private void SlidingWindow(TimeSpan tsSend_Time, bool bIsGoBackN)
{
object[] arr_Frames = Q_Frames.ToArray();
if (Q_Frames.Count != 0)//Sending Frames
{
objFrame.Fxpos += fspeed * objFrame.Fvec_X;
lbl_sender.Text = "Sending " + arr_Frames[0].ToString();
lbl_receiver.Text = "Receiving " + arr_Frames[0].ToString();
if (objFrame.Fxpos + dlen > nwidth)//frame reached Rx
{
object Objreceivedframe = Q_Frames.Dequeue();
if (tsSend_Time.Seconds < dtimeout) //within time
{
if (bcontinue_receive) //sending was not interrupted,receive frames normally
{
LBx_Receiver.Items.Add(Objreceivedframe);
LBx_Log.Items.Add(Objreceivedframe.ToString() + " received");
Q_Acks.Enqueue(Objreceivedframe);
objAck = new clssSqaure(nwidth, -20, -1, color_yellow);//Send Ack
lst_clssSqaure.Add(objAck);
}
}
else//frame exceeded time
{
LBx_Log.Items.Add(Objreceivedframe.ToString() + " timed out");
if (bIsGoBackN && bcontinue_receive)
{
LBx_Log.Items.Add("Rx stopped receiving");
bcontinue_receive = false;//stop receiving
}
}
dtstart = DateTime.Now; //reset time
objFrame.Fxpos = 10 - nwidth; //reset Frame position
}
}
if (Q_Acks.Count != 0)//Sending Ack
{
objAck.Fxpos += fspeed * 2 * objAck.Fvec_X;
if (((objAck.Fxpos - dlen + 10) < (nwidth * -1)))//Ack arrived to Tx
{
LBx_Log.Items.Add("Ack received");
LBx_Sender.Items.Remove(Q_Acks.Dequeue());
lst_clssSqaure.Remove(objAck);
}
}
if (Q_Frames.Count == 0 && Q_Acks.Count == 0)
{
lbl_receiver.Text = lbl_sender.Text = "Ready";
lbl_TimeElapsed.Text = string.Empty;
}
}
private void btn_Send_Click(object sender, EventArgs e)
{
#region Initialization
lst_clssSqaure.Clear();
objFrame = new clssSqaure(10 - nwidth, 20, 1, color_Blue);
lst_clssSqaure.Add(objFrame);
bsend_file = true;
dtstart = DateTime.Now;
if (txt_Timeout.Text != string.Empty)
{
dtimeout = int.Parse(txt_Timeout.Text);
}
else
{
dtimeout = 3;//default value
}
#endregion
if (rb_stp_wait.Checked)
{
if (LBx_Sender.SelectedIndex < 0)
{
MessageBox.Show("please select frame to send", "Info", MessageBoxButtons.OK, MessageBoxIcon.Warning);
return;
}
objselected_frame_stp_wt = LBx_Sender.SelectedItem;
}
else
{
if (!bcontinue_receive)
{
bcontinue_receive = true;
}
//modify window size to the count of remaining items
nwin_size = Convert.ToInt32(num_win_size.Value);
if (nwin_size > LBx_Sender.Items.Count)
{
nwin_size = LBx_Sender.Items.Count;
}
for (int i = 0; i < nwin_size; i++)
{
Q_Frames.Enqueue(LBx_Sender.Items[i]);
}
}
timer1.Enabled = simpleOpenGlControl1.Visible = true;
}
private void transform()
{
TimeSpan tsSend_Time = DateTime.Now - dtstart;
lbl_TimeElapsed.Text = tsSend_Time.ToString();
if (rb_stp_wait.Checked)
{
#region Stop & Wait
#region Explanation
/*
* Stop after Transmitting a Frame
* Wait for an Acknowledgement
*
*
* Tx Rx
*
* Frame_0
* |------------------->|
* | |
* | Ack|
* |<-------------------|
* | |
* | |
* |Frame_1 |
* |----------> |
* | Timeout|
* | NAck|
* |<-------------------|
* | |
* | |
* Frame_2
* |------------------->|
* | |
* | Ack|
* | <----------|
* | |
* |Timeout |
*/
#endregion
if (objselected_frame_stp_wt != null)
{
if (tsSend_Time.Seconds > dtimeout) //send time exceeded predetermined timeout
{
if (bsend_file) //Rx didnt receive Frame
{
lbl_receiver.Text = "Timeout";
}
else //Tx didnt receive Acknowledgment
{
lbl_sender.Text = "Timeout";
}
timer1.Enabled = false;//stop sending
}
if (bsend_file)//Frame is being sent to Rx
{
if (LBx_Receiver.Items.Contains(objselected_frame_stp_wt))
{
lbl_sender.Text = "Resending " + objselected_frame_stp_wt.ToString();
}
else
{
lbl_sender.Text = "Sending " + objselected_frame_stp_wt.ToString();
}
if ((objFrame.Fxpos + dlen) > nwidth)//frame arrived to Rx
{
if (!LBx_Receiver.Items.Contains(objselected_frame_stp_wt))
{
LBx_Receiver.Items.Add(objselected_frame_stp_wt);
}
lbl_sender.Text = "awaiting acknowledgement";
lbl_receiver.Text = "sending acknowledgement";
bsend_file = false;
dtstart = DateTime.Now;
objAck = new clssSqaure(nwidth, -20, -1, color_yellow);
lst_clssSqaure.Add(objAck);
}
objFrame.Fxpos += fspeed * objFrame.Fvec_X;
}
else//Ack is being sent to Tx
{
if (((objAck.Fxpos - dlen + 10) < (nwidth * -1)))//Ack arrived to Tx
{
lbl_sender.Text = "Acknowledgement received";
if (LBx_Receiver.Items.Contains(objselected_frame_stp_wt))
{
LBx_Sender.Items.Remove(objselected_frame_stp_wt);
}
timer1.Enabled = false;
bsend_file = true;
}
objAck.Fxpos += fspeed * objAck.Fvec_X;
}
}
#endregion
}
else if (rb_goback_N.Checked)
{
#region Go Back N
#region Explanation
/*
* the sending process continues to send a number of frames specified by
* a window size without waiting for the ACK packet from the receiver.
*
* if any frame was lost or damaged, or the ACK acknowledging them was lost or damaged,
* then that frame and all following frames in the window
* (even if they were received without error) will be re-sent.
*/
#endregion
SlidingWindow(tsSend_Time, true /*Is it GoBackN*/);
#endregion
}
else
{
#region Selective Repeat
#region Explanation
/* The sending process continues to send a number of frames specified by a window size even after a frame loss.
* Unlike Go-Back-N ARQ, the receiving process will continue to accept and acknowledge frames sent after an initial
* error.
* Only faulted frames will be resent.
* */
#endregion
SlidingWindow(tsSend_Time, false /*Is it GoBackN*/);
#endregion
}
}
