As the successor to Borland Delphi, Delphi 2005 builds on the Microsoft.net Framework. Delphi 2005 (Delphi.net) offers everything needed to program TCP/IP applications. This makes Delphi 2005 a favorite tool for creating applications that communicate with the Web-IO Digital. Additional drivers or DLLs are not required.
Using the following program example you can represent your Web-IO Digital with its inputs and outputs in a Windows application. You can also switch the Web-IO outputs.
You don’t have a Web-IO yet but would like to try the example out sometime?
No problem: We will be glad to send you the Web-IO Digital 2xInput, 2xOutput at no charge for 30 days. Simply fill out a sample ordering form, and we will ship the Web-IO for testing on an open invoice. If you return the unit within 30 days, we will simply mark the invoice as paid.
assigned it an IP address - which with WuTility is no problem.
1. Combining the various operating elements and display objects in the VB.net form
In addition to the objects shown here, the program also needs a timer for polling (timer_polling).
When naming the individual objects it is helpful to use logical names. In this example the first part of the name describes the type of object and the second part the function.
1. Starting the program
While constructing graphical user interfaces in Delphi 2005 is just as simple to accomplish as with the older Delphi versions, constructing network communication under Delphi.net is somewhat more difficult. This is due primarily to the fact that the ClientSocket control element for framework applications is no longer provided. Instead, you must specify the namespace for the socket classes in the uses area in order to have network access.
Some procedures which are not created by Delphi itself must be declared in the header of the source text. (More on the content of these procedures later)
Furthermore, the socket on which communication is supposed to take place needs to be created and a buffer for the input data and AsyncResult variable must be defined.
var
TCP_Client : Socket;
ReceiveBuffer : array
[0..512] of byte;
ar : IAsyncResult;
2. Connection control
Establishing the connection The connection is opened by entering the IP address of the Web-IO in the text field tb_ip and clicking on the bt_connect button.
procedure TWinForm.bt_connect_Click(sender:
System.Object; e: System.EventArgs); var WebioEP : IPEndPoint; begin if (tb_ip.Text <>
'') and (tb_port.Text <>
'') then begin
bt_connect.Enabled := false;
WebioEP := IPEndPoint.Create(IPaddress.Parse(tb_ip.Text),
convert.ToInt16(tb_port.Text ));
TCP_Client := Socket.Create (AddressFamily.InterNetwork,
SocketType.Stream,
ProtocolType.TCP);
StatusBar1.Text := 'Try
to connect to ' + tb_ip.Text;
timer_polling.Enabled := true; try
TCP_Client.BeginConnect(WebioEP,
callback_connect, TCP_Client); excepton ex : Exception do begin
StatusBar1.Text
:= 'ERROR on connecting';
close(); end; end; end; end;
Opening the connection For TCP/IP handling first an IPEndPoint is defined from IP address and TCP port and used to initialize the TCP_client socket. As part of the connection request a reference to a callback procedure is created.
Connection is made As soon as a connection is made with the Web-IO, the callback procedure is run. The status line shows that the connection has been opened, the operating elements are enabled for use and the Disconnect button becomes operable. The Connect button is blocked for operation. In addition a reference to a callback routine for data reception is created.
procedure
TWinForm.callback_connect(ari : IAsyncResult); begin
gb_io.enabled := true;
bt_disconnect.Enabled := True;
statusbar1.Text := 'Connected to
' + tb_ip.Text; try
TCP_Client.EndConnect(ari);
TCP_Client.BeginReceive(ReceiveBuffer, 0,
512,
SocketFlags.None, callback_readdata, ari.AsyncState); excepton
ex : Exception do begin
StatusBar1.Text := 'ERROR
on connect: ' + ex.ToString;
close(); end; end; 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
TWinForm.bt_disconnect_Click(sender: System.Object; e: System.EventArgs); begin
close(); end;
In this case a corresponding procedure is invoked.
Connection error All actions pertaining to TCP/IP communication are executed within the Try instruction. If errors occur, the CloseConnection procedure is likewise invoked.
