udp接收到的数据包不完整

Question

//客户端
var
    leftsize:integer;
    sendsize:integer;
    streamsize:integer;
    bufsize:integer;
    sendstream:tmemorystream;
    stream:tmemorystream;
procedure TForm1.Button2Click(Sender: TObject);
begin
  form1.screencap(0,0,100,100);//截屏,数据存在stream里
  streamsize:=stream.Size;
  leftsize:=streamsize;
  bufsize:=form1.IdUDPClient1.BufferSize;//form1.IdUDPClient1.BufferSize=2048
  form1.IdUDPClient1.Active:=true;
  sendstream:=tmemorystream.Create;
  while leftsize>0 do
   begin
    if(leftsize>bufsize) then
    begin
     leftsize:=leftsize-bufsize;
     sendsize:=bufsize;
    end
    else
    begin
     sendsize:=leftsize;
      leftsize:=0;
    end;
    sendstream.CopyFrom(stream,sendsize);     
    form1.Memo1.Lines.Add(inttostr(sendsize)+'  '+inttostr(stream.Position) );//记录发送的数据，结果显示全部发出去了
    sendstream.Position:=0;
    form1.IdUDPClient1.SendBuffer('127.0.0.1',2000,sendstream.Memory^,sendsize);
   end;
   sendstream.Clear;
   stream.Clear;
end;//服务端
var
  tmpstream:TStringStream;
procedure TForm1.Button3Click(Sender: TObject);
begin
form1.IdUDPServer1.DefaultPort:=2000;
tmpstream:=TStringStream.Create('');
form1.IdUDPServer1.Active:=true;
end;procedure TForm1.IdUDPServer1UDPRead(Sender: TObject; AData: TStream;
  ABinding: TIdSocketHandle);
begin  try
    tmpstream.CopyFrom(adata,adata.Size);
    if adata.Size<form1.IdUDPServer1.BufferSize then
    begin
       tmpstream.Position:=0;
       form1.Image1.Picture.Bitmap.LoadFromStream(tmpstream);
    end;
  except
    showmessage('except');
  end;  form1.Memo2.Lines.Add(inttostr(adata.Size));//记录接收到的数据包，结果显示只接收到部份数据包
end;

Answer 1

// 如果把客房端修改成如下，服务端就能正常显示 ，不知道为什么，求助!!!
var
    leftsize:integer;
    sendsize:integer;
    streamsize:integer;
    bufsize:integer;
    sendstream:tmemorystream;
    stream:tmemorystream;
procedure TForm1.Button2Click(Sender: TObject);
begin
  form1.screencap(0,0,100,100);//截屏,数据存在stream里
  streamsize:=stream.Size;
  leftsize:=streamsize;
  bufsize:=form1.IdUDPClient1.BufferSize;//form1.IdUDPClient1.BufferSize=2048
  form1.IdUDPClient1.Active:=true;
  sendstream:=tmemorystream.Create;
  form1.Timer1.Enabled:=true;
end;procedure TForm1.Timer1Timer(Sender: TObject);
begin
if(leftsize>bufsize) then
 begin
leftsize:=leftsize-bufsize;
sendsize:=bufsize;
 end
 else
 begin
sendsize:=leftsize;
  leftsize:=0;
 end;
sendstream.CopyFrom(stream,sendsize);
form1.Memo1.Lines.Add(inttostr(stream.Position) );
sendstream.Position:=0;
form1.IdUDPClient1.SendBuffer('127.0.0.1',2000,sendstream.Memory^,sendsize);
if(leftsize=0) then
begin
  form1.Timer1.Enabled:=false;
  stream.Clear;
end;
end;

Answer 2

socket缓冲区的大小有限制，建议每个UDP包不超过4K,每个包的间隔>10ms即可，可以封装一个发送线程。另外，对UDP这么简单的通信，就不要用什么组件了，直接用API，清楚直接。