Im writing an Indy chat app, and am wondering if there is a way for the server component to tell the client that there is a string waiting, or even a way for the client to have an "OnExecute" like event.
This is what i have now:
server:
procedure TServer.ServerExecute(AContext: TIdContext);
var
sResponse: string;
I: Integer;
list: Tlist;
begin
List := Server.Contexts.LockList;
sResponse:= AContext.Connection.Socket.ReadLn;
try
for I := 0 to List.Count-1 do
begin
try
TIdContext(List[I]).Connection.IOHandler.WriteLn(sResponse);
except
end;
end;
finally
Server.Contexts.UnlockList;
end;
end;
Client:
procedure TForm1.Button1Click(Sender: TObject);
var
sMsg : string;
begin
Client.Socket.WriteLn(edit1.Text);
sMsg := Client.Socket.ReadLn;
Memo1.Lines.Add(sMsg);
end;
The problem is when i have 2 or more clients running the messages keep stacking because the button only processes 1 message a time. I'd like a way for the client to wait for messages and when it is triggered it processes those messages, like it does now under the button procedure. I've tried to put the "readln" part under a timer, but that causes some major problems.
Im Using Delphi 2010 and Indy 10
procedure TForm1.Timer1Timer(Sender: TObject);
var
sMsg : string;
begin
IdIOHandlerStack1.CheckForDataOnSource(0);
sMsg := IdIOHandlerStack1.InputBuffer.AsString;
if not (sMsg = '') then
begin
Memo1.Lines.Add(IdIOHandlerStack1.InputBuffer.AsString);
IdIOHandlerStack1.InputBuffer.Clear;
end;
end;
Related
There's an overloaded version of the Execute function of the TDBXCallback calls in Data.DBXJSon that looks like this
function Execute(Arg: TObject): TObject; overload; virtual; abstract;
Which in my Datasnap client, I've implemented like this:
type
ServerChannelCallBack = class(TDBXCallback)
public
function Execute(const Arg: TJSONValue): TJSONValue; overload; override; // this works!
function Execute(Arg: TObject): TObject; overload; override; // this doesn't
end;
function ServerChannelCallBack.Execute(Arg: TObject): TObject;
var
i: Integer;
begin
Result := TObject.Create; // is this correct?
try
if Arg is TStringList then
begin
FormClient.QueueLogMsg('ServerChannel', 'Got TStringList');
for i := 0 to TStrings(Arg).Count - 1 do
FormClient.QueueLogMsg('ServerChannel', TStringList(Arg)[i]);
end;
finally
end;
end;
This is called from the Datasnap server like this:
procedure TFormServer.Button2Click(Sender: TObject);
var
sr: TStringList;
begin
sr := TStringList.Create;
try
sr.Add('one');
sr.Add('two');
ServerContainer2.DSServer1.BroadcastObject('SERVERCHANNEL', sr);
finally
// sr
end;
end;
This is following on from an example in the video presented by Matt DeLong
Heavyweight Callbacks with DataSnap - Part 1: Thick Client
The callback works perfectly, but only exactly once! On the second call from the server (Button2Click), I get an AV in the client. It might be a bug in the DBX code. I don't know. I can't trace in there. Or perhaps I have initialized the Result from the ServerChannelCallBack.Execute incorrectly. Any assistance is appreciated.
UPDATE
The callback is registered on the client like this:
TFormClient = class(TForm)
CMServerChannel: TDSClientCallbackChannelManager;
...
private
ServerChannelCBID: string;
...
procedure TFormClient.FormCreate(Sender: TObject);
begin
ServerChannelCBID := DateTimeToStr(now);
CMServerChannel.RegisterCallback(
ServerChannelCBID,
ServerChannelCallback.Create
);
...
I'm basing this answer on the DataSnap Server + Client projects which can be downloaded from inside Delphi Seattle using `File | Open from version control'
https://radstudiodemos.svn.sourceforge.net/svnroot/radstudiodemos/branches/RadStudio_XE/Delphi/DataSnap/CallbackChannels
that's mentioned here: http://edn.embarcadero.com/article/41374.
The forms in both the server and client require a slight correction to get them to compile, name to add JSon to their Uses list.
