Delphi Charon 1 Communication Example

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An example of simple communication with common TCP/IP device written in Borland Delphi 5 demonstrates simple terminal equipped with NVT (Network Virtual Terminal) support with I/O extensions.

The application is very simple, that is for demonstrative purpose only and you can use it for own applications. Primary focus is on proper solution of TCP/IP parts, including detection of disconnection from server side.

You can control I/O pins by NVT commands in your application (in this example they were used for control of LEDs and for reading of input pins - it covers ON/OFF state of LEDs, too). It's useful, because you don't need to study documentation of NVT commands.

Main form source method description

• procedure ConnectBtnClick(Sender: TObject);
  (* this routine handles press of button Connect/Disconnect, opens socket to the target etc. *)
• procedure ClientSocketConnect(Sender: TObject; Socket: TCustomWinSocket);
  (* this is a callback method to inform the program that connection was succesful. it enables some buttons, like Send text etc. and makes Charon to send <AYT> response *)
• procedure ClientSocketError(Sender: TObject; Socket: TCustomWinSocket; ErrorEvent: TErrorEvent; var ErrorCode: Integer);
  (* callback method, that logs TCP/IP errors on the screen *)
• procedure AYTBtnClick(Sender: TObject);
  (* method, that sends the request to the Charon *)
• procedure ClientSocketRead(Sender: TObject; Socket: TCustomWinSocket);
  (* callback method that parses received data from TCP/IP connection *)
• procedure WriteLEDBtnClick(Sender: TObject);
  (* method providing set of outputs at Charon according to state of the checkboxes *)
• procedure FormClose(Sender: TObject; var Action: TCloseAction);
  (* callback method, that is called while program is terminating. it cleans up the environment, closes socket etc. *)
• procedure ClearBtnClick(Sender: TObject);
  (* this method clears the log window *)
• procedure ReadLEDBtnClick(Sender: TObject);
  (* method that sends a request for Charon to return state of the input lines *)
• procedure SendBtnClick(Sender: TObject);
  (* method that sends the string from input line to the Charon's serial output *)
• procedure FormCreate(Sender: TObject);
  (* callback method that initializes form's data *)
• procedure FormDestroy(Sender: TObject);
  (* callback method that destroys form's data *)
• procedure CloseBtnClick(Sender: TObject);
  (* method that provides terminating of the program *)
• procedure Label4Click(Sender: TObject);
  procedure Label6Click(Sender: TObject);
  procedure Label7Click(Sender: TObject);
  (* these three methods invoke WWW browser or e-mail client to respond to the advertisement user clicks *)
• procedure ClientSocketDisconnect(Sender: TObject; Socket: TCustomWinSocket);
  (* callback method that provides disconnect handling, like setting buttons disabled etc. *)
• procedure HandleButtons( Active : boolean );
  (* method that sets enabled/disabled state of many buttons - it simplifies the code by collecting standard responses to one spot *)

Download of source and binary codes

• dphi_ch1com_example.zip
     \MainForm.pas, MainForm.dfm, Charon.dpr and other resources
     \Program\Charon.exe, Charon.ini