- safe callbacks, ISocketContext interface is used everywhere internally

- sync emit
- error + cleanup on disconnect

IdHTTPWebsocketClient.pas

@@ -504,7 +504,9 @@ var
 begin
   Lock;
   try
-    if not IOHandler.IsWebsocket then
+    if IOHandler = nil then
+      Connect
+    else if not IOHandler.IsWebsocket then
       InternalUpgradeToWebsocket(True{raise}, sError);
   finally
     UnLock;

IdServerSocketIOHandling.pas

@@ -11,14 +11,14 @@ uses
 type
   TIdServerSocketIOHandling = class(TIdBaseSocketIOHandling)
   protected
-    procedure ProcessHeatbeatRequest(const AContext: TSocketIOContext; const aText: string); override;
+    procedure ProcessHeatbeatRequest(const AContext: ISocketIOContext; const aText: string); override;
   public
     function  SendToAll(const aMessage: string; const aCallback: TSocketIOMsgJSON = nil; const aOnError: TSocketIOError = nil): Integer;
     procedure SendTo   (const aContext: TIdServerContext; const aMessage: string; const aCallback: TSocketIOMsgJSON = nil; const aOnError: TSocketIOError = nil);
 
     function  EmitEventToAll(const aEventName: string; const aData: ISuperObject; const aCallback: TSocketIOMsgJSON = nil; const aOnError: TSocketIOError = nil): Integer;overload;
     function  EmitEventToAll(const aEventName: string; const aData: string      ; const aCallback: TSocketIOMsgJSON = nil; const aOnError: TSocketIOError = nil): Integer;overload;
-    procedure EmitEventTo   (const aContext: TSocketIOContext;
+    procedure EmitEventTo   (const aContext: ISocketIOContext;
                              const aEventName: string; const aData: ISuperObject; const aCallback: TSocketIOMsgJSON = nil; const aOnError: TSocketIOError = nil);overload;
     procedure EmitEventTo   (const aContext: TIdServerContext;
                              const aEventName: string; const aData: ISuperObject; const aCallback: TSocketIOMsgJSON = nil; const aOnError: TSocketIOError = nil);overload;
@@ -32,7 +32,7 @@ uses
 { TIdServerSocketIOHandling }
 
 procedure TIdServerSocketIOHandling.EmitEventTo(
-  const aContext: TSocketIOContext; const aEventName: string;
+  const aContext: ISocketIOContext; const aEventName: string;
   const aData: ISuperObject; const aCallback: TSocketIOMsgJSON; const aOnError: TSocketIOError);
 var
   jsonarray: string;
@@ -61,7 +61,7 @@ procedure TIdServerSocketIOHandling.EmitEventTo(
   const aContext: TIdServerContext; const aEventName: string;
   const aData: ISuperObject; const aCallback: TSocketIOMsgJSON; const aOnError: TSocketIOError);
 var
-  context: TSocketIOContext;
+  context: ISocketIOContext;
 begin
   Lock;
   try
@@ -76,7 +76,7 @@ function TIdServerSocketIOHandling.EmitEventToAll(const aEventName,
   aData: string; const aCallback: TSocketIOMsgJSON;
   const aOnError: TSocketIOError): Integer;
 var
-  context: TSocketIOContext;
+  context: ISocketIOContext;
   jsonarray: string;
 begin
   Result := 0;
@@ -127,7 +127,7 @@ begin
 end;
 
 procedure TIdServerSocketIOHandling.ProcessHeatbeatRequest(
-  const AContext: TSocketIOContext; const aText: string);
+  const AContext: ISocketIOContext; const aText: string);
 begin
   inherited ProcessHeatbeatRequest(AContext, aText);
 end;
@@ -135,7 +135,7 @@ end;
 procedure TIdServerSocketIOHandling.SendTo(const aContext: TIdServerContext;
   const aMessage: string; const aCallback: TSocketIOMsgJSON; const aOnError: TSocketIOError);
 var
-  context: TSocketIOContext;
+  context: ISocketIOContext;
 begin
   Lock;
   try
@@ -159,7 +159,7 @@ end;
 function TIdServerSocketIOHandling.SendToAll(const aMessage: string;
   const aCallback: TSocketIOMsgJSON; const aOnError: TSocketIOError): Integer;
 var
-  context: TSocketIOContext;
+  context: ISocketIOContext;
 begin
   Result := 0;
   Lock;

IdSocketIOHandling.pas

@@ -31,8 +31,8 @@ type
 
   ISocketIOContext = interface
     ['{ACCAC678-054C-4D75-8BAD-5922F55623AB}']
-    function GetCustomData: TObject;
+    function  GetCustomData: TObject;
-    function GetOwnsCustomData: Boolean;
+    function  GetOwnsCustomData: Boolean;
     procedure SetCustomData(const Value: TObject);
     procedure SetOwnsCustomData(const Value: Boolean);
 
@@ -43,6 +43,11 @@ type
     function PeerIP: string;
     function PeerPort: Integer;
 