On the server form, I've added the following:
procedure TForm3.Button1Click(Sender: TObject);
var
sr: TStringList;
begin
Inc(CallbackCount); // A form variable
sr := TStringList.Create;
try
sr.Add('Callback: ' + IntToStr(CallbackCount));
sr.Add('two');
ServerContainer1.DSServer1.BroadcastObject('ChannelOne', sr);
finally
// No need for sr.free
end;
end;
(I'm using ChannelOne for consistency with the client)
and on the client I have:
function TCallbackClient.Execute(Arg: TObject): TObject;
var
i: Integer;
begin
// Result := TObject.Create; // is this correct?
Result := TJSONTrue.Create;
try
if Arg is TStringList then
begin
QueueLogValue('Server: Got TStringList');
for i := 0 to TStrings(Arg).Count - 1 do
QueueLogValue('Server:' + TStringList(Arg)[i]);
end;
finally
end;
end;
With those variations from the code you've shown in your q, the server and client run fine, and I can click the server button as many times as I like and neither the server nor any of the clients get "stuck". So I think your problem must be specific to something in the code you are using, but at least the linked project gives you something to work from and compare with.
Btw, I changed the TCallbackClient.Execute return type to TJSONTrue.Create (same as the other override) because that's what it says in Marco Cantu's Delphi 2010 Handbook says it should return, admittedly in the context of a "lightweight" callback while a ServerMethod is executing: returning TJSONFalse tells the server to cancel the executing ServerMethod. However, the callbacks from the server work equally well with the TObject.Create you used.
I'm trying to get a client's IP address and other client information using DSServer's onconnect event with the following code.
My problem is that DSConnectEventObject.ChannelInfo is nil every time. Additionally, I can't resolve the IP addresses.
Please help me. Thank you.
procedure TWebModule1.DSServer1Connect(DSConnectEventObject: TDSConnectEventObject);
var
ci: TDBXClientInfo;
begin
ci := DSConnectEventObject.ChannelInfo.ClientInfo;
AddLog(Format('Client %s Connected IP: %s, Port: %s',
[ci.Protocol, ci.IpAddress, ci.ClientPort])
);
end;
As mentioned previously, this is a bug in DataSnap. It was working fine in XE2 but the error came in somewhere between XE3 and XE5. It has been reported in QC reports #121931 and #126164. Luckily, the client connection properties are available in the Session object - see below :
var
Session: TDSSession;
Protocol, IpAddress, AppName: string;
begin
Session := TDSSessionManager.GetThreadSession;
Protocol := Session.GetData('CommunicationProtocol');
IpAddress := Session.GetData('RemoteIP');
AppName := Session.GetData('RemoteAppName');
end;
how about this?
in WebMoudle unit,
save IP:
implementation
threadvar remoteIP: string;
procedure TWebModule1.WebModuleBeforeDispatch(Sender: TObject;
Request: TWebRequest; Response: TWebResponse; var Handled: Boolean);
begin
remoteIP := Request.RemoteAddr;
end;
procedure TWebModule1.DSServer1Connect(DSConnectEventObject: TDSConnectEventObject);
begin
TDSSessionManager.GetThreadSession.PutData('RemoteAddr', remoteIP);
end;
procedure TWebModule1.DSServer1Disconnect(DSConnectEventObject: TDSConnectEventObject);
begin
remoteIP := '';
end;
DataSnap REST ISAPI dll
in WebMoudle unit,
save IP:
TDSSessionManager.GetThreadSession.PutData('RemoteAddr',Request.RemoteAddr);
in other unit,
get IP:
uIP := TDSSessionManager.GetThreadSession.GetData('RemoteAddr');
This is Bug.
You can do it code, below:
procedure TWebModule.DSServerConnect(
DSConnectEventObject: TDSConnectEventObject);
var _Session: TDSSession;
begin
try
if Assigned(DSConnectEventObject.ChannelInfo) then
begin
_Session := TDSSessionManager.GetThreadSession;
if Assigned(_Session) then
begin
if _Session.GetData('RemoteAddr') = '' then
_Session.PutData('RemoteAddr', DSConnectEventObject.ChannelInfo.Info);
end;
end;
except
end;
end;
I'm having problems trying to use OnUDPRead Event of TIdUDPServer to read broadcast Data sent from a IdUDPClient Client I created. I've tried using the examples shown in the following questions but to no avail.
