Arduino -> Processing hacking SerialCallResponse

Ok, sorry for not providing much detail.

Before I paste the code out fully, I think the issue might be exactly what you said: I'm reading the rfid through serial and trying to communicate with Processing through Serial. However, I am able to read the secondSensor in Processing fine. I don't understand why I can read one of the data streams, but not the other?

This is my Arduino code, which shows how its connected:

/*
  Serial Call and Response
 Language: Wiring/Arduino
 
 This program sends an ASCII A (byte of value 65) on startup
 and repeats that until it gets some data in.
 Then it waits for a byte in the serial port, and 
 sends three sensor values whenever it gets a byte in.
 
 Thanks to Greg Shakar and Scott Fitzgerald for the improvements
 
   The circuit:
 * potentiometers attached to analog inputs 0 and 1 
 * pushbutton attached to digital I/O 2
 
 Created 26 Sept. 2005
 by Tom Igoe
 modified 24 April 2012
 by Tom Igoe and Scott Fitzgerald

 This example code is in the public domain.

 http://www.arduino.cc/en/Tutorial/SerialCallResponse

 */
int  val = 0; 
char code[10]; 
int bytesread = 0; 

String RFIDTAG="";
String DisplayTAG="";

int firstSensor = 4;    // first analog sensor
int secondSensor = 0;   // second analog sensor
int trackNum = 0;
int inByte = 0;         // incoming serial byte

void setup()
{
  // start serial port at 9600 bps:
  Serial.begin(2400);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for Leonardo only
  }

  pinMode(2, OUTPUT);   // digital sensor is on digital pin 2
  digitalWrite(2, LOW);
 
  establishContact();  // send a byte to establish contact until receiver responds 
}

void loop()
{
  // if we get a valid byte, read analog ins:
  if (Serial.available() > 0) {
    // get incoming byte:
    inByte = Serial.read();
    
    ReadSerial(RFIDTAG);
    if (RFIDTAG == "190035D511"){
          trackNum = 1;
        } 
    if (RFIDTAG == "3600095756"){
          trackNum = 2;
        }
    if (RFIDTAG == "190035E473"){
          trackNum = 3;
        }
    if (RFIDTAG == "17007EFC59"){
          trackNum = 4;
        }
    //firstSensor = 115;
    //secondSensor = 111;
    //thirdSensor = 533;  
    // send sensor values:
    //Serial.write(firstSensor);
    firstSensor = trackNum;
    Serial.write(firstSensor);
    Serial.write(secondSensor);
    secondSensor ++;
    //Serial.write(thirdSensor);
  }
  
  if(DisplayTAG!=RFIDTAG)
  {
    DisplayTAG=RFIDTAG;
    Serial.println(RFIDTAG);
  }
  
}

void establishContact() {
  while (Serial.available() <= 0) {
    Serial.print('A');   // send a capital A
    delay(300);
  }
}

void ReadSerial(String &ReadTagString)
{
  
  int bytesread = 0;
  int  val = 0; 
  char code[10];
  String TagCode="";

  if(Serial.available() > 0) {          // If data available from reader 
    if((val = Serial.read()) == 10) {   // Check for header 
      bytesread = 0; 
      while(bytesread<10) {                 // Read 10 digit code 
        if( Serial.available() > 0) { 
          val = Serial.read(); 
          if((val == 10)||(val == 13)) {   // If header or stop bytes before the 10 digit reading 
            break;                         // Stop reading 
          } 
          code[bytesread] = val;           // Add the digit           
          bytesread++;                     // Ready to read next digit  
        } 
      } 
      if(bytesread == 10) {                // If 10 digit read is complete 

        for(int x=0;x<10;x++)              //Copy the Chars to a String
        {
          TagCode += code[x];
        }
        ReadTagString = TagCode;          //Update the caller
        while(Serial.available() > 0)     //Burn off any characters still in the buffer
        {
          Serial.read();
        } 
        //compare serial read to tag code
      } 
      bytesread = 0;
      TagCode="";
    } 
  } 
}

And this is my Processing code:

// This example code is in the public domain.

import processing.serial.*;

int bgcolor;           // Background color
int fgcolor;           // Fill color
Serial myPort;                       // The serial port
int[] serialInArray = new int[2];    // Where we'll put what we receive
int serialCount = 0;                 // A count of how many bytes we receive
int rfid, rotary;                 // Starting position of the ball
boolean firstContact = false;        // Whether we've heard from the microcontroller

void setup() {
  size(256, 256);  // Stage size
  noStroke();      // No border on the next thing drawn

  // Set the starting position of the ball (middle of the stage)
  

  // Print a list of the serial ports, for debugging purposes:
  println(Serial.list());

  // I know that the first port in the serial list on my mac
  // is always my  FTDI adaptor, so I open Serial.list()[0].
  // On Windows machines, this generally opens COM1.
  // Open whatever port is the one you're using.
  String portName = Serial.list()[0];
  myPort = new Serial(this, portName, 2400);
}

void draw() {
  background(bgcolor);
  fill(fgcolor);
  
}

void serialEvent(Serial myPort) {
  // read a byte from the serial port:
  int inByte = myPort.read();
  // if this is the first byte received, and it's an A,
  // clear the serial buffer and note that you've
  // had first contact from the microcontroller. 
  // Otherwise, add the incoming byte to the array:
  if (firstContact == false) {
    if (inByte == 'A') { 
      myPort.clear();          // clear the serial port buffer
      firstContact = true;     // you've had first contact from the microcontroller
      myPort.write('A');       // ask for more
    } 
  } 
  else {
    // Add the latest byte from the serial port to array:
    serialInArray[serialCount] = inByte;
    serialCount++;

    // If we have 2 bytes:
    if (serialCount > 1 ) {
      rfid = serialInArray[0];
      rotary = serialInArray[1];
      //fgcolor = serialInArray[2];

      // print the values (for debugging purposes only):
      println(rfid + "\t" + rotary + "\t");

      // Send a capital A to request new sensor readings:
      myPort.write('A');
      // Reset serialCount:
      serialCount = 0;
    }
  }
}