Arduino Uno I2C with (motorshield) in Matlab

I have tried to add the Wire library to the srv.pde to establish an I2C,

The slave code:

#include <Wire.h>

void setup()
{
Wire.begin(100);
Wire.onReceive(receiveEvent);
}

void loop()
{
}

void receiveEvent( int howMany)
{
while (Wire.available())
{
}
}

The master code, is the srv.pde and I added:
#include <Wire.h>
#include <AccelStepper.h>

and to the void loop(), I added

Wire.beginTransmission (100);

Do I need to end the transmission (I mean add Wire.endTransmission() to the code)? Or the transmission should automatically end when I disconnect the arduino?

Adding #include <AccelStepper.h> to the code didn't seem to have an effect, the 2 motors still don't run simultaneously. What do I have to do to fix this?