+    procedure Lock;
+    procedure UnLock;
+
+    function IsDisconnected: Boolean;
+
     procedure EmitEvent(const aEventName: string; const aData: ISuperObject; const aCallback: TSocketIOMsgJSON = nil; const aOnError: TSocketIOError = nil);overload;
     procedure EmitEvent(const aEventName: string; const aData: string; const aCallback: TSocketIOMsgJSON = nil; const aOnError: TSocketIOError = nil);overload;
     procedure Send(const aData: string; const aCallback: TSocketIOMsgJSON = nil; const aOnError: TSocketIOError = nil);
@@ -73,6 +78,7 @@ type
     FClient: TIdHTTP;
     FEvent: TEvent;
     FQueue: TList<string>;
+    FPendingMessages: TList<Int64>;
     procedure QueueData(const aData: string);
     procedure ServerContextDestroy(AContext: TIdContext);
   public
@@ -118,20 +124,35 @@ type
                                ISocketIOCallback)
   protected
     FHandling: TIdBaseSocketIOHandling;
-    FSocket: TSocketIOContext;
+    FSocket: ISocketIOContext;
     FMsgNr: Integer;
     {ISocketIOCallback}
     procedure SendResponse(const aResponse: string);
     function  IsResponseSend: Boolean;
   public
-    constructor Create(aHandling: TIdBaseSocketIOHandling; aSocket: TSocketIOContext; aMsgNr: Integer);
+    constructor Create(aHandling: TIdBaseSocketIOHandling; aSocket: ISocketIOContext; aMsgNr: Integer);
   end;
 
+  TSocketIOPromise = class
+  protected
+    Done, Success: Boolean;
+    Error: Exception;
+    Data : ISuperObject;
+    Event: TEvent;
+  public
+    procedure  AfterConstruction; override;
+    destructor Destroy; override;
+  end;
+
+  ESocketIOException  = class(Exception);
+  ESocketIOTimeout    = class(ESocketIOException);
+  ESocketIODisconnect = class(ESocketIOException);
+
   TIdBaseSocketIOHandling = class(TIdServerBaseHandling)
   protected
     FLock: TCriticalSection;
-    FConnections: TObjectDictionary<TIdContext,TSocketIOContext>;
+    FConnections: TObjectDictionary<TIdContext,ISocketIOContext>;
-    FConnectionsGUID: TObjectDictionary<string,TSocketIOContext>;
+    FConnectionsGUID: TObjectDictionary<string,ISocketIOContext>;
 
     FOnConnectionList,
     FOnDisconnectList: TSocketIONotifyList;
@@ -139,7 +160,7 @@ type
     FOnSocketIOMsg: TSocketIOMsg;
     FOnSocketIOJson: TSocketIOMsgJSON;
 
-    procedure ProcessEvent(const AContext: TSocketIOContext; const aText: string; aMsgNr: Integer; aHasCallback: Boolean);
+    procedure ProcessEvent(const AContext: ISocketIOContext; const aText: string; aMsgNr: Integer; aHasCallback: Boolean);
   private
     FOnEventError: TSocketIOEventError;
   protected
@@ -150,21 +171,23 @@ type
       FSocketIOMsgNr: Integer;
       FSocketIOEventCallback: TDictionary<Integer,TSocketIOCallback>;
       FSocketIOEventCallbackRef: TDictionary<Integer,TSocketIOCallbackRef>;
+      //FSocketIOEventPromises: TDictionary<Integer,TSocketIOPromise>;
       FSocketIOErrorRef: TDictionary<Integer,TSocketIOError>;
 
-    function  WriteConnect(const ASocket: TSocketIOContext): string; overload;
+    function  WriteConnect(const ASocket: ISocketIOContext): string; overload;
-    procedure WriteDisConnect(const ASocket: TSocketIOContext);overload;
+    procedure WriteDisConnect(const ASocket: ISocketIOContext);overload;
-    procedure WritePing(const ASocket: TSocketIOContext);overload;
+    procedure WritePing(const ASocket: ISocketIOContext);overload;
     //
     function  WriteConnect(const AContext: TIdContext): string; overload;
     procedure WriteDisConnect(const AContext: TIdContext);overload;
     procedure WritePing(const AContext: TIdContext);overload;
 
-    procedure WriteSocketIOMsg(const ASocket: TSocketIOContext; const aRoom, aData: string; aCallback: TSocketIOCallbackRef = nil; const aOnError: TSocketIOError = nil);
+    procedure WriteSocketIOMsg(const ASocket: ISocketIOContext; const aRoom, aData: string; aCallback: TSocketIOCallbackRef = nil; const aOnError: TSocketIOError = nil);
-    procedure WriteSocketIOJSON(const ASocket: TSocketIOContext; const aRoom, aJSON: string; aCallback: TSocketIOCallbackRef = nil; const aOnError: TSocketIOError = nil);
+    procedure WriteSocketIOJSON(const ASocket: ISocketIOContext; const aRoom, aJSON: string; aCallback: TSocketIOCallbackRef = nil; const aOnError: TSocketIOError = nil);
-    procedure WriteSocketIOEvent(const ASocket: TSocketIOContext; const aRoom, aEventName, aJSONArray: string; aCallback: TSocketIOCallback; const aOnError: TSocketIOError);
+    procedure WriteSocketIOEvent(const ASocket: ISocketIOContext; const aRoom, aEventName, aJSONArray: string; aCallback: TSocketIOCallback; const aOnError: TSocketIOError);
-    procedure WriteSocketIOEventRef(const ASocket: TSocketIOContext; const aRoom, aEventName, aJSONArray: string; aCallback: TSocketIOCallbackRef; const aOnError: TSocketIOError);
+    procedure WriteSocketIOEventRef(const ASocket: ISocketIOContext; const aRoom, aEventName, aJSONArray: string; aCallback: TSocketIOCallbackRef; const aOnError: TSocketIOError);
-    procedure WriteSocketIOResult(const ASocket: TSocketIOContext; aRequestMsgNr: Integer; const aRoom, aData: string);
+    function  WriteSocketIOEventSync(const ASocket: ISocketIOContext; const aRoom, aEventName, aJSONArray: string; aMaxwait_ms: Integer = INFINITE): ISuperObject;
+    procedure WriteSocketIOResult(const ASocket: ISocketIOContext; aRequestMsgNr: Integer; const aRoom, aData: string);
 