3. 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.
procedure TWinForm.sendcommand(sendstring
: String); var
SendBuffer : array
[0..512] of byte; begin
SendBuffer := System.Text.Encoding.ASCII.GetBytes(sendstring); try
TCP_Client.Send(SendBuffer, 0, sendstring.Length,
SocketFlags.None ); except on ex : Exception do begin
StatusBar1.Text := 'ERROR
on send: ' + ex.ToString;
close(); end; end; end;
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 MouseUp, i.e. releasing the output check box, is used, 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 TWinForm.cb_output0_MouseUp(sender:
System.Object; e: System.Windows.Forms.MouseEventArgs); begin if cb_output0.Checked
Then
sendcommand('GET /outputaccess0?PW='
+ tb_password.Text + '&State=ON&') else
sendcommand('GET /outputaccess0?PW='
+ tb_password.Text + '&State=OFF&'); end;
procedure TWinForm.cb_output1_MouseUp(sender:
System.Object; e: System.Windows.Forms.MouseEventArgs); begin if cb_output1.Checked
Then
sendcommand('GET /outputaccess1?PW='
+ tb_password.Text + '&State=ON&') else
sendcommand('GET /outputaccess1?PW='
+ tb_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.
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.
When data are received the corresponding Callback procedure is invoked
procedure
TWinForm.callback_readdata(ari : IAsyncResult); var
bytesread : Integer;
receivestring : string; begin try
bytesread := TCP_Client.EndReceive(ari) except end; if Bytesread = 0 then
close() else begin
receivestring :=
System.Text.Encoding.ASCII.GetString(ReceiveBuffer,0,
bytesread); try
TCP_Client.BeginReceive(ReceiveBuffer,
0, 512,
SocketFlags.None, callback_readdata,
ari.AsyncState); excepton ex : Exception do begin
statusbar1.Text :=
'ERROR on read: ' + ex.ToString;
close(); end;
end; if receivestring[1]
= 'o' then begin if
(convert.ToInt16(receivestring[8]) and
1) = 1 then
cb_output0.Checked
:= true else
cb_output0.Checked
:= false; if
(convert.ToInt16(receivestring[8]) and
2) = 2 then
cb_output1.Checked
:= true else
cb_output1.Checked
:= false; end; if receivestring[1]
= 'i' then begin if
(convert.ToInt16(receivestring[7]) and
1) = 1 then
cb_input0.Checked
:= true else
cb_input0.Checked
:= false; if
(convert.ToInt16(receivestring[7]) 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
tb_counter0.Text :=
copy(ReceiveString, 10,length(ReceiveString)-10); if
copy(ReceiveString, 8, 1) = '1' then
tb_counter1.Text :=
copy(ReceiveString, 10,length(ReceiveString)-10); if
copy(ReceiveString, 8, 1) = ';' then begin
ReceiveString[8] :=
' ';
tb_counter0.Text :=
copy(ReceiveString, 9, pos(';',ReceiveString)-9);
tb_counter1.Text :=
copy(ReceiveString,
pos(';',ReceiveString)+1,
length(ReceiveString)-pos(';',ReceiveString)-1); end; end; end; end;
The Receive procedure uses the first character of the receive data to check whether these are input, output or counter messages. Depending on this, a determination is made for example as to which output has which status. With the counters it is possible both to query individual counter values as well as to read out all the counters at one time. The individual counter states are then output in decimal format in a semicolon delimited string.
5. 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
TWinForm.timer_polling_Tick1(sender: System.Object; e: System.EventArgs); begin if TCP_Client.Connected
then begin if cb_output_polling.Checked
then
sendcommand('GET
/output?PW=' + tb_password.Text + '&'); if cb_input_polling.Checked
then
sendcommand('GET
/input?PW=' + tb_password.Text + '&'); if cb_counter_polling.Checked
then
sendcommand('GET
/counter?PW=' + tb_password.Text + '&'); end; end;
The desired interval can be entered in the corresponding text field. When changes are made the timer interval is automatically adjusted.
procedure
TWinForm.tb_interval_TextChanged(sender: System.Object; e: System.EventArgs); begin
timer_polling.Interval := convert.ToInt16(tb_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. 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.
