library Ethernet;
{ To avoid using sharemempass string information using PChar or ShortString parameters. }
uses
FastMM4 in 'FastMM4.pas',
SysUtils,
Classes,
dataUnit in 'dataUnit.pas' {DataModule1: TDataModule};

{$R *.res}

function Initalise: integer; stdcall;
begin
result := 0;
// The following line was missing from the original code and this caused most of the 
//problem I belive it moust also be implictly freed.

DataModule1 := TDataModule1.Create(nil); // creates the data module
 
MemRecv := TStringList.Create; // create a string list to hold recived messages
memrecv.Add('Test line');
end;

function StopAll: integer; stdcall;
begin
result := 0;
try
Freeandnil(Memrecv);
Datamodule1.Server.Active := false;
datamodule1.Client.Active := false;
except
result := 1;
end;
end;

function ActivateServer(LocalP: shortstring;
remoteH: shortstring;
RemoteP: shortstring): integer; stdcall;
begin
result := 0;
with DataModule1 do
try
// any one of these calls cause the app to hang!!
Client.RemoteHost := RemoteH;
Client.RemotePort := RemoteP;
Server.LocalPort := LocalP;
Server.Active := True;
except
result := 1;
end;
end;

// read the first line out of the stringlist and delete it!!
// this works as expeceted.

function ReadLine: shortstring; stdcall;
begin
if MemRecv.Count > 0 then
begin
result := MemRecv.Strings[0];
Memrecv.Delete(0);
end
else
result := 'NO DATA';

end;

// new fuction retives the values from the components this works ok.
function RetrieveSettings(Code: integer): shortstring; stdcall;
begin
   with datamodule1 do
   case code of
   0: result := Server.LocalHost;
   1: result := Server.LocalPort;
   2: result := Client.RemotePort;
   3: result := Client.RemoteHost;
   else result := 'Illegal Code';
   end;
end;


exports
 Initalise, StopAll, ActivateServer, Send, ReadLine,
 Minimum, Maximum, RetrieveSettings, ReadCount;

begin
end;

unit dataUnit;

interface

uses
fastmm4, SysUtils, Sockets, ExtCtrls, Classes;

type
TDataModule1 = class(TDataModule)
Server: TTcpServer;
Client: TTcpClient;
procedure ServerAccept(Sender: TObject;
ClientSocket: TCustomIpClient);
private
{ Private declarations }
public
{ Public declarations }
end;

TClientDataThread = class(TThread)
private
public
ListBuffer :TStringList;
TargetList :TStrings;
procedure synchAddDataToControl;
constructor Create(CreateSuspended: Boolean);
procedure Execute; override;
procedure Terminate;
end;

var
DataModule1: TDataModule1;
Memrecv: Tstringlist;
implementation

{$R *.dfm}

//------------- TClientDataThread impl -----------------------------------------
constructor TClientDataThread.Create(CreateSuspended: Boolean);
begin
inherited Create(CreateSuspended);
FreeOnTerminate := true;
ListBuffer := TStringList.Create;
end;

procedure TClientDataThread.Terminate;
begin
ListBuffer.Free;
inherited;
end;

procedure TClientDataThread.Execute;
begin
Synchronize(synchAddDataToControl);
end;

procedure TClientDataThread.synchAddDataToControl;
begin
TargetList.AddStrings(ListBuffer);
end;

//------------- end TClientDataThread impl -------------------------------------


procedure TDataModule1.ServerAccept(Sender: TObject;
ClientSocket: TCustomIpClient);
var
s: string;
DataThread: TClientDataThread;
begin
// create thread
DataThread:= TClientDataThread.Create(true);
// set the TagetList to the output string list.
DataThread.TargetList := memRecv;

// Load the Threads ListBuffer
DataThread.ListBuffer.Add('*** Connection Accepted ***');
DataThread.ListBuffer.Add('Remote Host: ' + ClientSocket.LookupHostName(ClientSocket.RemoteHos t) +
' (' + ClientSocket.RemoteHost + ')');
DataThread.ListBuffer.Add('===== Begin message =====');
s := ClientSocket.Receiveln;
while s <> '' do
begin
DataThread.ListBuffer.Add(s);
s := ClientSocket.Receiveln;
end;
DataThread.ListBuffer.Add('===== End of message =====');

// Call Resume which will execute and synch the
// ListBuffer with the TargetList
DataThread.Resume;
end;

end.

...
 var 
  SomeForm: TForm;

function CreateSomeForm: Pointer;
begin
 Result := SomeForm.Create(nil);
 ...
 // some other code
end;

procedure DestroySomeForm;
begin
 If Assigned(SomeForm) then SomeForm.Free;
 ...
 // some other code
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  try
     if Initalise > 0 then
       showmessage('Initalisation Error')
     else
       MessageBox.Text := 'Init OK';
  except
     showmessage('Error in Dll');
  end;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
   try
      MessageBox.Text := inttostr(Maximum(10,20));
   except
       showmessage('Error in Dll');
   end;
end;

procedure TForm1.SetupBtnClick(Sender: TObject);
begin
  if ActivateServer(strtoint(LocalPort.Text), Address.Text, strtoint(RemotePort.Text)) = 0 then
      MessageBox.Text := 'Server active';
  IpCheck.Enabled := true;
end;

procedure TForm1.ClosebtnClick(Sender: TObject);
begin
  ipcheck.Enabled := false;
  close
end;

procedure TForm1.ReadBtnClick(Sender: TObject);
begin
  MessageBox.Text := ReadLine;
  RemCount.Caption := inttostr(ReadCount);
end;

procedure TForm1.SendBtnClick(Sender: TObject);
begin
   if send(OutputBox.Text, trim(address.Text), strtoint(trim(remotePort.Text))) = 0 then
       messagebox.Text := 'Client connected';
   BSent.Caption := inttostr(ClientBytesSent);
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  try
     if Initalise > 0 then
       showmessage('Initalisation Error')
     else
       MessageBox.Text := 'Init OK';
  except
     showmessage('Error in Dll');
  end;
end;