     procedure ProcessSocketIO_XHR(const aGUID: string; const aStrmRequest, aStrmResponse: TStream);
 
@@ -172,9 +195,9 @@ type
     procedure ProcessSocketIORequest(const ASocket: ISocketIOContext; const aData: string);overload;
     procedure ProcessSocketIORequest(const AContext: TIdContext; const strmRequest: TMemoryStream);overload;
 
-    procedure ProcessHeatbeatRequest(const ASocket: TSocketIOContext; const aText: string);virtual;
+    procedure ProcessHeatbeatRequest(const ASocket: ISocketIOContext; const aText: string);virtual;
-    procedure ProcessCloseChannel(const ASocket: TSocketIOContext; const aChannel: string);virtual;
+    procedure ProcessCloseChannel(const ASocket: ISocketIOContext; const aChannel: string);virtual;
-    function  WriteString(const ASocket: TSocketIOContext; const aText: string): string; virtual;
+    function  WriteString(const ASocket: ISocketIOContext; const aText: string): string; virtual;
   public
     procedure  AfterConstruction; override;
     destructor Destroy; override;
@@ -186,10 +209,10 @@ type
     function  GetSocketIOContext(const AContext: TIdContext): ISocketIOContext;
 
 //    procedure  EmitEventToAll(const aEventName: string; const aData: ISuperObject; const aCallback: TSocketIOMsgJSON = nil);
-    function  NewConnection(const AContext: TIdContext): TSocketIOContext;overload;
+    function  NewConnection(const AContext: TIdContext): ISocketIOContext;overload;
-    function  NewConnection(const aGUID, aPeerIP: string): TSocketIOContext;overload;
+    function  NewConnection(const aGUID, aPeerIP: string): ISocketIOContext;overload;
     procedure FreeConnection(const AContext: TIdContext);overload;
-    procedure FreeConnection(const ASocket: TSocketIOContext);overload;
+    procedure FreeConnection(const ASocket: ISocketIOContext);overload;
 
     property  OnSocketIOMsg  : TSocketIOMsg read FOnSocketIOMsg  write FOnSocketIOMsg;
     property  OnSocketIOJson : TSocketIOMsgJSON read FOnSocketIOJson write FOnSocketIOJson;
@@ -206,6 +229,7 @@ type
   public
     procedure Send(const aMessage: string; const aCallback: TSocketIOMsgJSON = nil; const aOnError: TSocketIOError = nil);
     procedure Emit(const aEventName: string; const aData: ISuperObject; const aCallback: TSocketIOMsgJSON = nil; const aOnError: TSocketIOError = nil);overload;
+    function  EmitSync(const aEventName: string; const aData: ISuperObject; aMaxwait_ms: Integer = INFINITE): ISuperobject;
     //procedure Emit(const aEventName: string; const aData: string; const aCallback: TSocketIOMsgJSON = nil; const aOnError: TSocketIOError = nil);overload;
   end;
 
@@ -219,8 +243,8 @@ begin
   inherited;
   FLock := TCriticalSection.Create;
 
-  FConnections      := TObjectDictionary<TIdContext,TSocketIOContext>.Create([doOwnsValues]);
+  FConnections      := TObjectDictionary<TIdContext,ISocketIOContext>.Create([]);
-  FConnectionsGUID  := TObjectDictionary<string,TSocketIOContext>.Create([doOwnsValues]);
+  FConnectionsGUID  := TObjectDictionary<string,ISocketIOContext>.Create([]);
 
   FOnConnectionList := TSocketIONotifyList.Create;
   FOnDisconnectList := TSocketIONotifyList.Create;
@@ -229,11 +253,12 @@ begin
   FSocketIOEventCallback     := TDictionary<Integer,TSocketIOCallback>.Create;
   FSocketIOEventCallbackRef  := TDictionary<Integer,TSocketIOCallbackRef>.Create;
   FSocketIOErrorRef          := TDictionary<Integer,TSocketIOError>.Create;
+  //FSocketIOEventPromises     := TDictionary<Integer,TSocketIOPromise>.Create;
 end;
 
 function TIdBaseSocketIOHandling.ConnectionCount: Integer;
 var
-  context: TSocketIOContext;
+  context: ISocketIOContext;
 begin
   Lock;
   try
@@ -263,6 +288,7 @@ begin
   FSocketIOEventCallback.Free;
   FSocketIOEventCallbackRef.Free;
   FSocketIOErrorRef.Free;
+  //FSocketIOEventPromises.Free;
 
