Command Event

Description

When the AutoOption property is set to False, the Telnet Control does not respond to Telnet commands, but instead fires the Command event. The application must have the appropriate code within this event to handle all option negotiation. The presence of this event allows the user to write sophisticated Telnet clients that can support any desired option, as well as Telnet server applications. The SendCommand method is used to send Telnet option negotiation sequences and commands.

Syntax

Visual Basic
Public Event Command( _ ByVal Command As CommandConstants, _ ByVal Opt As OptionConstants, _ ByRef SubOption As Variant _ )

Visual Basic

Public Event Command( _
   ByVal Command As CommandConstants, _
   ByVal Opt As OptionConstants, _
   ByRef SubOption As Variant _
)

Parameters

Command

Value	Description
telnetAbortOutput	The function AO.
telnetAreYouThere	The function AYT.
telnetBreak	Network Virtual Terminal (NVT) BRK.
telnetDataMark	The data stream portion of a Synch.
telnetDo	Ask the Telnet host to DO the specified option.
telnetDont	Ask the Telnet host to NOT DO the specified option.
telnetEraseCharacter	The function EC.
telnetEraseLine	The function EL.
telnetGoAhead	The GA Signal.
telnetIac	The Interpret as Command signal.
telnetInterruptProcess	The function IP.
telnetNoOperation	The Telnet client WILL agree to the specified option.
telnetSubOption	Indicates that what follows is sub-negotiation of the indicated option.
telnetSubOptionEnd	End of sub-negotiation parameters (not used by application)
telnetWill	The Telnet client WILL agree to the specified option.
telnetWont	The Telnet client WONT agree to the specified option.

The command value received.

Opt

Value	Description
telnet3270Regime	Controls the 3270 Regime option.
telnetAuthentication	Controls the Authentication option.
telnetByteMacro	Controls the Byte Macro option.
telnetCharacterSet	Controls the Character Set option.
telnetComPort	Controls the COM Port option.
telnetDataEntryTerminal	Controls the Data Entry Terminal option.
telnetEcho	Controls echoing
telnetEndOfRecord	Controls the end of record option.
telnetEnvironment	Controls the Enviroment option.
telnetExtendedASCII	Controls the Extended ASCII option.
telnetExtendedOptionsList	Controls the Extended Options List option.
telnetLineMode	Controls the Line Mode option.
telnetLogout	Controls the Logout option.
telnetNewEnvironment	Controls the New Environment option.
telnetOutputMarking	Controls the Output Marking option.
telnetSendLocation	Controls the Send Location option.
telnetStatus	Controls the Status option.
telnetSUPDUPOutput	Controls the SUPDUP Output option.
telnetSupressGoAheads	Suppresses GoAhead signalling
telnetTACACSUserIdentification	Controls the TACACS User Identification option.
telnetTerminalLocation	Controls the Terminal Location option.
telnetTerminalType	Controls terminal type
telnetTimingMark	Controls the Timing Mark option.
telnetToggleFlowControl	Controls the Flow Control option.
telnetTransmitBinary	Controls the Transmit Binary option
telnetWindowSize	Controls terminal window size
telnetX3Pad	Controls the X.3 Pad option.
telnetXDisplayLocation	Controls the X Display Location.

If Command is telnetDo, telnetDont, telnetWill or telnetWont, then this is the specified option.

SubOption

Variant. If Command is telnetSubOption, then this is the suboption sequence in a Byte array.

Example

Example (Visual Basic)

Private Sub Telnet1_Command(ByVal Command As DartTelnetCtl.CommandConstants, ByVal Opt As DartTelnetCtl.OptionConstants, SubOption As Variant)
On Error GoTo OnError ' use intrinsic error handling
	Select Case Command
	Case telnetSubOptionEnd
		' server wants to negotiate a sub-option
		If Opt = telnetTerminalType Then
			' negotiate TermType suboption for VT320
			Telnet1.SendCommand telnetSubOption, Opt, Chr$(0) & "vt320"
		ElseIf Opt = telnetWindowSize Then
			' want the server to set a window size of 80x32
			Telnet1.SendCommand telnetSubOption, Opt, Chr$(0) & Chr$(80) & Chr$(0) & Chr$(32)
		End If
	Case telnetDo
		' server wants us to enable an option
		If Opt = telnetTerminalType Then
			' want to subnegotiate TermType
			Telnet1.SendCommand telnetWill, Opt
		ElseIf Opt = telnetWindowSize Then
			' want to subnegotiate Window Size
			Telnet1.SendCommand telnetWill, Opt
		Else
			' refuse any other option being requested
			Telnet1.SendCommand telnetWont, Opt
		End If
	Case telnetDont
		' server wants to disable option&ldots;agree to it
		Telnet1.SendCommand telnetWont, Opt
	Case telnetWill
		' server wants to enable an option
		If Opt = telnetSupressGoAheads Then
			' do suppress go-aheads
			Telnet1.SendCommand telnetDo, Opt
		ElseIf Opt = telnetEcho Then
			' do echo characters sent
			Telnet1.SendCommand telnetDo, Opt
		Else
			' we don't agree to anything else
			Telnet1.SendCommand telnetDont, Opt
		End If
	Case telnetWont
		' fine with us
		Telnet1.SendCommand telnetDont, Opt
	End Select
	Exit Sub
OnError: ' Any error jumps here
	Debug.Print "Error #" + CStr(Err.Number) + ": " + Err.Description
End Sub