Control and monitor the Web-IO Digital with Visual C#

Visual C++ was until recently one of the most widely used development platforms for creating Windows applications. But in the meantime, more and more programmers are working with the .Net Framework and creating their applications in C#.

Using the following C# 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.

• with power,
• configured the inputs and outputs,
• connected it to your network,
• assigned it an IP address - which with WuTility is no problem.

• Firstly, all classes required for the network connection and the GUI are imported.
  

  	using System; using System.Drawing; using System.Collections; using System.ComponentModel; using System.Windows.Forms; using System.Data; using System.Net; using System.Net.Sockets; using System.Text;

  
  
• Then the application components and important variables for a TCP connection are declared as member variables, thereby making them accessible to the class methods.
  
  

  private System.Windows.Forms.CheckBox cb_Output0; private System.Windows.Forms.CheckBox cb_Output1; private System.Windows.Forms.CheckBox cb_Input0; private System.Windows.Forms.CheckBox cb_Input1; private System.Windows.Forms.CheckBox cb_Polling_Counter; private System.Windows.Forms.CheckBox cb_Polling_Outputs; private System.Windows.Forms.CheckBox cb_Polling_Inputs; private System.Windows.Forms.Button bt_Readall_Outputs; private System.Windows.Forms.Button bt_Readall_Inputs; private System.Windows.Forms.Button bt_Clear_Counter0; private System.Windows.Forms.Button bt_Clear_Counter1; private System.Windows.Forms.Button bt_Clearall_Counter; private System.Windows.Forms.Button bt_Read_Counter0; private System.Windows.Forms.Button bt_Read_Counter1; private System.Windows.Forms.Button bt_Readall_Counter; private System.Windows.Forms.Label lb_Counter0; private System.Windows.Forms.Label lb_Counter1; private System.Windows.Forms.Label lb_Intervall; private System.Windows.Forms.TextBox tb_Counter0; private System.Windows.Forms.TextBox tb_Counter1; private System.Windows.Forms.TextBox tb_Intervall; private System.Windows.Forms.Button bt_Connect; private System.Windows.Forms.Button bt_Disconnect; private System.Windows.Forms.TextBox tb_Password; private System.Windows.Forms.TextBox tb_Port; private System.Windows.Forms.TextBox tb_IP; private System.Windows.Forms.GroupBox gb_ioControlBox; private System.Windows.Forms.GroupBox gb_conControlBox; private System.Windows.Forms.StatusBar statusBar; private System.ComponentModel.Container components = null; private System.Windows.Forms.Timer counter; private System.Windows.Forms.Timer outputs; private System.Windows.Forms.Timer inputs; private Socket client; private string rcv; private int intervall; private byte[] buffer = new byte[256];

• Setting up the operating elements
  The group with the operating elements for the Web-IO is first blocked from operation. As soon as a connection is established, all elements are enabled which have a meaningful format.
  
  
• The name of the respective operating element is derived from the element itself depending on the context. The first two characters in the name stand for the element type (cb -> Checkbox, bt -> Button, gb -> Groupbox and
  tb-> TextBox).
  
  

• Establishing the connection
  After entering the IP address for the Web-IO in the text field tb_IP and Port 80 in the text field tb_port, clicking on the bt_connect button allows a connection to be opened. If no IP address or port is entered, a message is displayed in the status bar
  
  
• Opening the connection
  Now to be able to open a TCP connection, the already declared socket variable is initialized. It is given a stream and the connection type. In addition, a variable is generated which saves the port and IP address.
  
  So that the program can run asynchronous, it does not wait for events, but rather uses callback routines. Callback methods are initialized when a process is started and invoked when the corresponding event occurs, i.e. for example when a connection is opened, for sending or receiving.

• In the following the callback routine is shown which is invoked when the connection is established.
  After successfully opening a connection, all useful operating elements for the application are enabled and the Connect button deactivated. In addition, the application immediately begins to go into receive ready mode. For this the callback routine "receivecallback" is initialized, which is explained in greater detail below.

• Disconnecting
  The connection remains open until the user clicks on the Disconnect button or until it is ended by the Web-IO. After clicking on the button a message is displayed that the connection has been ended.

• When the connection is ended all elements must be returned to their initial state. It should then no longer be possible to actuate the Disconnect button.

• Now the connection is closed again and the application reset to its initial state.

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.

• When sending a message to the Web-IO, a callback routine is invoked just as in the case of receiving.
  
  
  

  	private void sendCallback(IAsyncResult ar) {   try   {     Socket tmp_client = (Socket) ar.AsyncState;     int bytessend = tmp_client.EndSend(ar);   }   catch(Exception)   { statusBar.Text = "Error while sending"; } }

  
  
• Setting the outputs
  The outputs on the Web-IO can be switched using the two checkboxes IDC_OUTPUT0 and IDC_OUTPUT1. The checkbox notes when it was clicked and then triggers an action. Depending on whether the checkbox is already set, the output is either set to ON or OFF.

• Query output/input status

• Query counters
  The following method sends a request to a particular counter and requests a reply containing the current state of the counter.
  

• Of course all the counter states can also be polled using one command.
  
  

  	private void bt_Readall_Counter_Click(object sender, System.EventArgs e) {   send("GET /counter?PW=" + tb_Password.Text + "&"); }

  
  
• Reset counter
  

• Of course all the counters can be reset together using a single command.
  
  

  	private void bt_Clearall_Counter_Click(object sender, System.EventArgs e) {   send("GET /counterclear?PW=" + tb_Password.Text + "&"); }

  
  
• Since all counter states can be read or reset using one command, there must be a method implemented which processes the reply string from the Web-IO and assigns each counter in the application its specific state.
  
  

  	private void readAndClearCounter(string data) {   int j = 0;   string[] counter = new string[12];   for(int i = 0; i < data.Length-1; i++)   {     if((data[i].CompareTo(';')) == 0)       j++;     else       counter[j] += data[i].ToString();   }   tb_Counter0.Text = counter[0];   tb_Counter1.Text = counter[1]; }

• 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 a special output: outputx;<ON or OFF>
  
  For the inputs: input;<binary value of the input status in hexadecimal format>
  For a special input inputx;<ON or OFF>
  
  Then there is the reply string for a counter, which looks as follows.
  
  Counter: counterx;<decimal counter state>
  
  or counter;<decimal counter state 0 >; <decimal counter state 0 >; ... if you want to read all the counters at one time.
  
  All reply strings are finished off with a 0 byte.
  
  In our application the method receiveCallback() is invoked to receive such a message. In this method the reply string from the Web-IO is read and processed. The unique feature here is the event-driven invoking, which takes place as soon as the Web-IO sends data to the application.

• Cyclical polling of particular values
  It is desirable that the status of an individual component be updated by the component itself, so that the application always shows the current status. For this the program uses a timer which sends cyclical queries to the Web-IO at a user-defined time interval.
  
  The time interval can be specified in the field IDC_POLLINGTEXT.
  
  Of course this also catches cases where the user enters a nonsense value, such as a negative time value.

• To carry out cyclical polling of the Web-IO states, you can select from among polling the outputs, the inputs or the counters.
  
  Each polling variant has its own timer initialized.
  
  Actuating the checkbox cb_Polling_Outputs causes polling to be applied to the outputs. The corresponding timer is initialized.

• The same applies to inputs and counters

• In this method the respective event of the time which is currently reporting is captured and assigned to a particular action.