   FOnEventList.Free;
   FOnConnectionList.Free;
@@ -271,13 +297,13 @@ begin
   while FConnections.Count > 0 do
     for idcontext in FConnections.Keys do
     begin
-      FConnections.Items[idcontext]._Release;
+      //FConnections.Items[idcontext]._Release;
       FConnections.ExtractPair(idcontext);
     end;
   while FConnectionsGUID.Count > 0 do
     for squid in FConnectionsGUID.Keys do
     begin
-      FConnectionsGUID.Items[squid]._Release;
+      //FConnectionsGUID.Items[squid]._Release;
       FConnectionsGUID.ExtractPair(squid);
     end;
   FConnections.Free;
@@ -291,7 +317,7 @@ end;
 
 procedure TIdBaseSocketIOHandling.EnumerateSockets(
   const aEachSocketCallback: TSocketIONotify);
-var socket: TSocketIOContext;
+var socket: ISocketIOContext;
 begin
   Assert(Assigned(aEachSocketCallback));
   Lock;
@@ -314,26 +340,31 @@ begin
 end;
 
 procedure TIdBaseSocketIOHandling.FreeConnection(
-  const ASocket: TSocketIOContext);
+  const ASocket: ISocketIOContext);
 var squid: string;
     idcontext: TIdContext;
+    errorref: TSocketIOError;
+    i: Integer;
 begin
   if ASocket = nil then Exit;
   Lock;
   try
-    ASocket.Context    := nil;
+    with TSocketIOContext(ASocket) do
-    ASocket.FIOHandler := nil;
+    begin
-    ASocket.FClient    := nil;
+      Context    := nil;
-    ASocket.FHandling  := nil;
+      FIOHandler := nil;
-    ASocket.FGUID      := '';
+      FClient    := nil;
-    ASocket.FPeerIP    := '';
+      FHandling  := nil;
+      FGUID      := '';
+      FPeerIP    := '';
+    end;
 
     for idcontext in FConnections.Keys do
     begin
       if FConnections.Items[idcontext] = ASocket then
       begin
         FConnections.ExtractPair(idcontext);
-        ASocket._Release;
+        //ASocket._Release;
       end;
     end;
     for squid in FConnectionsGUID.Keys do
@@ -341,7 +372,22 @@ begin
       if FConnectionsGUID.Items[squid] = ASocket then
       begin
         FConnectionsGUID.ExtractPair(squid);
-        ASocket._Release; //use reference count? otherwise AV when used in TThread.Queue
+        //ASocket._Release; //use reference count? otherwise AV when used in TThread.Queue
+      end;
+    end;
+
+    //pending callbacks? then exceute error messages
+    for i in TSocketIOContext(ASocket).FPendingMessages do
+    begin
+      FSocketIOEventCallback.Remove(i);
+      FSocketIOEventCallbackRef.Remove(i);
+      if FSocketIOErrorRef.TryGetValue(i, errorref) then
+      begin
+        FSocketIOErrorRef.Remove(i);
+        try
+          errorref(ASocket, ESocketIODisconnect.ClassName, 'Connection disconnected');
+        except
+        end;
       end;
     end;
   finally
@@ -351,7 +397,7 @@ end;
 
 function TIdBaseSocketIOHandling.GetSocketIOContext(const AContext: TIdContext): ISocketIOContext;
 var
-  socket: TSocketIOContext;
+  socket: ISocketIOContext;
 begin
   Result := nil;
   Lock;
@@ -365,7 +411,7 @@ end;
 
 procedure TIdBaseSocketIOHandling.FreeConnection(const AContext: TIdContext);
 var
-  socket: TSocketIOContext;
+  socket: ISocketIOContext;
 begin
   Lock;
   try
@@ -384,18 +430,20 @@ begin
 end;
 
 function TIdBaseSocketIOHandling.NewConnection(
-  const AGUID, aPeerIP: string): TSocketIOContext;
+  const AGUID, aPeerIP: string): ISocketIOContext;
 var
   socket: TSocketIOContext;
 begin
   Lock;
   try
-    if not FConnectionsGUID.TryGetValue(AGUID, socket) then
+    if not FConnectionsGUID.TryGetValue(AGUID, Result) then
     begin
       socket := TSocketIOContext.Create;
-      socket._AddRef;
       FConnectionsGUID.Add(AGUID, socket);
-    end;
+    end
+    else
+      socket := TSocketIOContext(Result);
+
     //socket.Context      := AContext;
     socket.FGUID        := AGUID;
     if aPeerIP <> '' then
@@ -409,18 +457,20 @@ begin
   end;
 end;
 
-function TIdBaseSocketIOHandling.NewConnection(const AContext: TIdContext): TSocketIOContext;
+function TIdBaseSocketIOHandling.NewConnection(const AContext: TIdContext): ISocketIOContext;
 var
   socket: TSocketIOContext;
 begin
   Lock;
   try
-    if not FConnections.TryGetValue(AContext, socket) then
+    if not FConnections.TryGetValue(AContext, Result) then
     begin
       socket := TSocketIOContext.Create;
-      socket._AddRef;
       FConnections.Add(AContext, socket);
-    end;
+    end
+    else
+      socket := TSocketIOContext(Result);
+
     socket.Context      := AContext;
     socket.FHandling    := Self;
     socket.FConnectSend := False;
@@ -432,7 +482,7 @@ begin
 end;
 
 procedure TIdBaseSocketIOHandling.OnConnection(const aCallback: TSocketIONotify);
-var context: TSocketIOContext;
+var context: ISocketIOContext;
 begin
   FOnConnectionList.Add(aCallback);
 