How can I send a broadcast message in Delphi
Reading data with TIdUDPServer
I'm able to bind TIdUDPServer to the port I specify:
procedure TForm1.Button1Click(Sender: TObject);
begin
IdUDPServer1.BroadcastEnabled := True;
IdUDPServer1.DefaultPort := StrToInt(edit2.Text);
IdUDPServer1.Bindings.Add.IP := '0.0.0.0';
//IdUDPServer1.ThreadedEvent:=True;
IdUDPServer1.Active := True;
end;
IdUDPServer1UDPRead is triggered successfully showing that the UDP Server is working, but I get an exception at this line -> DataStringStream.CopyFrom(AData, AData.Size);
Exception:Access violation at address 004BA415 in module
'IndyUDPReceiver.exe'. Read of address 74736574
procedure TForm1.IdUDPServer1UDPRead(Sender: TObject;
AData: TStream; ABinding: TIdSocketHandle);
var
DataStringStream: TStringStream;
msg: string;
begin
try
DataStringStream := TStringStream.Create('');
try
DataStringStream.CopyFrom(AData, AData.Size);
msg := DataStringStream.DataString;
Memo1.Lines.Add(msg);
finally
DataStringStream.Free;
end;
except
on E: Exception do
begin
Memo1.Lines.Add('Exception:' + E.Message);
DataStringStream.Free;
end;
end;
end;
I've uploaded the full Client and Server to: http://www.2shared.com/file/5SRweGIa/Indy_UDP.html
Grateful for any pointers. :)
Did you, by chance, upgrade your project from an older version of Delphi and/or Indy, and forget to check your event handlers for signature changes? The TIdUDPServer.OnUDPRead event stopped using TStream for its AData parameter a long time ago. It was switched to using TIdBytes instead:
procedure TForm1.IdUDPServer1UDPRead(AThread: TIdUDPListenerThread; const AData: TIdBytes; ABinding: TIdSocketHandle);
var
msg: string;
begin
msg := BytesToString(AData, Indy8BitEncoding);
Memo1.Lines.Add(msg);
end;
A few weeks ago, we had to change the AData parameter for XE3 to finally address an RTTI incompatibility between Delphi and C++ in all 2009+ versions:
procedure TForm1.IdUDPServer1UDPRead(AThread: TIdUDPListenerThread; const AData: array of Byte; ABinding: TIdSocketHandle);
var
msg: string;
begin
msg := BytesToString(AData, Indy8BitEncoding);
Memo1.Lines.Add(msg);
end;
When i send a message from TCPClient to a TCPServer it will be handled using OnExecute event in the server . Now i want to handle the received messages in the Client but TCPClient doesn't have any event for this. So i have to make a thread to handle them manually. how can i do it ?
As others said in response to your question, TCP is not a message oriented protocol, but a stream one. I'll show you how to write and read to a very simple echo server (this is a slightly modified version of a server I did this week to answer other question):
The server OnExecute method looks like this:
procedure TForm2.IdTCPServer1Execute(AContext: TIdContext);
var
aByte: Byte;
begin
AContext.Connection.IOHandler.Writeln('Write anything, but A to exit');
repeat
aByte := AContext.Connection.IOHandler.ReadByte;
AContext.Connection.IOHandler.Write(aByte);
until aByte = 65;
AContext.Connection.IOHandler.Writeln('Good Bye');
AContext.Connection.Disconnect;
end;
This server starts with a welcome message, then just reads the connection byte per byte. The server replies the same byte, until the received byte is 65 (the disconnect command) 65 = 0x41 or $41. The server then end with a good bye message.
You can do this in a client:
procedure TForm3.Button1Click(Sender: TObject);
var
AByte: Byte;
begin
IdTCPClient1.Connect;
Memo1.Lines.Add(IdTCPClient1.IOHandler.ReadLn); //we know there must be a welcome message!
Memo1.Lines.Add('');// a new line to write in!
AByte := 0;
while (IdTCPClient1.Connected) and (AByte <> 65) do
begin
AByte := NextByte;
IdTCPClient1.IOHandler.Write(AByte);
AByte := IdTCPClient1.IOHandler.ReadByte;
Memo1.Lines[Memo1.Lines.Count - 1] := Memo1.Lines[Memo1.Lines.Count - 1] + Chr(AByte);
end;
Memo1.Lines.Add(IdTCPClient1.IOHandler.ReadLn); //we know there must be a goodbye message!
