这样的问题已经回答好多次了，请搜索关键词“局域网”或“工作组”或者直接点类别
INTENET，都可以看到这样的例子。
Delphi源码如下，其中UDP用Socket API实现。
-------------------------------------------------------
unit udp;
interface
uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs, winsock,
StdCtrls;
const
WM_SOCK = WM_USER + 1; //自定义windows消息
UDPPORT = 6767; //设定UDP端口号
NBTPORT = 137;
type
Tfrmmain = class(TForm)
Button1: TButton;
ListBox1: TListBox;
Edit1: TEdit;
procedure FormCreate(Sender: TObject);
procedure FormClose(Sender: TObject; var Action: TCloseAction);
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
s: TSocket;
addr: TSockAddr;
FSockAddrIn : TSockAddrIn; //利用消息实时获知UDP消息
procedure ReadData(var Message: TMessage); message WM_SOCK;
public
{ Public declarations }
procedure SendData(b:array of byte);
end;
var
frmmain: Tfrmmain;
implementation
{$R *.DFM}
procedure Tfrmmain.FormCreate(Sender: TObject);
var
TempWSAData: TWSAData;
//optval: integer;
begin
// 初始化SOCKET
if WSAStartup($101, TempWSAData)=1 then
showmessage('StartUp Error!');
s := Socket(AF_INET, SOCK_DGRAM, 0);
if (s = INVALID_SOCKET) then //Socket创建失败
begin
showmessage(inttostr(WSAGetLastError())+' Socket创建失败');
CloseSocket(s);
end;
//本机SockAddr绑定
addr.sin_family := AF_INET;
addr.sin_addr.S_addr := INADDR_ANY;
addr.sin_port := htons(UDPPORT);
if Bind(s, addr, sizeof(addr)) <> 0 then
begin
showmessage('bind fail');
end;
WSAAsyncSelect(s, frmmain.Handle , WM_SOCK, FD_READ);
//对方SockAddrIn设定
FSockAddrIn.SIn_Family := AF_INET;
FSockAddrIn.SIn_Port := htons(NBTPORT);
end;
procedure Tfrmmain.FormClose(Sender: TObject; var Action: TCloseAction);
begin
CloseSocket(s);
end;
procedure GetInfo(buf: Array of byte);
{这个过程是根据返回报文的内容凑出来的，偶尔会出错。如果能根据
报文格式的定义来做（可查阅相关RFC文档，可惜我没时间，以后做吧），就更好了。
如果你作出来了，不妨寄给我一个哟。e-mail:zw84611@sina.com}
var bAdd,bMac:boolean;
str,strHost,strHex,strMac:string;
tem,i,j:integer;
begin
bAdd:=true;
strHost:='';
strHex:='';
tem:=0;
for i:=57 to 500 do //57-72
begin
if(Buf=$cc)then break;
if(Buf=$20)then bAdd:=false;
if(bAdd)then
begin
str:=char(Buf);
strHost:=strHost+str;
str:=Format('%x.',[Buf]);
strHex:=strHex+str;
end;
inc(tem);
if(tem mod 18=0)then
begin
bAdd:=true;
Trim(strHex);
bMac:=true;
for j:=1 to length(strHex) do if strHex[j]>'0' then bMac:=false;
//showmessage(strHex);
if(bMac)then
with frmmain.ListBox1 do
begin
Items.Delete(items.count-1);
Items.add('mac address:');
Delete(strMac,17,length(strMac)-17);
Items.Add(strMac);
break;
end;
frmmain.ListBox1.items.Add(strHost);
strMac:=strHex;
strHost:='';
strHex:='';
end;
end;
end;
procedure Tfrmmain.ReadData(var Message: TMessage);
var
buffer: Array [1..500] of byte;
len{,i}: integer;
flen: integer;
Event: word;
value: string;
begin
value:='';
Event := WSAGetSelectEvent(Message.LParam);
if Event = FD_READ then
begin
len := recvfrom(s, buffer, sizeof(buffer), 0, FSockAddrIn, flen);
{for i:=1 to len do value:=value+format('%x',[buffer]);
ListBox1.items.add(value);
value:='';
for i:=1 to len do if char(buffer)<>#0 then value:=value+char(buffer);
ListBox1.items.add(value);}
if len<> 0 then GetInfo(buffer);
end;
end;
procedure Tfrmmain.SendData(b:array of byte);
var
len: integer;
begin
FSockAddrIn.SIn_Addr.S_addr := inet_addr(pchar(edit1.text));
len := sendto(s, b[0],50, 0, FSockAddrIn, sizeof(FSockAddrIn));
//if (WSAGetLastError() <> WSAEWOULDBLOCK) and (WSAGetLastError() <> 0) then showmessage(inttostr(WSAGetLastError()));
if len = SOCKET_ERROR then
showmessage('send fail');
if len <> 50 then
showmessage('Not Send all');
end;
procedure Tfrmmain.Button1Click(Sender: TObject);
const NbtstatPacket:array[0..49]of byte
=($0,$0,$0,$10,$0,$1,
$0,$0,$0,$0,$0,$0,$20,$43,$4b,
$41,$41,$41,$41,$41,$41,$41,$41,
$41,$41,$41,$41,$41,$41,$41,$41,
$41,$41,$41,$41,$41,$41,$41,$41,
$41,$41,$41,$41,$41,$41,$0,$0,$21,$0,$1);
begin
senddata(NbtstatPacket);
end;
end.
自己慢慢看
