IP地址
DestPort = 4321;        file://目的端口

Max_Message = 4068;
Max_Packet = 4096;

type

TPacketBuffer = Array[0..Max_Packet-1] of byte;

TForm1 = class(TForm)
Button1: TButton;
Memo1: TMemo;
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
procedure SendIt;
end;

// IP 头
type
T_IP_Header = record
ip_verlen : Byte;
ip_tos : Byte;
ip_totallength : Word;
ip_id : Word;
ip_offset : Word;
ip_ttl : Byte;
ip_protocol : Byte;
ip_checksum : Word;
ip_srcaddr : LongWord;
ip_destaddr : LongWord;
end;

// UDP 头
Type
T_UDP_Header = record
src_portno : Word;
dst_portno : Word;
udp_length : Word;
udp_checksum : Word;
end;

// 一些 Winsock 2 的类型声明
u_char = Char;
u_short = Word;
u_int = Integer;
u_long = Longint;

SunB = packed record
s_b1, s_b2, s_b3, s_b4: u_char;
end;
SunW = packed record
s_w1, s_w2: u_short;
end;
in_addr = record
case integer of
0: (S_un_b: SunB);
1: (S_un_w: SunW);
2: (S_addr: u_long);
end;
TInAddr = in_addr;
Sockaddr_in = record
case Integer of
0: (sin_family: u_short;
sin_port: u_short;
sin_addr: TInAddr;
sin_zero: array[0..7] of Char);
1: (sa_family: u_short;
sa_data: array[0..13] of Char)
end;
TSockAddr = Sockaddr_in;
TSocket = u_int;

const
WSADESCRIPTION_LEN = 256;
WSASYS_STATUS_LEN = 128;

type
PWSAData = ^TWSAData;
WSAData = record //  WSDATA
wVersion: Word;
wHighVersion: Word;
szDescription: array[0..WSADESCRIPTION_LEN] of Char;
szSystemStatus: array[0..WSASYS_STATUS_LEN] of Char;
iMaxSockets: Word;
iMaxUdpDg: Word;
lpVendorInfo: PChar;
end;
TWSAData = WSAData;

file://定义一些 winsock 2 函数
function closesocket(s: TSocket): Integer; stdcall;
function socket(af, Struct, protocol: Integer): TSocket; stdcall;
function sendto(s: TSocket; var Buf; len, flags: Integer; var addrto: TSockAddr;
tolen: Integer): Integer; stdcall;{}
function setsockopt(s: TSocket; level, optname: Integer; optval: PChar;
optlen: Integer): Integer; stdcall;
function inet_addr(cp: PChar): u_long; stdcall; {PInAddr;} { TInAddr }
function htons(hostshort: u_short): u_short; stdcall;
function WSAGetLastError: Integer; stdcall;
function WSAStartup(wVersionRequired: word; var WSData: TWSAData): Integer; stdcall;
function WSACleanup: Integer; stdcall;

const
AF_INET = 2; // internetwork: UDP, TCP, etc.

IP_HDRINCL = 2; // IP Header Include

SOCK_RAW = 3; // raw-protocol interface

IPPROTO_IP = 0; // dummy for IP
IPPROTO_TCP = 6; // tcp
IPPROTO_UDP = 17; // user datagram protocol
IPPROTO_RAW = 255; // raw IP packet

INVALID_SOCKET = TSocket(NOT(0));
SOCKET_ERROR = -1;

var
Form1: TForm1;

implementation

// Import Winsock 2 functions
const WinSocket = ''WS2_32.DLL'';

function closesocket; external winsocket name ''closesocket'';
function socket; external winsocket name ''socket'';
function sendto; external winsocket name ''sendto'';
function setsockopt; external winsocket name ''setsockopt'';
function inet_addr; external winsocket name ''inet_addr'';
function htons; exter