IdTCPClient1.Disconnect;
end;
The next byte procedure can be anything you want to provide a byte. For example, to get input from the user, you can turn the KeyPreview of your form to true and write a OnKeyPress event handler and the NextByte function like this:
procedure TForm3.FormKeyPress(Sender: TObject; var Key: Char);
begin
FCharBuffer := FCharBuffer + Key;
end;
function TForm3.NextByte: Byte;
begin
Application.ProcessMessages;
while FCharBuffer = '' do //if there is no input pending, just waint until the user adds input
begin
Sleep(10);
//this will allow the user to write the next char and the application to notice that
Application.ProcessMessages;
end;
Result := Byte(AnsiString(FCharBuffer[1])[1]); //just a byte, no UnicodeChars support
Delete(FCharBuffer, 1, 1);
end;
Anything the user writes in the form will be sent to the server and then read from there and added to memo1. If the input focus is already in Memo1 you'll see each character twice, one from the keyboard and the other form the server.
So, in order to write a simple client that gets info from a server, you have to know what to expect from the server. Is it a string? multiple strings? Integer? array? a binary file? encoded file? Is there a mark for the end of the connection? This things are usually defined at the protocol or by you, if you're creating a custom server/client pair.
To write a generic TCP without prior known of what to get from the server is possible, but complex due to the fact that there's no generic message abstraction at this level in the protocol.
Don't get confused by the fact there's transport messages, but a single server response can be split into several transport messages, and then re-assembled client side, your application don't control this. From an application point of view, the socket is a flow (stream) of incoming bytes. The way you interpret this as a message, a command or any kind of response from the server is up to you. The same is applicable server side... for example the onExecute event is a white sheet where you don't have a message abstraction too.
Maybe you're mixing the messages abstraction with the command abstraction... on a command based protocol the client sends strings containing commands and the server replies with strings containing responses (then probably more data). Take a look at the TIdCmdTCPServer/Client components.
EDIT
In comments OP states s/he wants to make this work on a thread, I'm not sure about what's the problem s/he is having with this, but I'm adding a thread example. The server is the same as shown before, just the client part for this simple server:
First, the thread class I'm using:
type
TCommThread = class(TThread)
private
FText: string;
protected
procedure Execute; override;
//this will hold the result of the communication
property Text: string read FText;
end;
procedure TCommThread.Execute;
const
//this is the message to be sent. I removed the A because the server will close
//the connection on the first A sent. I'm adding a final A to close the channel.
Str: AnsiString = 'HELLO, THIS IS _ THRE_DED CLIENT!A';
var
AByte: Byte;
I: Integer;
Client: TIdTCPClient;
Txt: TStringList;
begin
try
Client := TIdTCPClient.Create(nil);
try
Client.Host := 'localhost';
Client.Port := 1025;
Client.Connect;
Txt := TStringList.Create;
try
Txt.Add(Client.IOHandler.ReadLn); //we know there must be a welcome message!
Txt.Add('');// a new line to write in!
AByte := 0;
I := 0;
while (Client.Connected) and (AByte <> 65) do
begin
Inc(I);
AByte := Ord(Str[I]);
Client.IOHandler.Write(AByte);
AByte := Client.IOHandler.ReadByte;
Txt[Txt.Count - 1] := Txt[Txt.Count - 1] + Chr(AByte);
end;
Txt.Add(Client.IOHandler.ReadLn); //we know there must be a goodbye message!
FText := Txt.Text;
finally
Txt.Free;
end;
Client.Disconnect;
finally
Client.Free;
end;
except
on E:Exception do
FText := 'Error! ' + E.ClassName + '||' + E.Message;
end;
end;
Then, I'm adding this two methods to the form:
//this will collect the result of the thread execution on the Memo1 component.
procedure TForm3.AThreadTerminate(Sender: TObject);
begin
Memo1.Lines.Text := (Sender as TCommThread).Text;
end;
//this will spawn a new thread on a Create and forget basis.
//The OnTerminate event will fire the result collect.
procedure TForm3.Button2Click(Sender: TObject);
var
AThread: TCommThread;
begin
AThread := TCommThread.Create(True);
AThread.FreeOnTerminate := True;
AThread.OnTerminate := AThreadTerminate;
AThread.Start;
end;
TCP doesn't operate with messages. That is stream-based interface. Consequently don't expect that you will get a "message" on the receiver. Instead you read incoming data stream from the socket and parse it according to your high-level protocol.
