else
        Result := wsInvalidState;
end;


{* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *}
procedure TTnCnx.SocketSessionConnected(Sender: TObject; Error : word);
begin
    if Assigned(FOnSessionConnected) then
        FOnSessionConnected(Self, Error);
end;


{* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *}
procedure TTnCnx.SocketSessionClosed(Sender: TObject; Error : word);
begin
    if Socket.State <> wsClosed then
        Socket.Close;
    if Assigned(FOnSessionClosed) then
        FOnSessionClosed(Self, Error);
end;


{* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *}
procedure TTnCnx.SocketDataAvailable(Sender: TObject; Error : word);
var
    Len, I : Integer;
    Buffer : array [1..2048] of char;
    Socket : TWSocket;
begin
    Socket := Sender as TWSocket;
    Len := Socket.Receive(@Buffer[1], High(Buffer));
    if Len = 0 then begin
        { Remote has closed }
        Display(#13 + #10 + '**** Remote has closed ****' + #13 + #10);
    end
    else if Len < 0 then begin
        { An error has occured }
        if Socket.LastError <> WSAEWOULDBLOCK then
            Display(#13 + #10 + '**** ERROR: ' + IntToStr(Socket.LastError) +
                    ' ****' + #13 + #10);
    end
    else begin
        for I := 1 to Len do
            ReceiveChar(Buffer[I]);
        FlushBuffer;
    end;
end;


{* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *}
function  TTnCnx.Send(Data : Pointer; Len : Integer) : integer;
begin
    if Assigned(Socket) then
        Result := Socket.Send(Data, Len)
    else
        Result := -1;
end;


{* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *}
function TTnCnx.SendStr(Data : String) : integer;
begin
    Result := Send(@Data[1], Length(Data));
end;


{* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *}
procedure TTnCnx.Answer(chAns : Char; chOption : Char);
var
    Buf   : String[3];
begin
{    DebugString('Answer ' + IntToHex(ord(chAns), 2) + ' ' + IntToHex(ord(ChOption), 2) + #13 + #10); }
    Buf := TNCH_IAC + chAns + chOption;
    Socket.Send(@Buf[1], Length(Buf));
end;


{* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *}
procedure TTnCnx.WillOption(chOption : Char);
begin
    Answer(TNCH_WILL, chOption);
end;


{* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *}
procedure TTnCnx.WontOption(chOption : Char);
begin
    Answer(TNCH_WONT, chOption);
end;


{* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *}
procedure TTnCnx.DontOption(chOption : Char);
begin
    Answer(TNCH_DONT, chOption);
end;


{* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *}
procedure TTnCnx.DoOption(chOption : Char);
begin
    Answer(TNCH_DO, chOption);
end;


{* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *}
procedure TTnCnx.NegociateSubOption(strSubOption : String);
var
    Buf   : String;
begin
{    DebugString('SubNegociation ' +
                IntToHex(ord(strSubOption[1]), 2) + ' ' +
                IntToHex(ord(strSubOption[2]), 2) + #13 + #10); }

    case strSubOption[1] of
    TN_TERMTYPE:
        begin
            if strSubOption[2] = TN_TTYPE_SEND then begin
{                DebugString('Send TermType' + #13 + #10); }
                if Assigned(FOnTermType) then
                    FOnTermType(Self);
                Buf := TNCH_IAC + TNCH_SB + TN_TERMTYPE + TN_TTYPE_IS + FTermType + TNCH_IAC + TNCH_SE;
                Socket.Send(@Buf[1], Length(Buf));
            end;
        end;
    else
{        DebugString('Unknown suboption' + #13 + #10); }
    end;
end;


{* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *}
procedure TTnCnx.NegociateOption(chAction : Char; chOption : Char);
var
    Buf : String;
begin
{    DebugString('Negociation ' + IntToHex(ord(chAction), 2) + ' ' +
                                 IntToHex(ord(ChOption), 2) + #13 + #10); }

