Map Data

// Assuming size.x and size.y are 4 bytes, and heightmap.getHeight( ix, iy ) is 1 byte

// Writing
buffer.writeInt( size.x );
buffer.writeInt( size.y );

for ( int ix = 0; ix < size.x; ++ix )
{
    for ( int iy = 0; iy < size.y; ++iy )
    {
        byte height = heightmap.getHeight( ix, iy );
        buffer.writeByte( height );
    }
}

// Reading
size.x = buffer.readInt();
size.y = buffer.readInt();

for ( int ix = 0; ix < size.x; ++ix )
{
    for ( int iy = 0; iy < size.y; ++iy )
    {
        byte height = buffer.readByte();
        heightmap.setHeight( ix, iy, height );
    }
}