Here is my code to Read / Write with Delphi 7. Using the Tcp Event Read.
unit Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls, ScktComp;
type
TForm1 = class(TForm)
ClientSocket1: TClientSocket;
Button1: TButton;
ListBox1: TListBox;
Edit1: TEdit;
Edit2: TEdit;
procedure Button1Click(Sender: TObject);
procedure ClientSocket1Read(Sender: TObject; Socket: TCustomWinSocket);
procedure ClientSocket1Error(Sender: TObject; Socket: TCustomWinSocket;
ErrorEvent: TErrorEvent; var ErrorCode: Integer);
private
{ Private declarations }
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
procedure TForm1.Button1Click(Sender: TObject);
var
UsePort: Integer;
UseHost: String;
begin
UseHost := Edit1.Text;
UsePort := STRTOINT(Edit2.Text);
ClientSocket1.Port := UsePort;
ClientSocket1.Host := UseHost;
ClientSocket1.Active := true;
end;
procedure TForm1.ClientSocket1Read(Sender: TObject;
Socket: TCustomWinSocket);
begin
ListBox1.Items.Add(ClientSocket1.Socket.ReceiveText);
end;
procedure TForm1.ClientSocket1Error(Sender: TObject;
Socket: TCustomWinSocket; ErrorEvent: TErrorEvent;
var ErrorCode: Integer);
begin
ErrorCode:=0;
ClientSocket1.Active := False;
end;
procedure TForm1.BitBtn1Click(Sender: TObject);
begin
ClientSocket1.Socket.SendText(Edit1.Text);
end;
end.
If you need the Indy client to handle incoming "messages" (definition of "message" depends on the protocol used), I recommend to take a look at the implementation of TIdTelnet in the protocols\IdTelnet unit.
This component uses a receiving thread, based on a TIdThread, which asynchronously receives messages from the Telnet server, and passes them to a message handler routine. If you have a similar protocol, this could be a good starting point.
Update: to be more specific, the procedure TIdTelnetReadThread.Run; in IdTelnet.pas is where the asynchronous client 'magic' happens, as you can see it uses Synchronize to run the data processing in the main thread - but of course your app could also do the data handling in the receiving thread, or pass it to a worker thread to keep the main thread untouched. The procedure does not use a loop, because looping / pausing / restarting is implemented in IdThread.
Add a TTimer.
Set its Interval to 1.
Write in OnTimer Event:
procedure TForm1.Timer1Timer(Sender: TObject);
var
s: string;
begin
if not IdTCPClient1.Connected then Exit;
if IdTCPClient1.IOHandler.InputBufferIsEmpty then Exit;
s := IdTCPClient1.IOHandler.InputBufferAsString;
Memo1.Lines.Add('Received: ' + s);
end;
Don't set Timer.Interval something else 1.
Because, the received data deletes after some milliseconds.
I have a Delphi application with a Indy TCPServer and TCPClient. I use the AContext.Bindind.Handle for the identification of each connection (wrong?).
So I have a grid which displayed the connections and I will remove the entry after disconnection:
procedure TfrmMain.serverIndyDisconnect(AContext: TIdContext);
var I:Integer;
begin
for I := 0 to gridClients.RowCount - 1 do
begin
if gridClients.Cells[0, I] = IntToStr(AContext.Binding.Handle) then
begin
gridClients.Rows[I].Delete(I);
end;
end;
WriteLogEntry('Connection closed... (' + AContext.Binding.PeerIP+')');
end;
But in the Disconnect Event, the Handle is already empty (it's ever 401xxxxx, so the last Integer number).
Ideas?
You do not mention which version of Delphi or Indy you are using, but the following holds for D2010 and Indy 10.x.
I've used the "AContext.Data" property for identification of the client. I usually Create an object there and release it when the disconnect event happens.
New OnConnect() code:
procedure TfrmMain.serverIndyConnect(AContext: TIdContext);
begin
AContext.Data := TMyObject.Create(NIL);
// Other Init code goes here, including adding the connection to the grid
end;
Modified OnDisconnect() code below:
procedure TfrmMain.serverIndyDisconnect(AContext: TIdContext);
var I:Integer;
begin
for I := 0 to gridClients.RowCount - 1 do
begin
if gridClients.Cells[0, I] = IntToStr(AContext.Data) then
begin
gridClients.Rows[I].Delete(I);
end;
end;
WriteLogEntry('Connection closed... (' + AContext.Binding.PeerIP+')');
end;