diff --git a/StompClient.pas b/StompClient.pas
index ff43e53..65146ea 100644
--- a/StompClient.pas
+++ b/StompClient.pas
@@ -29,18 +29,16 @@ interface
   StompTypes,
   SysUtils,
   DateUtils,
-
+  SyncObjs,
 {$IFNDEF USESYNAPSE}
   IdTCPClient,
   IdException,
   IdExceptionCore,
   IdHeaderList,
   IdIOHandler, IdIOHandlerSocket, IdIOHandlerStack, IdSSL, IdSSLOpenSSL, // SSL
-  System.SyncObjs,
 {$ELSE}
   synsock,
   blcksock,
-
 {$ENDIF}
   Classes;
 
@@ -51,6 +49,16 @@ interface
 
   THeartBeatThread = class;
 
+{$IFDEF USESYNAPSE}
+  IIdString = AnsiString;
+{$ELSE}
+  {$IF CompilerVersion < 24}
+    IIdString = AnsiString;
+  {$ELSE}
+    IIdString = string;
+  {$IFEND}
+{$ENDIF}
+
   TStompClient = class(TInterfacedObject, IStompClient)
   private
 
@@ -91,7 +99,7 @@   TStompClient = class(TInterfacedObject, IStompClient)
     FConnectionTimeout: UInt32;
     FOutgoingHeartBeats: Int64;
     FIncomingHeartBeats: Int64;
-    FLock: TObject;
+    FLock: TCriticalSection;
     FHeartBeatThread: THeartBeatThread;
     FServerIncomingHeartBeats: Int64;
     FServerOutgoingHeartBeats: Int64;
@@ -122,7 +130,7 @@   TStompClient = class(TInterfacedObject, IStompClient)
     function ServerSupportsHeartBeat: boolean;
     procedure OnHeartBeatErrorHandler(Sender: TObject);
     procedure DoHeartBeatErrorHandler;
-    procedure OpenSSLGetPassword(var Password: String);
+    procedure OpenSSLGetPassword(var Password: IIdString);
   public
     Function SetUseSSL(const boUseSSL: boolean;
       const KeyFile : string =''; const CertFile : string = '';
@@ -197,36 +205,33 @@   TStompClient = class(TInterfacedObject, IStompClient)
   THeartBeatThread = class(TThread)
   private
     FStompClient: TStompClient;
-    FLock: TObject;
+    FLock: TCriticalSection;
     FOutgoingHeatBeatTimeout: Int64;
     FOnHeartBeatError: TNotifyEvent;
   protected
     procedure Execute; override;
     procedure DoHeartBeatError;
   public
-    constructor Create(StompClient: TStompClient; Lock: TObject;
+    constructor Create(StompClient: TStompClient; Lock: TCriticalSection;
       OutgoingHeatBeatTimeout: Int64); virtual;
     property OnHeartBeatError: TNotifyEvent read FOnHeartBeatError write FOnHeartBeatError;
   end;
 
 implementation
 
-{$IFDEF FPC}
-
-
-const
-  CHAR0 = #0;
-
-{$ELSE}
-
-
 uses
-  // Windows,   // Remove windows unit for compiling on ios
+{$IFDEF USESYNAPSE}
+  synautil;
+{$ELSE}
   IdGlobal,
-  IdGlobalProtocols,
-  Character, Winapi.Windows;
+  IdGlobalProtocols;
+{$ENDIF}
 
+{$IFDEF USESYNAPSE}
+const
+  CHAR0 = #0;
 {$ENDIF}
+
 { TStompClient }
 
 procedure TStompClient.AbortTransaction(const TransactionIdentifier: string);
@@ -356,7 +361,11 @@ procedure TStompClient.Connect(Host: string; Port: Integer; ClientID: string;
       FIOHandlerSocketOpenSSL.OnGetPassword := OpenSSLGetPassword;
       FIOHandlerSocketOpenSSL.Port := 0  ;
       FIOHandlerSocketOpenSSL.DefaultPort := 0       ;
+{$IF CompilerVersion < 24}
+      FIOHandlerSocketOpenSSL.SSLOptions.Method := sslvTLSv1; //sslvTLSv1_2; //sslvSSLv3; //sslvSSLv23;
+{$ELSE}
       FIOHandlerSocketOpenSSL.SSLOptions.Method := sslvTLSv1_2; //sslvSSLv3; //sslvSSLv23;
+{$IFEND}
       FIOHandlerSocketOpenSSL.SSLOptions.KeyFile  := FsslKeyFile;
       FIOHandlerSocketOpenSSL.SSLOptions.CertFile := FsslCertFile;
       FIOHandlerSocketOpenSSL.SSLOptions.Mode := sslmUnassigned; //sslmClient;
@@ -454,7 +463,7 @@ class function TStompClient.CreateAndConnect(Host: string; Port: Integer;
 constructor TStompClient.Create;
 begin
   inherited;
-  FLock := TObject.Create;
+  FLock := TCriticalSection.Create;
   FInTransaction := False;
   FSession := '';
   FUserName := 'guest';
@@ -638,9 +647,9 @@ procedure TStompClient.OnHeartBeatErrorHandler(Sender: TObject);
   DoHeartBeatErrorHandler;
 end;
 
