Eddy Arduino Serial

if(Serial.available() >= 4)
{
  Header = Serial.read()
  // check header

  PacketInfo = Serial.read();
 
  Payload = Serial.read();

  Footer = Serial.read();

  while(Serial.available())
  {
    Serial.read(); // Flush extra bytes
  }

  Byte chksum = generateCheckshum(Header, PacketInfo, Payload, Footer);

  Serial.write(chksum);
}