typedef struct _UDPHeader
{
     unsigned short     SourcePort;
     unsigned short     DestinationPort;
     unsigned short     Length;
     unsigned short     Checksum;
} UDPHeader;

typedef UDPHeader FAR * LPUDPHeader;
#define UDPHeaderLength sizeof(UDPHeader)

#define tOptionType unsigned char

typedef struct _IPOption
{
      tOptionType   & nbsp;      OptionType;
 
     unsigned char     OptionLength;
     unsigned char     OptionData;
} IPOption;
#define IpOptionLength sizeof(IpOption)

typedef struct _IpHeader 
{
     unsigned  char         &n bsp;HeaderLength_Version;
     unsigned  char         &n bsp;TypeOfService;           // Type of service
     unsigned  short         & nbsp;TotalLength;       & nbsp;  // total length of the 

packet
     unsigned  short         & nbsp;Identification;      &nbs p;   // unique identifier
     unsigned  short         & nbsp;FragmentationFlags; // flags
     unsigned  char         &n bsp;TTL;        &nbs p;         &nbs p; // Time To Live
     unsigned  char         &n bsp;Protocol;       &nbsp ;   // protocol (TCP, UDP etc)
     unsigned  short         & nbsp;CheckSum;       &nbs p;       //  IP Header 

checksum

     unsigned  int         &nb sp;sourceIPAddress;     //  Source address
     unsigned  int         &nb sp;destIPAddress;       & nbsp;  // Destination Address

} IpHeader;

typedef IpHeader FAR * LPIpHeader;

#define IpHeaderLength sizeof(IpHeader)

int sfd;
sfd=socket(AF_INET, SOCK_RAW,IPPROTO_UDP);
int iTrue=1;
setsockopt( sfd, IPPROTO_IP, IP_HDRINCL, (char*)&iTrue,4);
     
LPIpHeader lpHead=new _IpHeader;
lpHead->HeaderLength_Version=77;
//Protocol
lpHead->Protocol=IPPROTO_UDP;
//Fragmentation flags
lpHead->FragmentationFlags=0;
//Time to live
lpHead->TTL=64;
//Checksum - set to 0
lpHead->CheckSum=0;
//Identification
lpHead->Identification=0;//htons(usIdentification);
//Precedence
lpHead->TypeOfService=0;
lpHead->destIPAddress=inet_addr("127.0.0.1");
lpHead->sourceIPAddress= inet_addr("127.0.0.1");

LPUDPHeader lpUDP;
lpUDP=new UDPHeader;

//Set the ports
lpUDP->SourcePort=htons(7777);
lpUDP->DestinationPort=htons(7777);
//Set the length
lpUDP->Length=htons(UDPHeaderLength);

//Check sum
lpUDP->Checksum=0;

int iTotalLength;
iTotalLength=IpHeaderLength+UDPHeaderLength;
char* newBuf=new char[iTotalLength];
memcpy(newBuf,lpHead,IpHeaderLength);
memcpy(newBuf+IpHeaderLength,lpUDP,UDPHeaderLength);
struct sockaddr_in sin;
memset(&sin,0,sizeof(sin));
sin.sin_family=AF_INET;
sin.sin_port=htons(7777);  
sin.sin_addr.s_addr=inet_addr("127.0.0.1");
sendto(sfd,(const char*)newBuf,100,0,(const struct sockaddr*)&sin,sizeof(sin));