Tn events are specially important in asynchronous programming. A typical case is a custom terminal emulator, where the screens and state info must be reflected in the user interface.

The Tn events are:

 OnConnect                : Fires after a successfully connection to the mainframe is established.

 OnConnectFail        : Fires after the connection to the mainframe fails.

 OnDisconnect        : Fires after a disconnection with the mainframe.

 OnSessionState        : Fires when a session-state change takes place.        

 OnSystemLock        : Fires when a terminal changes to a system locked state.

 OnSystemUnLock        : Fires when a terminal changes to a system unlocked state.

 OnScreenChange        : Fires after a new data screen has arrived.

 OnSendAid                : Fires when an AID key is about to be sent (before is sent).

Some code examples:

 VB.NET:

 Private Sub tn3270_OnConnect(eventSender As System.Object, eventArgs As System.EventArgs)

    MessageBox.Show("Connected to the Host!");

 End Sub

 Private Sub tn3270_OnConnectionFail(eventSender As System.Object, eventArgs As System.EventArgs)

    MessageBox.Show("Connection Failed!");

 End Sub

 Private Sub tn3270_OnDisconnect(eventSender As System.Object, eventArgs As System.EventArgs)

    MessageBox.Show("Disconnected from the Host!");

 End Sub

 C#:

 private void tn3270_OnConnect(object eventSender, System.EventArgs eventArgs)

 {

    MessageBox.Show("Connected to the Host!");

 }

 private void tn3270_OnConnectionFail(object eventSender, System.EventArgs eventArgs)

 {

    MessageBox.Show("Connection Failed!");

 }

 private void tn3270_OnDisconnect(object eventSender, System.EventArgs eventArgs)

 {

    MessageBox.Show("Disconnected from the Host!");

 }

 VB.NET:

 Private Sub tn3270_OnScreenChange(eventSender As System.Object, eventArgs As System.EventArgs)

    MessageBox.Show("A new screen has been received");

 End Sub

 Private Sub tn3270_OnSystemUnLock(eventSender As System.Object, eventArgs As System.EventArgs)

    MessageBox.Show("The latest screen has arrived");

 End Sub

 C#:

 private void tn3270_OnScreenChange(object eventSender, System.EventArgs eventArgs)

 {

    MessageBox.Show("A new screen has been received");

 }

 private void tn3270_OnSystemUnLock(object eventSender, System.EventArgs eventArgs)

 {

    MessageBox.Show("The latest screen has arrived");

 }

 VB.NET:

 Private Sub tn3270_OnSystemUnLock(eventSender As System.Object, eventArgs As System.EventArgs)

    MessageBox.Show("We can send data to the host now");

 End Sub

 Private Sub tn3270_OnSystemLock(eventSender As System.Object, eventArgs As System.EventArgs)

    MessageBox.Show("We can''t send data at this moment!");

 End Sub

 C#:

 private void tn3270_OnSystemUnLock(object eventSender, System.EventArgs eventArgs)

 {

    MessageBox.Show("We can send data to the host now");

 }

 private void tn3270_OnSystemLock(object eventSender, System.EventArgs eventArgs)

 {

    MessageBox.Show("We can''t send data at this moment!");

 }

 VB.NET:

 Private Sub tn3270_OnSystemUnLock(eventSender As System.Object, eventArgs As System.EventArgs)

    'At this time we can send data to the host

    'First we check if we are in the log-on screen

  If (tn3270.GetText(15,1,tn3270.Cols).Substring(10,8) = "UserId:") Then

     'Now we fill in the input fields

    tn3270.EditFields[0].Data = "MyUserId"

    tn3270.EditFields[1].Data = "MyPasword"

     'and send them to the host with the Enter Key!

    tn3270.Press(Enter)

        Else If

    ...

        End If

 End Sub

 C#:

 private void tnb3270_OnSystemUnLock(object sender, System.EventArgs e)

 {

    // At this time we can send data to the host

    // First we check if we are in the log-on screen

  if (tn3270.GetText(15,1,tn3270.Cols).Substring(10,8) = "UserId:")

   {

     // Now we fill in the input fields

    tn3270.EditFields[0].Data = "MyUserId";

    tn3270.EditFields[1].Data = "MyPasword";

     // and send them to the host with the Enter Key!

    tn3270.Press(Enter);

   }

  else

   {

         ...

   }

 }