i think something is wrong in his software.

this is my c struct for an artnet packet from their spec

typedef struct ONE_ARTNETDMX_PACKET
{
char ID[ 8 ];
unsigned short OpCode;
unsigned short ProtVer;
unsigned char Sequence;
unsigned char PhysicalPortIndex;
unsigned char Universe;
unsigned char UniverseHi; //docs says this is unused
unsigned short Length;
unsigned char Data[ 512 ];
};