上传单元 (100分)

哪位高手看看下面的代码，错在哪里，为什么这个上传单元会出错？
unit UpLoadUnit;

interface

uses
Classes, IdTCPServer,IdGlobal,ComCtrls,SysUtils;

type
TUpLoadThread = class(TThread)
private
TheFileName:String;
TheFileSize:integer;
SysThread:TIdPeerThread;
protected
procedure Execute; override;
Public
constructor Create(AThread:TIdPeerThread;TFN:String;TheLen:integer);
destructor Destroy; override;
end;

implementation
uses APFUnit,server;

constructor TUpLoadThread.Create(AThread:TIdPeerThread;TFN:String;TheLen:integer);
begin
inherited Create(true);
TheFileName:=TFN;
TheFileSize:=TheLen;
SysThread:=AThread;
FreeOnTerminate:=true;
Suspended := false;
Priority:=tpIDLE;
end;

procedure TUpLoadThread.Execute;
var
SaveFStream:TFileStream;
begin
try
SaveFStream:=TFileStream.Create(TheFileName,fmCreate);
except
SysThread.Terminate;
self.Terminate;
exit;
end;
SaveFStream.Size:=0;
try
SysThread.Connection.ReadStream(SaveFStream,TheFileSize);//好像经常这儿出错，不知道如何改
except
SaveFStream.Free;
SysThread.Terminate;
self.Terminate;
exit;
end;
end;

destructor TUpLoadThread.Destroy;
begin
inherited destroy;
end;
end.

什么错提示

Connection好像没有此方法吧

出现的错误提示是：
存取地址00460FB4违例发生在模块'MM.EXE'中，读在地址00000000里。
其中MM.EXE是程序名称。