如果用UDP进行网络广播？？

没试过:
TCP/IP是这样规定的:
要实现广播,就要把目的地的IP地址全部置1.
例如你的IP是: 192.168.0.1
要向内部广播, 目的地址就是 192.168.255.255
试试看.

向内部广播, 目的地址就是 192.168.111.255
UDP控件向所有的192.168.111段广播

Wnyu(创业 -- 第一个目标是开一家软件公司) 的方法不错，感觉可以我也没试过，凑热闹来了：）

广播有两种，一种是directed broadcast，
比如你的网段是192.168.0.X
你就往192.168.0.255发就可以了另一种是limited broadcast,
就是把UDP设成广播IP，一般是255.255.255.255
var
  broadcast:bool;
broadcast:=true;
SetSockopt(FSocket,SOL_SOCKET,SO_BROADCAST, @broadcast,sizeof(broadcast));两者都是可以的。
directed broadcast不需要SetSockopt()，以标准的C类网为例，直接发送x.x.x.255就可以了，
这种广播只有同一逻辑子网中的机器才能收到，也就是说对方地址应该是x.x.x.y，如果不是
即使在同一物理子网中也是收不到的。当然，这和子网掩码有关。limited broadcast必须有SetSockopt(FSocket,SOL_SOCKET,SO_BROADCAST, @broadcast,sizeof(broadcast));
它的广播地址是255.255.255.255，它的好处是只要在同一子网中的主机，就可以收到这种
广播，而不必非要在统一逻辑子网中，例如，如果你的地址是x.x.x.1，那么这种广播，
地址是x.y.z.a的主机也能收到。下面是用socket API实现limited broadcast的一个例子：
unit udp;interfaceuses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs, winsock,
  StdCtrls;const
  WM_SOCK = WM_USER + 1;     //自定义windows消息
  UDPPORT = 6543;            //设定UDP端口号
  //INADDR_ALLHOSTS_GROUP = u_long($e0000001);   //D类地址224.0.0.1
(*
* Argument structure for IP_ADD_MEMBERSHIP and IP_DROP_MEMBERSHIP.
* Delphi5自带的winsock.pas中没有ip_mreq的定义。
*){type
  ip_mreq = record
    imr_multiaddr: in_addr;  (* IP multicast address of group *)
    imr_interface: in_addr;  (* local IP address of interface *)
  end;}type
  Tfrmmain = class(TForm)
    Button1: TButton;
    Edit1: TEdit;
    Memo1: TMemo;
    Edit2: TEdit;
    Label1: TLabel;
    Label2: TLabel;
    Label3: TLabel;
    procedure FormCreate(Sender: TObject);
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
    s: TSocket;
    addr: TSockAddr;
    FSockAddrIn : TSockAddrIn;
    //mreq:ip_mreq;
    //利用消息实时获知UDP消息
    procedure ReadData(var Message: TMessage); message WM_SOCK;
  public
    { Public declarations }
    procedure SendData(Content: String);
  end;var
  frmmain: Tfrmmain;implementation{$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);
          //exit;
     end;
     //发送方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;     optval:= 1;
     if setsockopt(s,SOL_SOCKET,SO_BROADCAST,pchar(@optval),sizeof(optval)) = SOCKET_ERROR then
     begin
       showmessage('无法进行UDP广播');
     end;     {mreq.imr_multiaddr.S_addr := INADDR_ALLHOSTS_GROUP;
     mreq.imr_interface.S_addr := INADDR_ANY;
     if setsockopt(s,IPPROTO_IP,IP_ADD_MEMBERSHIP,pchar(@mreq),sizeof(mreq)) = SOCKET_ERROR then
     begin
       showmessage('无法进行UDP组播');
     end;}
     WSAAsyncSelect(s, frmmain.Handle , WM_SOCK, FD_READ);
     //接收端SockAddrIn设定
     FSockAddrIn.SIn_Family := AF_INET;
     FSockAddrIn.SIn_Port := htons(UDPPORT);     label3.Caption := '端口：'+inttostr(UDPPORT);
end;procedure Tfrmmain.FormClose(Sender: TObject; var Action: TCloseAction);
begin
    CloseSocket(s);
end;procedure Tfrmmain.ReadData(var Message: TMessage);
var
   buffer: Array [1..4096] of char;
   len: integer;
   flen: integer;
   Event: word;
   value: string;
begin
     flen:=sizeof(FSockAddrIn);
     FSockAddrIn.SIn_Port := htons(UDPPORT);
     Event := WSAGetSelectEvent(Message.LParam);
     if Event = FD_READ then
     begin
          len := recvfrom(s, buffer, sizeof(buffer), 0, FSockAddrIn, flen);
          value := copy(buffer, 1, len);
          Memo1.Lines.add(value)
     end;
end;procedure Tfrmmain.SendData(Content: String);
var
   value{,hostname}: string;
   len: integer;
begin
     FSockAddrIn.SIn_Addr.S_addr := INADDR_BROADCAST;
     //FSockAddrIn.SIn_Addr.S_addr := inet_addr(pchar(Edit1.text)); //INADDR_BROADCAST;   //INADDR_BROADCAST = -1 ?
     value := Content;
     len := sendto(s, value[1], Length(value), 0, FSockAddrIn, sizeof(FSockAddrIn));
     if (WSAGetLastError() <> WSAEWOULDBLOCK) and (WSAGetLastError() <> 0) then
        showmessage(inttostr(WSAGetLastError()));
     if len = SOCKET_ERROR then
        showmessage('send fail');
     if len <> Length(value) then
        showmessage('Not Send all');
end;procedure Tfrmmain.Button1Click(Sender: TObject);
begin
     senddata(Edit2.text);
end;end.

调试易

如果用UDP进行网络广播？？

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