2. Starting the program

Setting up the operating elements
At first the group with the operating elements for the Web-IO is blocked from use. The status line indicates that there is not yet a connection.

procedure Twebio_ascii_client.FormCreate(Sender:TObject);
begin
	StatusBar1.SimpleText := 'No Connection';
	bt_disconnect.Enabled := False;
	gb_io.Enabled := False;
end;

3. Connection control

• Establishing the connection

  The connection is opened by entering the IP address of the Web-IO in the text field ed_ip and clicking on the bt_connect button.

  procedure Twebio_ascii_client.bt_connectClick(Sender:TObject);
  begin
  	if ed_ip.Text <> '' then
  		begin
  		ClientSocket1.Host := ed_ip.Text;
  		ClientSocket1.Port := strtoint(ed_port.Text);
  		ClientSocket1.Active := True;
  		end;
  end;

• Connection is made

  As soon as the Web-IO accepts the connection, the ClientSocket control element carries out the corresponding procedure. The status line indicates that the connection has been established, the control elements are enabled for use and the Disconnect button is active again.

  procedure Twebio_ascii_client.ClientSocket1Connect(Sender:TObject;Socket: TCustomWinSocket);
  begin
  	StatusBar1.SimpleText := 'Connected to ' + ed_ip.Text;
  	bt_disconnect.Enabled := True;
  	gb_io.Enabled := True;
  end;

• Opening the connection

  The Delphi ClientSocket control is used for executing TCP/IP handling.
  This control allows procedures to be specified and started when various connection states occur, here for example for attempting to open a connection. The procedure enters a corresponding message in the status line and deactivates the bt_connect button so that the user cannot start another connection attempt while the first one is still running.

  procedure Twebio_ascii_client.ClientSocket1Connecting(Sender:TObject;Socket: TCustomWinSocket);
  begin
  	StatusBar1.SimpleText := 'Try to connect to ' + ed_ip.Text;
  	bt_connect.Enabled := False;
  end;

• Connection is made

  As soon as the Web-IO accepts the connection, the ClientSocket control element carries out the corresponding procedure. The status line indicates that the connection has been established, the control elements are enabled for use and the Disconnect button is active again.

  procedure Twebio_ascii_client.ClientSocket1Connect(Sender:TObject;Socket: TCustomWinSocket);
  begin
  	StatusBar1.SimpleText := 'Connected to ' + ed_ip.Text;
  	bt_disconnect.Enabled := True;
  	gb_io.Enabled := True;
  end;

• Disconnecting

  The connection remains open until it is ended by the user clicking on the Disconnect button, or the Web-IO ends the connection.

  procedure Twebio_ascii_client.bt_disconnectClick(Sender:TObject);
  begin
  	ClientSocket1.Active := False;
  end;

  Here again the ClientSocket control element invokes a corresponding procedure

  procedure Twebio_ascii_client.ClientSocket1Disconnect(Sender:TObject;Socket: TCustomWinSocket);
  begin
  	ClientSocket1.Active := False;
  	StatusBar1.SimpleText := 'No Connection';
  	bt_connect.Enabled := True;
  	bt_disconnect.Enabled := False;
  	gb_io.Enabled := False;
  end;

• Connection error

  Also in case of a connection error the ClientSocket control element carries out a corresponding procedure which is essentially like the Disconnect procedure. The status line also indicates the Winsock error number and the ErrorCode is then set to 0 so that no runtime error occurs.

  procedure Twebio_ascii_client.ClientSocket1Error(Sender:TObject;Socket: TCustomWinSocket; ErrorEvent: TErrorEvent;var ErrorCode: Integer);
  begin
  	ClientSocket1.Active := False;
  	StatusBar1.SimpleText := 'Error ' + inttostr(ErrorCode) + ' - No Connection';
  	ErrorCode := 0;
  	bt_connect.Enabled := True;
  	bt_disconnect.Enabled := False;
  	gb_io.Enabled := False;
  end;

