An Application Loader with a TCPServer

Problem/Question/Abstract:

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.

Answer:

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);
{   .... }
execv(pchar(filename), nil);

Better with a compiler directive to load delivered files:

{$IFDEF LINUX}
execv(pchar(filename), nil);
//libc.system(pchar(filename));
{$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}

The datastructure is a direct file access. In this case, rather than populating a stand-alone memory structure, the data is written to the StringGrid (which is serving both as a memory structure for holding the data and as a visual control for navigating and editing the data).

type
TAppData = record
Name: string[50];
Size: longint;
Release: string[30];
descript: string[80];
end;

TBuildAppGrid = class(TObject)
private
aGrid: TStringGrid;
app: TAppData;
f: file of TAppData;
FaDatfile: ShortString;
Fmodified: Boolean;
protected
function GetaDatfile: ShortString;
procedure SetaDatfile(const Value: ShortString);
public
constructor initGrid(vGrid: TStringGrid; vFile: shortString);
procedure fillGrid;
procedure storeGrid;
property aDatfile: ShortString read GetaDatfile write SetaDatfile;
property modified: Boolean read Fmodified write Fmodified;
end;

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 M�rth with a first glance.

Test your server with the telnet program. After connecting with host, type "return_list" and you'll see a first result. I know that we haven't implement an error handling procedure, but for our scope this example is almost sufficient. The DWS-source holds version 0.9.

28.10.03 Project DWS is now under Sourceforge: http://sourceforge.net/projects/delphiwebstarthttp://sourceforge.net/projects/delphiwebstart

Component Download: http://max.kleiner.com/download/dws.ziphttp://max.kleiner.com/download/dws.zip