer server(76); //arduino server port

String HttpHeader = String(MaxHeaderLength);
String displayText1 = "1";
String displayText2 = "2";

void setup(){
  //enable serial monitor
  Serial.begin(9600);
  //start Ethernet
  Ethernet.begin(mac, ip, gateway, subnet);

  //initialize variable
  HttpHeader="";
  displayText1="";
  displayText2="";

  lcd.begin(16,2);
  lcd.print("SystemOnline");
  Serial.print("System Online");
}

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

        char c = client.read();
        //read MaxHeaderLength number of characters in the HTTP header
        //discard the rest until \n
        if (HttpHeader.length() < MaxHeaderLength){
          //store characters to string
         HttpHeader = HttpHeader + c;
         HttpHeader.replace("HTTP/1.1"," ");
         HttpHeader.replace("+", " ");
          if (HttpHeader.startsWith("GET /?text")){
            displayText1 = HttpHeader.substring(11,27);
            displayText2 = HttpHeader.substring(28,44);
          }
        }
        lcd.clear();
        lcd.print(displayText1);
        lcd.setCursor(1,1);
        lcd.print(displayText2);

        //if HTTP request has ended
        if (c == '\n') {
          // show the string on the monitor
          Serial.println(HttpHeader);
          // start of web page
          client.println("HTTP/1.1 200 OK");
          client.println("Content-Type: text/html");
          client.println("<html><head></head><body>");
          client.println();
          client.print("<form method=get>");
          client.print("Enter in a 16 character string");
          client.print("<input type='text' name=text><br>");
          client.print("<input type=submit value=submit></form>");
          client.print("</body></html>");

          //clearing string for next read
          HttpHeader="";
          //stopping client
          client.stop();
        }
      }
    }

  }
}