4. Operation and communication from the client side

As soon as a connection is made with the Web-IO, the user can use the corresponding program elements to send commands to the Web-IO

• Setting the outputs

  The user sets the outputs by using the two check boxes cb_outputx. The program uses the MouseUP event of this object. If a Mouse Up, i.e. releasing the output check box, is recorded, the program carries out the corresponding procedure and – depending on whether the check box is set or not – passes the appropriate command to the Web-IO.

  procedure Twebio_ascii_client.cb_outputMouseUp(Sender:TObject;Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
  begin
  	if sender = cb_output0 then
  		if cb_output0.Checked then
  			ClientSocket1.Socket.SendText('GET/outputaccess0?PW=' + ed_password.Text + '&State=ON&')
  		else
  			ClientSocket1.Socket.SendText('GET/outputaccess0?PW=' + ed_password.Text + '&State=OFF&')
  	else
  		if cb_output1.Checked then
  			ClientSocket1.Socket.SendText('GET/outputaccess1?PW=' + ed_password.Text + '&State=ON&')
  		else
  			ClientSocket1.Socket.SendText('GET/outputaccess1?PW=' + ed_password.Text + '&State=OFF&');
  end;

• Query output/input status

  The user can request the status of the outputs and inputs by clicking on the corresponding button.

  procedure Twebio_ascii_client.bt_outputs_readClick(Sender:TObject);
  begin
  	ClientSocket1.Socket.SendText('GET/output?PW=' + ed_password.Text + '&');
  end;

  procedure Twebio_ascii_client.bt_inputs_readClick(Sender:TObject);
  begin
  	ClientSocket1.Socket.SendText('GET/input?PW=' + ed_password.Text + '&');
  end;

• Read clear counters

  Also the counter states of the input counters can be read or cleared.

  procedure Twebio_ascii_client.bt_counter_readClick(Sender:TObject);
  begin
  	if sender = bt_counter_read0 then
  		ClientSocket1.Socket.SendText('GET/counter0?PW=' + ed_password.Text + '&')
  	else
  		ClientSocket1.Socket.SendText('GET/counter1?PW=' + ed_password.Text + '&');
  end;

  procedure Twebio_ascii_client.bt_counter_clearClick(Sender:TObject);
  	begin
  		if sender = bt_counter_clear0 then
  			ClientSocket1.Socket.SendText('GET /counterclear0?PW='+ ed_password.Text + '&')
  		else
  			ClientSocket1.Socket.SendText('GET /counterclear1?PW='+ ed_password.Text + '&');
  	end;

  Of course all the counters can be read or cleared at the same time.

  procedure Twebio_ascii_client.bt_counter_readallClick(Sender:TObject);
  begin
  	ClientSocket1.Socket.SendText('GET/counter?PW=' + ed_password.Text + '&')
  end;

  procedure Twebio_ascii_client.bt_counter_clearallClick(Sender:TObject);
  begin
  	ClientSocket1.Socket.SendText('GET /counterclear?PW=' + ed_password.Text + '&')
  end;

5. Data reception from the Web-IO

Process and display the received data

All commands and requests to the Web-IO are acknowledged with a reply string. The replies have a specific structure depending on the type.

• For the outputs: output;<binary value of the output status in hexadecimal format>
• For the inputs: input;<binary value of the input status in hexadecimal format>
• For the counters: counterx;<decimal counter state>
• or counter;<decimal counter state 0 >; <decimal counter state 0 >;…..if you want to read all counters at the same time.
• All reply strings are finished off with a 0 byte.
• If data are received from the ClientSocket control element, the latter invokes the corresponding procedure

