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Application to Debug Serial Port Communication

, 14 May 2007 CPOL
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This is a very simple app I use to test serial traffic. It enumerates the COM ports, allows you to edit all properties of SerialPort class instance. It also allows you to send files randomly to the serial port and save incoming data to a file.
Screenshot - Complay.jpg

Screenshot - Complay2.jpg


This is a very basic testing tool that I created to test my serial port handling code. I did Google for such a basic tool which you would think would exist, but...

A Few Things You Might Need

I bought a few cheap USB to serial port cables which are helpful for testing on one machine. You can also install emulated serial ports, but I'd rather go with a more real scenario for testing.

Basic Features

  1. The application allows you to send / receive data over the serial port and save it.
  2. It allows you to configure all options of the .NET SerialPort class with a propertyGrid.
  3. It allows you to select a directory and randomly send a file from that directory at a random interval.
  4. It enumerates the COM ports on your machine.

Using the Code

Almost all the functionality in the app is a one liner and completely self explanatory because .NET is such a well written high level language. The only tricky part of this app is that the serial port receives data on a separate thread. You cannot access visual controls from a separate thread, so you must invoke a delegate that will set the text and send a copy of the memory with (new object[] { text }).

It is important to notice that InvokeRequired will let you know if the thread ID is different.

What will happen when we receive data is, serialPort1_DataReceived handler will be fired when serial data is received and it will call SetText which is just a little wrapper that will in turn invoke the SetTextCallback delegate. The delegate is set to call SetText so SetText will be invoked again, but now it is on the UI thread. At this point, this.txtData.InvokeRequired will be false and we can set the text like we normally would.

// This delegate enables asynchronous calls for setting
// the text property on a TextBox control.
delegate void SetTextCallback(string text);
private void serialPort1_DataReceived
    (object sender, System.IO.Ports.SerialDataReceivedEventArgs e)

private void SetText(string text)
    // InvokeRequired required compares the thread ID of the
    // calling thread to the thread ID of the creating thread.
    // If these threads are different, it returns true.
    if (this.txtData.InvokeRequired)
        SetTextCallback d = new SetTextCallback(SetText);     
        this.Invoke(d, new object[] { text });
        this.txtData.Text = text;


The serial app I am testing deals with old data matrix printer drivers and so I'm dealing with strictly text data going through the port, which is probably not what most people are looking for. I realize it would be more generically useful if it had a binary editor built in.


  • 14th May, 2007: Initial post


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

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Comments and Discussions

Answerspecial thanks PinmemberHaresh Ambaliya25-Jan-11 11:45 
GeneralRe: special thanks Pinmemberrj4525-Jan-11 14:52 
Generalsmall application using serialport communication running on vista64 Pinmembermrdavidch15-Apr-09 9:30 
GeneralThanks! PinmemberDrew Loika14-Jul-08 16:18 
GeneralCarraige Return Pinmemberkamarchand21-May-08 10:15 
GeneralRe: Carraige Return Pinmemberrj4521-May-08 10:47 
GeneralSend ascii Pinmemberrj4511-Sep-07 12:33 
QuestionThanks for the awesome article PinmemberAmarjeetSinghMatharu21-Aug-07 18:22 
QuestionHow to turn off the DataReceived Event in SerialPort class PinmemberAmarjeetSinghMatharu10-Sep-07 1:25 
AnswerRe: How to turn off the DataReceived Event in SerialPort class PinmemberAgnius Vasiliauskas27-Nov-07 4:12 
Questionreceive binary data and save it in binary file PinmemberMauricioPrincipi23-Jul-07 5:33 
GeneralClosing the port Pinmemberjasperp21-May-07 20:58 
GeneralRe: Closing the port Pinmemberrj4522-May-07 8:46 
GeneralRe: Closing the port - Doesn't this work with Virtual ports? PinmemberVijay Chandra Sekhar Parepalli15-Dec-09 17:50 
GeneralRe: Closing the port - Doesn't this work with Virtual ports? Pinmemberrj4516-Dec-09 6:57 
GeneralRe: Closing the port Pinmemberrj4522-May-07 8:55 
QuestionRe: Closing the port - App Hangs PinmemberPaglia24-Oct-07 2:35 
GeneralSending Reciving Binary file Pinmembertarikthecoder20-May-07 0:42 
GeneralRe: Sending Reciving Binary file Pinmemberrj4522-May-07 8:49 
GeneralRe: Sending using write function in serial port Pinmemberpallaka29-Aug-09 2:29 
GeneralRe: Sending using write function in serial port Pinmemberrj4531-Aug-09 10:25 
GeneralGood job PinmemberThe Code Guru14-May-07 22:18 
GeneralNice PinmemberStuart Dootson14-May-07 22:10 
GeneralCan't get it running with VSPD XP4. PinmemberBartosz Bien14-May-07 23:03 
GeneralRe: Can't get it running with VSPD XP4. Pinmemberrj4515-May-07 9:17 

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