@@ -465,16 +515,16 @@ begin
 end;
 
 procedure TIdBaseSocketIOHandling.ProcessCloseChannel(
-  const ASocket: TSocketIOContext; const aChannel: string);
+  const ASocket: ISocketIOContext; const aChannel: string);
 begin
   if aChannel <> '' then
     //todo: close channel
-  else if (ASocket.FContext <> nil) then
+  else if (TSocketIOContext(ASocket).FContext <> nil) then
-    ASocket.FContext.Connection.Disconnect;
+    TSocketIOContext(ASocket).FContext.Connection.Disconnect;
 end;
 
 procedure TIdBaseSocketIOHandling.ProcessEvent(
-  const AContext: TSocketIOContext; const aText: string; aMsgNr: Integer;
+  const AContext: ISocketIOContext; const aText: string; aMsgNr: Integer;
   aHasCallback: Boolean);
 var
   json: ISuperObject;
@@ -527,14 +577,17 @@ begin
   end;
 end;
 
-procedure TIdBaseSocketIOHandling.ProcessHeatbeatRequest(const ASocket: TSocketIOContext; const aText: string);
+procedure TIdBaseSocketIOHandling.ProcessHeatbeatRequest(const ASocket: ISocketIOContext; const aText: string);
 begin
-  if ASocket.PingSend then
+  with TSocketIOContext(ASocket) do
-    ASocket.PingSend := False   //reset, client responded with 2:: heartbeat too
-  else
   begin
-    ASocket.PingSend := True;  //stop infinite ping response loops
+    if PingSend then
-    WriteString(ASocket, aText);   //write same connect back, e.g. 2::
+      PingSend := False   //reset, client responded with 2:: heartbeat too
+    else
+    begin
+      PingSend := True;  //stop infinite ping response loops
+      WriteString(ASocket, aText);   //write same connect back, e.g. 2::
+    end;
   end;
 end;
 
@@ -562,7 +615,7 @@ end;
 procedure TIdBaseSocketIOHandling.ProcessSocketIORequest(const AContext: TIdContext;
   const strmRequest: TMemoryStream);
 var
-  socket: TSocketIOContext;
+  socket: ISocketIOContext;
 begin
   if not FConnections.TryGetValue(AContext, socket) then
   begin
@@ -574,7 +627,7 @@ end;
 procedure TIdBaseSocketIOHandling.ProcessSocketIO_XHR(const aGUID: string; // const AContext: TIdContext;
   const aStrmRequest, aStrmResponse: TStream);
 var
-  socket: TSocketIOContext;
+  socket: ISocketIOContext;
   sdata: string;
   i, ilength: Integer;
   bytes, singlemsg: TBytes;
@@ -584,7 +637,7 @@ begin
   then
     socket := NewConnection(aGUID, '');
 
-  if not socket.FConnectSend then
+  if not TSocketIOContext(socket).FConnectSend then
     WriteConnect(socket);
 
   if (aStrmRequest <> nil) and
@@ -633,12 +686,12 @@ begin
   if aStrmResponse = nil then Exit;  
 
   //wait till some response data to be send (long polling)
-  sdata := socket.WaitForQueue(5 * 1000);
+  sdata := TSocketIOContext(socket).WaitForQueue(5 * 1000);
   if sdata = '' then
   begin
     //no data? then send ping
     WritePing(socket);
-    sdata := socket.WaitForQueue(0);
+    sdata := TSocketIOContext(socket).WaitForQueue(0);
   end;
   //send response back
   if sdata <> '' then
@@ -835,6 +888,7 @@ begin
     imsg  := StrToIntDef(smsg, 0);
     sData := Copy(sdata, Pos('+', sData)+1, Length(sData));
 
+    TSocketIOContext(ASocket).FPendingMessages.Remove(imsg);
     if FSocketIOErrorRef.TryGetValue(imsg, errorref) then
     begin
       FSocketIOErrorRef.Remove(imsg);
@@ -849,6 +903,9 @@ begin
           errorref(ASocket, error.S['Type'], error.S['Message'])
         else
           errorref(ASocket, 'Unknown', sdata);
+
+        FSocketIOEventCallback.Remove(imsg);
+        FSocketIOEventCallbackRef.Remove(imsg);
         Exit;
       end;
     end;
@@ -881,7 +938,7 @@ begin
 end;
 
 function TIdBaseSocketIOHandling.WriteConnect(
-  const ASocket: TSocketIOContext): string;
+  const ASocket: ISocketIOContext): string;
 var
   notify: TSocketIONotify;
 begin
@@ -894,9 +951,9 @@ begin
       FConnections.Add(nil, ASocket);  //clients do not have a TIdContext?
     end;
 
-    if not ASocket.ConnectSend then
+    if not TSocketIOContext(ASocket).ConnectSend then
     begin
-      ASocket.ConnectSend := True;
+      TSocketIOContext(ASocket).ConnectSend := True;
       Result := WriteString(ASocket, '1::');
     end;
   finally
@@ -908,7 +965,7 @@ begin
 end;
 
 procedure TIdBaseSocketIOHandling.WriteDisConnect(
-  const ASocket: TSocketIOContext);
+  const ASocket: ISocketIOContext);
 var
   notify: TSocketIONotify;
 begin
@@ -930,13 +987,13 @@ begin
 end;
 
 procedure TIdBaseSocketIOHandling.WritePing(
-  const ASocket: TSocketIOContext);
+  const ASocket: ISocketIOContext);
 begin
-  ASocket.PingSend := True;
+  TSocketIOContext(ASocket).PingSend := True;
   WriteString(ASocket, '2::')   //heartbeat: https://github.com/LearnBoost/socket.io-spec
 end;
 