procedure Twebio_ascii_client.ClientSocket1Read(Sender:TObject;Socket: TCustomWinSocket);
var ReceiveString : String;
	OutputValue : word;
	InputValue : word;
begin
	ReceiveString := ClientSocket1.Socket.ReceiveText;
	if Receivestring[1] = 'o' then
		begin
		OutputValue := HextoInt(copy(ReceiveString,pos(';',ReceiveString)+1,length(ReceiveString)-pos(';',ReceiveString)-1));
			if OutputValue and 1 = 1 then
				cb_output0.Checked := True
			else
				cb_output0.Checked := False;
			if OutputValue and 2 = 2 then
				cb_output1.Checked := True
			else
				cb_output1.Checked := False;
		end;
	if Receivestring[1] = 'i' then
		begin
		InputValue := HextoInt(copy(ReceiveString,pos(';',ReceiveString)+1,length(ReceiveString)-pos(';',ReceiveString)-1));
			if InputValue and 1 = 1 then
				cb_input0.Checked := True
			else
				cb_input0.Checked := False;
			if InputValue and 2 = 2 then
				cb_input1.Checked := True
			else
				cb_input1.Checked := False;
		end;
	if Receivestring[1] = 'c' then
		begin
		if copy(ReceiveString, 8, 1) = '0'then
			ed_counter0.Text := copy(ReceiveString,10,length(ReceiveString)-10);
		if copy(ReceiveString, 8, 1) = '1'then
			ed_counter1.Text := copy(ReceiveString,10,length(ReceiveString)-10);
		if copy(ReceiveString, 8, 1) = ';'then
			begin
				ReceiveString[8] := ' ';
				ed_counter0.Text := copy(ReceiveString,9, pos(';',ReceiveString)-9);
				ed_counter1.Text := copy(ReceiveString, pos(';',ReceiveString)+1,length(ReceiveString)-pos(';',ReceiveString)-1);
			end;
		end;
end;

The receiving procedure uses the first character of the receive data to check whether this is an input, output or counter message. Depending on this it is determined for example which output has which status. Since the output status is sent in hexadecimal format, a conversion into an integer value is first required in order to calculate subsequent steps. For the conversion a corresponding function is incorporated in the program. In the case of the counters it is also possible to read individual counter values or to read out all the counters at once. The individual counter states are then output in decimal format in a semicolon delimited string.

function HexToInt(HexString: String) : longWord;
var CharCount : integer;
	HexCharValue : longWord;
	HexValue : longWord;
begin
	HexValue := 0;
	HexString := UpperCase(HexString);
	for CharCount := 1 to length(HexString) do
	begin
		HexCharValue := ord(HexString[CharCount]);
		if HexCharValue > 57 then
			HexCharValue := HexCharValue -55
		else
			HexCharValue := HexCharValue -48;
			HexCharValue := HexCharValue shl ((length(HexString)- CharCount) * 4);
			HexValue := HexValue or HexCharValue;
	end;
	HexToInt := HexValue;
end;

6. Polling

Cyclical polling of particular values

In order to enable automatic refreshing of the display, a timer is used.
Depending on the check boxes for output, input and counter polling, the corresponding information is obtained from the Web-IO at a set interval.

procedure Twebio_ascii_client.timer_pollingTimer(Sender:TObject);
begin
	if	ClientSocket1.Active and cb_output_polling.Checked then
			ClientSocket1.Socket.SendText('GET /output?PW=' + ed_password.Text + '&');
	if	ClientSocket1.Active and cb_input_polling.Checked then
			ClientSocket1.Socket.SendText('GET /input?PW=' + ed_password.Text + '&');
	if	ClientSocket1.Active and cb_counter_polling.Checked then
			ClientSocket1.Socket.SendText('GET /counter?PW=' + ed_password.Text + '&');
end;

The desired interval can be entered in the corresponding text field. When changes are made the timer interval is automatically adjusted.

procedure Twebio_ascii_client.ed_intervalChange(Sender:TObject);
begin
	timer_polling.Interval := strtoint(ed_interval.Text);
end;

The sample program supports all common functions of the Web-IO in command string mode, optimized for the Web-IO 2x Digital Input, 2x Digital Output PoE. For the other Web-IO models you may have to adapt the program. Additional program examples for socket programming can be found on the tool pages for the Web-IO. A detailed description for the socket interface of the Web-IO Digital models can be found in the reference manual.