首先新建服务端。
如下图所示建立工程:
代码如下:
unitServerUnit;
interface
uses
Windows,Messages,SysUtils,Variants,Classes,Graphics,Controls,Forms,
Dialogs,IdBaseComponent,IdComponent,IdUDPBase,IdUDPServer,StdCtrls,
IdSocketHandle,IdGlobal;
type
TServerForm=class(TForm)
Label1:TLabel;
Edit1:TEdit;
Label2:TLabel;
Edit2:TEdit;
Label3:TLabel;
Edit3:TEdit;
IdUDPServer1:TIdUDPServer;
procedureIdUDPServer1UDPRead(AThread:TIdUDPListenerThread;AData:TBytes;
ABinding:TIdSocketHandle);
procedureFormCreate(Sender:TObject);
private
{Privatedeclarations}
public
{Publicdeclarations}
end;
var
ServerForm:TServerForm;
implementation
{$R*.dfm}
procedureTServerForm.FormCreate(Sender:TObject);
begin
IdUDPServer1.DefaultPort:=3030;
IdUDPServer1.Active:=True;
Edit1.ReadOnly:=True;
Edit2.ReadOnly:=True;
Edit3.ReadOnly:=True;
end;
procedureTServerForm.IdUDPServer1UDPRead(AThread:TIdUDPListenerThread;
AData:TBytes;ABinding:TIdSocketHandle);
begin
Edit1.Text:=ABinding.PeerIP;
Edit2.Text:=IntToStr(ABinding.PeerPort);
Edit3.Text:=BytesToString(AData);
IdUDPServer1.Send(ABinding.PeerIP,ABinding.PeerPort,TimeToStr(Time)+'=>Serverreceivedthemessage!');
end;
end.
然后新建客户端如下图所示:
注意:为了让客户端能实时监控服务端发回来的确定消息,使用了TTimer控件,Interval设置为250毫秒。
代码如下:
unitClientUnit;
interface
uses
Windows,Messages,SysUtils,Variants,Classes,Graphics,Controls,Forms,
Dialogs,StdCtrls,ExtCtrls,IdBaseComponent,IdComponent,IdUDPBase,
IdUDPClient;
type
TClientForm=class(TForm)
Label1:TLabel;
Edit1:TEdit;
Button1:TButton;
Label2:TLabel;
Edit2:TEdit;
IdUDPClient1:TIdUDPClient;
Timer1:TTimer;
procedureButton1Click(Sender:TObject);
procedureFormCreate(Sender:TObject);
procedureTimer1Timer(Sender:TObject);
private
{Privatedeclarations}
public
{Publicdeclarations}
end;
var
ClientForm:TClientForm;
implementation
{$R*.dfm}
procedureTClientForm.Button1Click(Sender:TObject);
begin
IdUDPClient1.Broadcast(Edit1.Text,3030);
Timer1.Enabled:=True;
end;
procedureTClientForm.FormCreate(Sender:TObject);
begin
Timer1.Enabled:=False;
Edit2.ReadOnly:=True;
end;
procedureTClientForm.Timer1Timer(Sender:TObject);
begin
Edit2.Text:=IdUDPClient1.ReceiveString(-1);
Timer1.Enabled:=False;
end;
end.
如此实现简单的UDP协议下局域网通讯。
===================================================
但是很快我又发现,上面的代码在本机虽然能够正常执行,分别位于2台电脑时会发生无法接收服务器响应的现象。
究其原因可能是客户程序用户界面“冻结”的缘故。
于是在服务端和客户端都加上TIdAntiFreeze以解决上面发生的现象(尤其是客户端)。
服务端:
客户端:
事实上,上述客户端的TTimer控件是完全没有必要使用的。
当我们对IdUDPClient使用Broadcast方法后,一旦与服务端通讯成功,IdUDPClient自动会得到来自服务端的返回值。
如果通讯失败,在IdUDPClient.ReceiveTimeout所设定的事件后终止响应,所以我们可以吧延迟事件稍微设长一点。
于是客户端代码可以简单的写成:
unitClientUnit;
interface
uses
Windows,Messages,SysUtils,Variants,Classes,Graphics,Controls,Forms,
Dialogs,StdCtrls,ExtCtrls,IdBaseComponent,IdComponent,IdUDPBase,
IdUDPClient,IdAntiFreezeBase,IdAntiFreeze;
type
TClientForm=class(TForm)
Label1:TLabel;
Edit1:TEdit;
Button1:TButton;
Label2:TLabel;
Edit2:TEdit;
IdUDPClient1:TIdUDPClient;
IdAntiFreeze1:TIdAntiFreeze;
procedureButton1Click(Sender:TObject);
procedureFormCreate(Sender:TObject);
private
{Privatedeclarations}
public
{Publicdeclarations}
end;
var
ClientForm:TClientForm;
implementation
{$R*.dfm}
procedureTClientForm.Button1Click(Sender:TObject);
begin
IdUDPClient1.Broadcast(Edit1.Text,3030);
Edit2.Text:=IdUDPClient1.ReceiveString(-1);
end;
procedureTClientForm.FormCreate(Sender:TObject);
begin
IdUDPClient1.ReceiveTimeout:=5000;
Edit2.ReadOnly:=True;
end;
end.
如此即可完成与服务端的通讯。
=======================================================================
关于网络中查找服务器主机的问题,似乎可以使用UDP广播的方式查找。
先看代码:
unitClientUnit;
interface
uses
Windows,Messages,SysUtils,Variants,Classes,Graphics,Controls,Forms,
Dialogs,StdCtrls,ExtCtrls,IdBaseComponent,IdComponent,IdUDPBase,
IdUDPClient,IdAntiFreezeBase,IdAntiFreeze;
type
TClientForm=class(TForm)
Label1:TLabel;
Edit1:TEdit;
Button1:TButton;
Label2:TLabel;
IdUDPClient1:TIdUDPClient;
IdAntiFreeze1:TIdAntiFreeze;
ListBox1:TListBox;
Timer1:TTimer;
procedureButton1Click(Sender:TObject);
procedureFormCreate(Sender:TObject);
procedureTimer1Timer(Sender:TObject);
private
{Privatedeclarations}
varIpList:TStringList;
public
{Publicdeclarations}
end;
var
ClientForm:TClientForm;
implementation
{$R*.dfm}
procedureTClientForm.Button1Click(Sender:TObject);
begin
IdUDPClient1.Broadcast(Edit1.Text,3030);
ListBox1.Items.Add(IdUDPClient1.ReceiveString());
end;
procedureTClientForm.FormCreate(Sender:TObject);
begin
IdUDPClient1.ReceiveTimeout:=10000;
IpList:=TStringList.Create;
end;
procedureTClientForm.Timer1Timer(Sender:TObject);
varipaddr:string;
varI:Integer;
begin
IdUDPClient1.BroadcastEnabled:=True;
IdUDPClient1.Broadcast('SearchHost',3030);
ipaddr:=IdUDPClient1.ReceiveString();
ifIpList.IndexOf(ipaddr)=-1then
IpList.Add(ipaddr);
ListBox1.Clear;
forI:=0toIpList.Count-1do
ListBox1.Items.Add(IpList.Strings[I]);
end;
end.
这样在IpList中就会不断的有主机的IP地址被加入进来了。
但是实际情况是这样的:
由于使用了TTimer控件,我这里设置了Interval:5000,如果设置过小会因为线程大量占用而严重影响主程序正常工作,不知道有什么办法来解决这个问题。还有,当网络中没有服务器的任何响应时客户端也会出现假死现象,不知如何解决。