-procedure TIdBaseSocketIOHandling.WriteSocketIOEvent(const ASocket: TSocketIOContext; const aRoom, aEventName,
+procedure TIdBaseSocketIOHandling.WriteSocketIOEvent(const ASocket: ISocketIOContext; const aRoom, aEventName,
   aJSONArray: string; aCallback: TSocketIOCallback; const aOnError: TSocketIOError);
 var
   sresult: string;
@@ -950,11 +1007,12 @@ begin
                       [inr, aRoom, aEventName, aJSONArray])
   else
   begin
-    if FSocketIOEventCallback = nil then
+    //if FSocketIOEventCallback = nil then
-      FSocketIOEventCallback := TDictionary<Integer,TSocketIOCallback>.Create;
+    //  FSocketIOEventCallback := TDictionary<Integer,TSocketIOCallback>.Create;
     sresult := Format('5:%d+:%s:{"name":"%s", "args":%s}',
                       [inr, aRoom, aEventName, aJSONArray]);
     FSocketIOEventCallback.Add(inr, aCallback);
+    TSocketIOContext(ASocket).FPendingMessages.Add(inr);
 
     if Assigned(aOnError) then
       FSocketIOErrorRef.Add(inr, aOnError);
@@ -962,7 +1020,7 @@ begin
   WriteString(ASocket, sresult);
 end;
 
-procedure TIdBaseSocketIOHandling.WriteSocketIOEventRef(const ASocket: TSocketIOContext;
+procedure TIdBaseSocketIOHandling.WriteSocketIOEventRef(const ASocket: ISocketIOContext;
   const aRoom, aEventName, aJSONArray: string; aCallback: TSocketIOCallbackRef; const aOnError: TSocketIOError);
 var
   sresult: string;
@@ -976,11 +1034,12 @@ begin
                       [inr, aRoom, aEventName, aJSONArray])
   else
   begin
-    if FSocketIOEventCallbackRef = nil then
+    //if FSocketIOEventCallbackRef = nil then
-      FSocketIOEventCallbackRef := TDictionary<Integer,TSocketIOCallbackRef>.Create;
+    //  FSocketIOEventCallbackRef := TDictionary<Integer,TSocketIOCallbackRef>.Create;
     sresult := Format('5:%d+:%s:{"name":"%s", "args":%s}',
                       [inr, aRoom, aEventName, aJSONArray]);
     FSocketIOEventCallbackRef.Add(inr, aCallback);
+    TSocketIOContext(ASocket).FPendingMessages.Add(inr);
 
     if Assigned(aOnError) then
       FSocketIOErrorRef.Add(inr, aOnError);
@@ -988,7 +1047,92 @@ begin
   WriteString(ASocket, sresult);
 end;
 
-procedure TIdBaseSocketIOHandling.WriteSocketIOJSON(const ASocket: TSocketIOContext;
+function TIdBaseSocketIOHandling.WriteSocketIOEventSync(const ASocket: ISocketIOContext; const aRoom, aEventName,
+  aJSONArray: string; aMaxwait_ms: Integer = INFINITE): ISuperObject;
+var
+  sresult: string;
+  inr: Integer;
+  promise: TSocketIOPromise;
+begin
+  Result := nil;
+  if (ASocket = nil) or (ASocket.IsDisconnected) then
+    raise ESocketIOException.CreateFmt('Socket is not connected, cannot send "%s" request', [aEventName]);
+
+  //see TROIndyHTTPWebsocketServer.ProcessSocketIORequest too
+  //5:1+:/chat:{"name":"GetLocations","args":[""]}
+  inr := InterlockedIncrement(FSocketIOMsgNr);
+
+//  if FSocketIOEventPromises = nil then
+//    FSocketIOEventPromises := TDictionary<Integer,TSocketIOPromise>.Create;
+  promise := TSocketIOPromise.Create;
+//  FSocketIOEventPromises.Add(inr, promise);
+
+  sresult := Format('5:%d+:%s:{"name":"%s", "args":%s}',
+                    [inr, aRoom, aEventName, aJSONArray]);
+  Lock;
+  try
+    FSocketIOEventCallbackRef.Add(inr,
+      procedure(const aData: string)
+      begin
+        promise.Success := True;
+        promise.Error   := nil;
+        promise.Data    := SO(aData);
+        promise.Done    := True;
+        promise.Event.SetEvent;
+      end);
+    FSocketIOErrorRef.Add(inr,
+      procedure(const ASocket: ISocketIOContext; const aErrorClass, aErrorMessage: string)
+      begin
+        promise.Success := False;
+        promise.Error   := ESocketIOException.Create(aErrorClass + ': ' + aErrorMessage);
+        promise.Data    := nil;
+        promise.Done    := True;
+        promise.Event.SetEvent;
+      end);
+    TSocketIOContext(ASocket).FPendingMessages.Add(inr);
+  finally
+    Unlock;
+  end;
+
+  try
+    try
+      if ASocket.IsDisconnected then
+        raise ESocketIOException.CreateFmt('Socket is disconnected, cannot send "%s" request', [aEventName])
+      else
+        WriteString(ASocket, sresult);
+
+      //wait for callback
+      if promise.Event.WaitFor(aMaxwait_ms) = wrSignaled then
+        Assert(promise.Done)
+      else
+        //timeout
+        raise ESocketIOTimeout.CreateFmt('No response received for "%s" request', [aEventName]);
+    except
+      Lock;
+      try
+        FSocketIOEventCallbackRef.Remove(inr);
+        FSocketIOErrorRef.Remove(inr);
+        TSocketIOContext(ASocket).FPendingMessages.Remove(inr);
+      finally
+        UnLock;
+      end;
+      raise;
+    end;
+
+    Result := promise.Data;
+    if promise.Error <> nil then
+    begin
+      Assert(not promise.Success);
+      raise promise.Error;
+    end
+    else
+      Assert(promise.Success);
+  finally
+    promise.Free;
+  end;
+end;
+
+procedure TIdBaseSocketIOHandling.WriteSocketIOJSON(const ASocket: ISocketIOContext;
   const aRoom, aJSON: string; aCallback: TSocketIOCallbackRef = nil; const aOnError: TSocketIOError = nil);
 var
   sresult: string;
@@ -1002,11 +1146,12 @@ begin
     sresult := Format('4:%d:%s:%s', [inr, aRoom, aJSON])
   else
   begin
-    if FSocketIOEventCallbackRef = nil then
+    //if FSocketIOEventCallbackRef = nil then
-      FSocketIOEventCallbackRef := TDictionary<Integer,TSocketIOCallbackRef>.Create;
+    //  FSocketIOEventCallbackRef := TDictionary<Integer,TSocketIOCallbackRef>.Create;
     sresult := Format('4:%d+:%s:%s',
                       [inr, aRoom, aJSON]);
     FSocketIOEventCallbackRef.Add(inr, aCallback);
+    TSocketIOContext(ASocket).FPendingMessages.Add(inr);
 
