// =============== making a package to send ==================
byte[] sendPackage = new byte[512]; // package to send
byte[] isLast = new byte[1]; // indicated the package is the last one or
not
byte[] checkSum = new byte[20];
byte[] size = new byte[3]; //holds the size of data
byte[] seqNumber = new byte[3]; // holds the sequence number for the package
byte[] data = new byte[505]; //485 holds the data to send
