Сделать загрузчик приложения через TCP

{ 
Loading Delphi apps without a browser and on Win as Linux as well needs a 
decision once. 
With a loader on the client side, no further installation is in charge. 
We had the requirement starting different Delphi apps from a 
linux or windows server, wherever you are. 
We call it Delphi Web Start (DWS). 
The dws-client gets a list and after clicking on it, the app is 
loading from server to client with just a stream. 
First we had to choose between a ftp and a tcp solution. The 
advantage of tcp is the freedom to define a separate port, which 
was "services, port 9010 - DelphiWebStart". 
You will need indy. Because it is simple to use and very fast. 
The tcp-server comes from indy which has one great advantage: 


CommandHandlers is a collection of text commands that will be 
processed by the server. This property greatly simplify the 
process of building servers based on text protocols. 


First we start with DWS_Server, 
so we define two command handlers: 
}

 CTR_LIST = 'return_list';
 CTR_FILE = 'return_file';

 { 
By starting the tcp-server it returns with the first command 
handler "CTR_LIST" a list of the apps: 
}

 procedure
 TForm1.IdTCPServer1Execute(AThread: TIdPeerThread);
 ...
 // comes with writeline from client 
if
 sRequest = CTR_LIST then
 begin

   for
 idx:= 0 to
 meData.Lines.Count - 1 do

   athread.Connection.WriteLn(ExtractFileName(meData.Lines[idx]));
   aThread.Connection.WriteLn('::END::');
   aThread.Connection.Disconnect;


 { 
One word concerning the thread: 
In the internal architecture there are 2 threads categories. 

First is a listener thread that "listen" and waits for a 
connection. So we don't have to worry about threads, the built in 
thread will be served by indy though parameter: 
}

 IdTCPServer1Execute(AThread: TIdPeerThread)

 { 
When our dws-client is connected, this thread transfer all the 
communication operations to another thread. 
This technique is very efficient because your client application 
will be able to connect any time, even if there are many 
different connections to the server. 
}


 //The second command "CTR_FILE" transfers the app to the client: 
if
 Pos(CTR_FILE, sRequest) > 0 then
 begin

     iPos := Pos(CTR_FILE, sRequest);
     FileName := GetFullPath(FileName);
     if
 FileExists(FileName) then
 begin

       lbStatus.Items.Insert(0, Format('%-20s %s',
         [DateTimeToStr(now), 'Transfer starts ...']));
      FileStream := TFileStream.Create(FileName, fmOpenRead +
      fmShareDenyNone);
      aThread.Connection.OpenWriteBuffer;
      aThread.Connection.WriteStream(FileStream);
      aThread.Connection.CloseWriteBuffer;
      FreeAndNil(FileStream);
      aThread.Connection.Disconnect;


 { 
Now let's have a look at the client side. The client connects to 
the server, using the connect method of TIdTcpClient. In this 
moment, the client sends any command to the server, in our case 
(you remember DelphiWebStart) he gets the list of available apps: 
}

     with
 IdTCPClient1 do
 begin

       if
 Connected then
 DisConnect;
       showStatus;
       Host:= edHost.Text;
       Port:= StrToInt(edPort.Text);
       Connect;
       WriteLn(CTR_LIST);

 //After clicking on his choice, the app will be served: 

with
 IdTCPClient1 do
 begin

 ExtractFileName(lbres.Items[lbres.ItemIndex])]));
 WriteLn(CTR_FILE + lbres.Items[lbres.ItemIndex]);
 FileName:= ExpandFileName(edPath.Text + '/' +
 ExtractFileName(lbres.Items[lbres.ItemIndex]));
 ...
 FileStream := TFileStream.Create(FileName, fmCreate);
    while
 connected do
 begin

      ReadStream(FileStream, -1, true);
   ....
     {$IFDEF LINUX}
         execv(pchar(filename),NIL
);
       //libc.system(pchar(filename)); 
     {$ENDIF}
      {$IFDEF MSWINDOWS}
      // shellapi.WinExec('c:testcua.bat', SW_SHOW); 
     with
 lbstatus.items do
 begin

        case
  shellapi.shellExecute(0,'open', pchar(filename), '',NIL
,
                     SW_SHOWNORMAL) of

          0: insert(0, 'out of memory or resources');
          ERROR_BAD_FORMAT: insert(0, 'file is invalid in image');
          ERROR_FILE_NOT_FOUND: insert(0,'file was not found');
          ERROR_PATH_NOT_FOUND: insert(0,'path was not found');
        end
;
        Insert(0, Format('%-20s %s',
                [DateTimeToStr(now), filename + ' Loaded...']));
      end

      {$ENDIF}

 { 
One note about execution on linux with libc-commands; there will 
be better solutions (execute and wait and so on) and we still 

work on it, so I'm curious about comments on 

   "Delphi Web Start" 

therfore my aim is to publish improvments in a basic framework on 
sourceforge.net depends on your feedback ;) 

Many thanks to Dr. Karlheinz Morth with a first glance. 

Test your server with the telnet program. Type telnet 
hostname:9010 and then: 'return_list' and you'll get the list 
from the apps you defined in a txt-file on the server. 
}

 meData.Lines.LoadFromFile(ExpandFileName(FILE_PATH));

 { 
I know that we haven't implement an error handling procedure, 
but for our scope this example is almost 
sufficient. 
Code is available: http://max.kleiner.com/download/dws.zip 
}

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