     if Assigned(aOnError) then
       FSocketIOErrorRef.Add(inr, aOnError);
@@ -1015,7 +1160,7 @@ begin
   WriteString(ASocket, sresult);
 end;
 
-procedure TIdBaseSocketIOHandling.WriteSocketIOMsg(const ASocket: TSocketIOContext;
+procedure TIdBaseSocketIOHandling.WriteSocketIOMsg(const ASocket: ISocketIOContext;
   const aRoom, aData: string; aCallback: TSocketIOCallbackRef = nil; const aOnError: TSocketIOError = nil);
 var
   sresult: string;
@@ -1029,11 +1174,12 @@ begin
     sresult := Format('3:%d:%s:%s', [inr, aRoom, aData])
   else
   begin
-    if FSocketIOEventCallbackRef = nil then
+    //if FSocketIOEventCallbackRef = nil then
-      FSocketIOEventCallbackRef := TDictionary<Integer,TSocketIOCallbackRef>.Create;
+    //  FSocketIOEventCallbackRef := TDictionary<Integer,TSocketIOCallbackRef>.Create;
     sresult := Format('3:%d+:%s:%s',
                       [inr, aRoom, aData]);
     FSocketIOEventCallbackRef.Add(inr, aCallback);
+    TSocketIOContext(ASocket).FPendingMessages.Add(inr);
 
     if Assigned(aOnError) then
       FSocketIOErrorRef.Add(inr, aOnError);
@@ -1042,7 +1188,7 @@ begin
   WriteString(ASocket, sresult);
 end;
 
-procedure TIdBaseSocketIOHandling.WriteSocketIOResult(const ASocket: TSocketIOContext;
+procedure TIdBaseSocketIOHandling.WriteSocketIOResult(const ASocket: ISocketIOContext;
   aRequestMsgNr: Integer; const aRoom, aData: string);
 var
   sresult: string;
@@ -1052,33 +1198,36 @@ begin
   WriteString(ASocket, sresult);
 end;
 
-function TIdBaseSocketIOHandling.WriteString(const ASocket: TSocketIOContext;
+function TIdBaseSocketIOHandling.WriteString(const ASocket: ISocketIOContext;
   const aText: string): string;
 begin
   if ASocket = nil then Exit;
 
   ASocket.Lock;
   try
-    if ASocket.FIOHandler = nil then
+    with TSocketIOContext(ASocket) do
     begin
-      if ASocket.FContext <> nil then
+      if FIOHandler = nil then
-        ASocket.FIOHandler := (ASocket.FContext as TIdServerWSContext).IOHandler;
+      begin
-    end;
+        if FContext <> nil then
+          FIOHandler := (FContext as TIdServerWSContext).IOHandler;
+      end;
 