-procedure TStompClient.OpenSSLGetPassword(var Password: String);
+procedure TStompClient.OpenSSLGetPassword(var Password: IIdString);
 begin
-  Password := FsslKeyPass;
+  Password := IIdString(FsslKeyPass);
 end;
 
 procedure TStompClient.ParseHeartBeat(Headers: IStompHeaders);
@@ -752,14 +761,14 @@ function TStompClient.Receive(ATimeout: Integer): IStompFrame;
     FreeEncoding: boolean;
 {$ELSE}
     Encoding: IIdTextEncoding;
-{$ENDIF}
+{$IFEND}
   begin
     Result := nil;
     lSBuilder := TStringBuilder.Create(1024 * 4);
     try
       FTCP.Socket.ReadTimeout := ATimeout;
       FTCP.Socket.DefStringEncoding :=
-{$IF CompilerVersion < 24}TIdTextEncoding.UTF8{$ELSE}IndyTextEncoding_UTF8{$ENDIF};
+{$IF CompilerVersion < 24}TIdTextEncoding.UTF8{$ELSE}IndyTextEncoding_UTF8{$IFEND};
 
       try
         lTimestampFirstReadLn := Now;
@@ -816,19 +825,21 @@ function TStompClient.Receive(ATimeout: Integer): IStompFrame;
             Encoding := CharsetToEncoding(Charset);
 {$IF CompilerVersion < 24}
             FreeEncoding := True;
-{$ENDIF}
+{$IFEND}
           end
           else
           begin
-            Encoding := IndyTextEncoding_8Bit();
 {$IF CompilerVersion < 24}
+            Encoding := Indy8BitEncoding();
             FreeEncoding := False;
-{$ENDIF}
+{$ELSE}
+            Encoding := IndyTextEncoding_8Bit();
+{$IFEND}
           end;
 
 {$IF CompilerVersion < 24}
           try
-{$ENDIF}
+{$IFEND}
             if Headers.IndexOfName('content-length') <> -1 then
             begin
               // length specified, read exactly that many bytes
@@ -855,7 +866,7 @@ function TStompClient.Receive(ATimeout: Integer): IStompFrame;
             if FreeEncoding then
               Encoding.Free;
           end;
-{$ENDIF}
+{$IFEND}
         finally
           Headers.Free;
         end;
@@ -925,7 +936,7 @@ procedure TStompClient.Send(QueueOrTopicName: string; TextMessage: string;
 
 procedure TStompClient.SendFrame(AFrame: IStompFrame);
 begin
-  TMonitor.Enter(FLock);
+  FLock.Enter;
   Try
     if Connected then // Test if error on Socket
     begin
@@ -952,13 +963,13 @@ procedure TStompClient.SendFrame(AFrame: IStompFrame);
       {$ENDIF}
     end;
   Finally
-    TMonitor.Exit(FLock);
+    FLock.Leave;
   End;
 end;
 
 procedure TStompClient.SendHeartBeat;
 begin
-  TMonitor.Enter(FLock);
+  FLock.Enter;
   Try
     if Connected then
     begin
@@ -977,7 +988,7 @@ procedure TStompClient.SendHeartBeat;
     {$ENDIF}
     end;
   Finally
-    TMonitor.Exit(FLock);
+    FLock.Leave;
   End;
 end;
 
@@ -1073,7 +1084,7 @@ procedure TStompClient.Unsubscribe(Queue: string; const subscriptionId: string =
 
 { THeartBeatThread }
 
-constructor THeartBeatThread.Create(StompClient: TStompClient; Lock: TObject;
+constructor THeartBeatThread.Create(StompClient: TStompClient; Lock: TCriticalSection;
   OutgoingHeatBeatTimeout: Int64);
 begin
   inherited Create(True);
diff --git a/StompTypes.pas b/StompTypes.pas
index a24e55e..bc9ff11 100644
--- a/StompTypes.pas
+++ b/StompTypes.pas
@@ -247,6 +247,11 @@   TReceiverThread = class(TThread)
   private
     FStompClient: IStompClient;
     FStompClientListener: IStompClientListener;
+    FReceiveFrame: IStompFrame;
+    FTerminateListener: Boolean;
+  private
+    procedure DoListenerMessage;
+    procedure DoListenerStopped;
   protected
     procedure Execute; override;
   public
@@ -660,28 +665,27 @@ constructor TReceiverThread.Create(StompClient: IStompClient;
   FStompClientListener := StompClientListener;
 end;
 
+procedure TReceiverThread.DoListenerMessage;
+begin
+  FStompClientListener.OnMessage(FReceiveFrame, FTerminateListener);
+end;
+
+procedure TReceiverThread.DoListenerStopped;
+begin
+  FStompClientListener.OnListenerStopped(FStompClient);
+end;
+
 procedure TReceiverThread.Execute;
-var
-  LFrame: IStompFrame;
-  LTerminateListener: Boolean;
 begin
-  LTerminateListener := False;
-  while (not Terminated) and (not LTerminateListener) do
+  FTerminateListener := False;
+  while (not Terminated) and (not FTerminateListener) do
   begin
-    if FStompClient.Receive(LFrame, 1000) then
+    if FStompClient.Receive(FReceiveFrame, 1000) then
     begin
-      TThread.Synchronize(nil,
-        procedure
-        begin
-          FStompClientListener.OnMessage(LFrame, LTerminateListener);
-        end);
+      TThread.Synchronize(nil, DoListenerMessage);
     end;
   end;
-  TThread.Synchronize(nil,
-    procedure
-    begin
-      FStompClientListener.OnListenerStopped(FStompClient);
-    end);
+  TThread.Synchronize(nil, DoListenerStopped);
 end;
 
 end.