    case chOption of
    TN_TRANSMIT_BINARY:
        begin
            if chAction = TNCH_WILL then begin
                Answer(TNCH_DO, chOption);
                RemoteBinMode := TRUE;
                LocalBinMode  := TRUE;
            end
            else if chAction = TNCH_WONT then begin
                if RemoteBinMode then begin
                    RemoteBinMode := FALSE;
                    LocalBinMode  := FALSE;
                end;
            end;
        end;
    TN_ECHO:
        begin
            if chAction = TNCH_WILL then begin
                Answer(TNCH_DO, chOption);
                FLocalEcho := FALSE;
            end
            else if chAction = TNCH_WONT then begin
                FLocalEcho := TRUE;
            end;
            if Assigned(FOnLocalEcho) then
                FOnLocalEcho(self);
        end;
    TN_SUPPRESS_GA:
        begin
            if chAction = TNCH_WILL then begin
                Answer(TNCH_DO, chOption);
                spga := TRUE;
            end;
        end;
    TN_TERMTYPE:
        begin
            if chAction = TNCH_DO then begin
                Answer(TNCH_WILL, chOption);
                FTType := TRUE;
            end;
        end;
    TN_SEND_LOC:
        begin
            if chAction = TNCH_DO then begin
                Answer(TNCH_WILL, chOption);
                if Assigned(FOnSendLoc) then
                    FOnSendLoc(Self);
                Buf := TNCH_IAC + TNCH_SB + TN_SEND_LOC + FLocation + TNCH_IAC + TNCH_SE;
                Socket.Send(@Buf[1], Length(Buf));
            end;
        end;
    TN_EOR:
        begin
            if chAction = TNCH_DO then begin
                Answer(TNCH_WILL, chOption);
                FTType := TRUE;
            end;
        end;
    else
{        Answer(TNCH_WONT, chOption); }
        { Jan Tomasek <xtomasej@feld.cvut.cz> }
        if chAction = TNCH_WILL then
            Answer(TNCH_DONT, chOption)
        else
            Answer(TNCH_WONT, chOption);
    end;
end;


{* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *}
procedure TTnCnx.FlushBuffer;
var
    Buffer : PChar;
    Count  : Integer;
begin
    try
        if FBufferCnt > 0 then begin
            if Assigned(FOnDataAvailable) then begin
                { We need to make a copy for the data because we can reenter   }
                { during the event processing                                  }
                Count := FBufferCnt;             { How much we received        }
                try
                    GetMem(Buffer, Count + 1);       { Alloc memory for the copy   }
                except
                    Buffer := nil;
                end;
                if Buffer <> nil then begin
                    try
                        Move(FBuffer, Buffer^, Count);   { Actual copy             }
                        Buffer[Count] := #0;             { Add a nul byte          }
                        FBufferCnt := 0;                 { Reset receivecounter    }
                        FOnDataAvailable(Self, Buffer, Count); { Call event handler  }
                    finally
                        FreeMem(Buffer, Count + 1);      { Release the buffer      }
                    end;
                end;
            end
            else begin
                FBufferCnt := 0
            end;
        end;
    except
        raise;
    end;
end;


{* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *}
procedure TTnCnx.AddChar(Ch : Char);
begin
    FBuffer[FBufferCnt] := Ch;
    Inc(FBufferCnt);
    if FBufferCnt >= SizeOf(FBuffer) then
        FlushBuffer;
end;


{* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *}
procedure TTnCnx.ReceiveChar(Ch : Char);
const
    bIAC         : Boolean = FALSE;
    chVerb       : Char    = #0;
    strSubOption : String  = '';
    bSubNegoc    : Boolean = FALSE;
begin
    if chVerb <> #0 then begin
        NegociateOption(chVerb, Ch);
        chVerb       := #0;
        strSubOption := '';
        Exit;
    end;

    if bSubNegoc then begin
        if Ch = TNCH_SE then begin
            bSubNegoc    := FALSE;
            NegociateSubOption(strSubOption);
            strSubOption := '';
        end
        else
            strSubOption := strSubOption + Ch;
        Exit;
    end;

    if bIAC then begin
        case Ch of
        TNCH_IAC: begin
                      AddChar(Ch);
                      bIAC := FALSE;
                  end;
        TNCH_DO, TNCH_WILL, TNCH_DONT, TNCH_WONT:
                  begin
                      bIAC   := FALSE;
                      chVerb := Ch;
                  end;
        TNCH_EOR:
            begin
                DebugString('TNCH_EOR' + #13 + #10);
                bIAC   := FALSE;
                if Assigned(FOnEOR) then
                    FOnEOR(Self);
            end;
        TNCH_SB:
            begin
{                DebugString('Subnegociation' + #13 + #10); }
                bSubNegoc := TRUE;
                bIAC      := FALSE;
            end;
        else
            DebugString('Unknown ' + IntToHex(ord(Ch), 2) + ' ''' + Ch + '''' + #13 + #10);
            bIAC := FALSE;
        end;

        Exit;
    end;

    case Ch of
    TNCH_EL:
        begin
            DebugString('TNCH_EL' + #13 + #10);
            AddChar(Ch);
        end;
    TNCH_EC:
        begin
            DebugString('TNCH_EC' + #13 + #10);
            AddChar(Ch);
        end;
    TNCH_AYT:
        begin
            DebugString('TNCH_AYT' + #13 + #10);
            AddChar(Ch);
        end;
    TNCH_IP:
        begin
            DebugString('TNCH_IP' + #13 + #10);
            AddChar(Ch);
        end;
    TNCH_AO:
        begin
            DebugString('TNCH_AO' + #13 + #10);
            AddChar(Ch);
        end;
    TNCH_IAC:
        begin
            bIAC := TRUE
        end;
    else
        AddChar(Ch);
    end;
end;


{* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *}

end.