-    if (ASocket.FIOHandler <> nil) then
+      if (FIOHandler <> nil) then
-    begin
+      begin
-      //Assert(ASocket.FIOHandler.IsWebsocket);
+        //Assert(ASocket.FIOHandler.IsWebsocket);
-//      if DebugHook <> 0 then
+  //      if DebugHook <> 0 then
-//        Windows.OutputDebugString(PChar('Send: ' + aText));
+  //        Windows.OutputDebugString(PChar('Send: ' + aText));
-      ASocket.FIOHandler.Write(aText);
+        FIOHandler.Write(aText);
-    end
+      end
-    else if ASocket.GUID <> '' then
+      else if GUID <> '' then
-    begin
+      begin
-      ASocket.QueueData(aText);
+        QueueData(aText);
-      Result := aText;    //for xhr-polling the data must be send using responseinfo instead of direct write!
+        Result := aText;    //for xhr-polling the data must be send using responseinfo instead of direct write!
-    end
+      end;
-    else   //disconnected
+      //else   //disconnected
-      Assert(False, 'disconnected');
+      //  Assert(False, 'disconnected');
+    end;
   finally
     ASocket.UnLock;
   end;
@@ -1087,7 +1236,7 @@ end;
 { TSocketIOCallbackObj }
 
 constructor TSocketIOCallbackObj.Create(aHandling: TIdBaseSocketIOHandling;
-  aSocket: TSocketIOContext; aMsgNr: Integer);
+  aSocket: ISocketIOContext; aMsgNr: Integer);
 begin
   FHandling := aHandling;
   FSocket   := aSocket;
@@ -1113,6 +1262,7 @@ begin
   inherited;
   FLock  := TCriticalSection.Create;
   FQueue := TList<string>.Create;
+  FPendingMessages := TList<Int64>.Create;
 end;
 
 constructor TSocketIOContext.Create(aClient: TIdHTTP);
@@ -1134,6 +1284,7 @@ begin
   FLock.Free;
   if OwnsCustomData then
     FCustomData.Free;
+  FPendingMessages.Free;
   inherited;
 end;
 
@@ -1336,7 +1487,7 @@ end;
 
 function TIdBaseSocketIOHandling.WriteConnect(const AContext: TIdContext): string;
 var
-  socket: TSocketIOContext;
+  socket: ISocketIOContext;
 begin
   //if not FConnections.TryGetValue(AContext, socket) then
   socket := NewConnection(AContext);
@@ -1345,7 +1496,7 @@ end;
 
 procedure TIdBaseSocketIOHandling.WriteDisConnect(const AContext: TIdContext);
 var
-  socket: TSocketIOContext;
+  socket: ISocketIOContext;
 begin
   if not FConnections.TryGetValue(AContext, socket) then
     socket := NewConnection(AContext);
@@ -1354,7 +1505,7 @@ end;
 
 procedure TIdBaseSocketIOHandling.WritePing(const AContext: TIdContext);
 var
-  socket: TSocketIOContext;
+  socket: ISocketIOContext;
 begin
   if not FConnections.TryGetValue(AContext, socket) then
     socket := NewConnection(AContext);
@@ -1366,7 +1517,7 @@ end;
 procedure TIdSocketIOHandling.Emit(const aEventName: string;
   const aData: ISuperObject; const aCallback: TSocketIOMsgJSON; const aOnError: TSocketIOError);
 var
-  context: TSocketIOContext;
+  context: ISocketIOContext;
   jsonarray: string;
   isendcount: Integer;
 begin
@@ -1384,7 +1535,7 @@ begin
   try
     isendcount := 0;
 
-    //note: is single connection?
+    //note: client has single connection?
     for context in FConnections.Values do
     begin
       if context.IsDisconnected then Continue;
@@ -1421,10 +1572,53 @@ begin
   end;
 end;
 
+function TIdSocketIOHandling.EmitSync(const aEventName: string; const aData: ISuperObject; aMaxwait_ms: Integer = INFINITE): ISuperobject;
+var
+  firstcontext, context: ISocketIOContext;
+  jsonarray: string;
+  isendcount: Integer;
+begin
+  if aData <> nil then
+  begin
+    if aData.IsType(stArray) then
+      jsonarray := aData.AsString
+    else if aData.IsType(stString) then
+      jsonarray := '["' + aData.AsString + '"]'
+    else
+      jsonarray := '[' + aData.AsString + ']';
+  end;
+
+  Lock;
+  try
+    isendcount := 0;
+    //note: client has single connection?
+    for context in FConnections.Values do
+    begin
+      if context.IsDisconnected then Continue;
+      firstcontext := context;
+      Inc(isendcount);
+    end;
+    for context in FConnectionsGUID.Values do
+    begin
+      if context.IsDisconnected then Continue;
+      firstcontext := context;
+      Inc(isendcount);
+    end;
+
+    //todo: use multiple promises?
+    if isendcount > 1 then
+      raise EIdSocketIoUnhandledMessage.Create('Cannot emit synchronized to more than one connection!');
+  finally
+    UnLock;
+  end;
+
+  Result := WriteSocketIOEventSync(firstcontext, ''{no room}, aEventName, jsonarray, aMaxwait_ms);
+end;
+
 procedure TIdSocketIOHandling.Send(const aMessage: string;
   const aCallback: TSocketIOMsgJSON; const aOnError: TSocketIOError);
 var
-  context: TSocketIOContext;
+  context: ISocketIOContext;
   isendcount: Integer;
 begin
   Lock;
@@ -1468,4 +1662,18 @@ begin
   end;
 end;
 
+{ TSocketIOPromise }
+
+procedure TSocketIOPromise.AfterConstruction;
+begin
+  inherited;
+  Event := TEvent.Create();
+end;
+
+destructor TSocketIOPromise.Destroy;
+begin
+  Event.Free;
+  inherited;
+end;
+
 end.