Can't send text(string) from ttcpserver to ttcpclientserver

Question

I have 2 forms, 1 for server another for client. After dropping ttcpserver on server form and setting its localhost property to 127.0.0.1 and localport property to 55555 and Active property to true I wrote a button1(sendtextbutton) onclick event handler:

procedure TForm2.Button1Click(Sender: TObject);
begin
      TcpServer1.Sendln('message');
end;

Then on client form I dropped 1 ttcpclient 1 label 2 buttons, set clients remote host property to 127.0.0.1 and remote port to 55555, wrote an event handler for connectbutton(button1):

procedure TForm2.Button1Click(Sender: TObject);
begin
try
TcpClient1.Active := true;
except
showmessage('error');

end;
end;

Wrote an onconnect event for ttcpclient:

procedure TForm2.TcpClient1Connect(Sender: TObject);
begin
    Label1.Caption := 'connected!';
end;

and then finally an onrecieve event hadler for ttcpclient:

procedure TForm2.TcpClient1Receive(Sender: TObject; Buf: PAnsiChar;
  var DataLen: Integer);
begin
    Label1.caption := TcpClient1.Receiveln();
end;

My client programs caption was supposed to change to 'message'(after I connect and click button on my server form), but it doest. Am I doing it the wrong way? If yes, then how to do it? I am trying to send a text message from server to client(Yes a reverse connection!)

Answer 1

TTcpServer does not store a list of connected connection which make broadcast style messages difficult.

I would recommend switching to TidTcpServer and TidTcpClient. The TidTcpServer component has a Context Property that you can loop through to broadcast messages to the clients similar to what you seem to want to do.

Here some links to examples of using TidTcpServer and TIdTcpClient:

• Exchanging Data over the Network using Delphi
• Get Image from Client with Indy Socket
• New and Improved Screen Thief 2
• Indy Demo's Downloads'

Answer 2

Your server code does not work because TTcpServer.SendLn() does not send the data to the client's endpoint of the connected socket. That is why the client never sees the data - it is being sent into limbo.

If the TTcpServer.BlockMode property is set to bmThreadBlocking (which it is by default), or if the TTcpServer.BlockMode is set to anything else and you are manually calliing the parameterless overloaded TTcpServer.Accept() method, then the only place you have access to the client's endpoint is from inside the TTcpServer.OnAccept event. Under these conditions, when that event handler exits, the server will disconnect the client, so any work the server wants to do with the client must be done from inside that event.

If that does not suit your needs, then you will have to set the TTcpServer.BlockMode property to either bmBlocking or bmNonBlocking and then manually call the overloaded TTcpServer.Accept() method that returns a TCustomIpClient object. After the TTcpServer.OnAccept event has been triggered and exited, you will gain ownership of that object and have full control over its lifetime and can then access it whenever and however you want.