I have a TCP server running which spits out messages of 2 bytes at regular intervals.
I'm trying to create a client side form which connects to the server and continuously reads from the stream until I click a disconnect button on the form.
So far the client works fine except that I cannot disconnect. I set the CancellationPending to true but it seems to reset back to false before the dowork method gets a chance to set e.Cancel.
I'm also sure there must be a more acceptable way of continuously reading the stream and writing to the form - at the moment I am calling RunWorkerAsync within the Worker Completed method to achieve the loop!
private void Disconnect()
{
commsWorker1.CancelAsync();
}
private void ReadFromStream()
{
try
{
commsWorker1.RunWorkerAsync();
}
catch (Exception ex)
{
writeToBox("Error: " + ex.Message);
}
}
//background worker dowork method
private void BackGroundGetServerData(object sender, DoWorkEventArgs e)
{
if (true == commsWorker1.CancellationPending)
{
e.Cancel = true;
}
else
{
Byte[] dataArray = new Byte[2];
try
{
_DataStream.Read(dataArray, 0, 2);
String reply = System.Text.Encoding.ASCII.GetString(dataArray);
e.Result = reply;
}
catch (Exception ex)
{
}
}
}
//background worker workercompleted method
private void BackGroundDisplayMessages(object sender, RunWorkerCompletedEventArgs e)
{
if (e.Cancelled)
{
//close connection here
}
else
{
writeToBox((String)e.Result);
commsWorker1.RunWorkerAsync();
}
}
}
}
Can't you just loop inside the background worker method?
private void BackGroundGetServerData(object sender, DoWorkEventArgs e)
{
while(true)
{
Byte[] dataArray = new Byte[2];
try
{
_DataStream.Read(dataArray, 0, 2);
String reply = System.Text.Encoding.ASCII.GetString(dataArray);
e.Result = reply;
}
catch (Exception ex)
{
return;
}
}
}
Then upon disconnect simply close the socket. This will cause the Exception
to be thrown in the while loop and you can exit gracefully through the catch
block.
Edit
: Then you can update the GUI from the loop after each message is read. Make sure the handle to the control you are updating is available (assuming it's called box
):
delegate void updateDelegate(String p);
private void BackGroundGetServerData(object sender, DoWorkEventArgs e)
{
while(true)
{
Byte[] dataArray = new Byte[2];
try
{
_DataStream.Read(dataArray, 0, 2);
String reply = System.Text.Encoding.ASCII.GetString(dataArray);
box.BeginInvoke(new updateDelegate(writeToBox), reply);
}
catch (Exception ex)
{
return;
}
}
}
BeginInvoke
is required in this case because you are trying to update the GUI from another thread, which is not allowed. This method forwards the update to the GUI thread.