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, 3 Apr 2012 CPOL
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Blinks keyboard LEDs to display network traffic.


I wanted to see the network activity other than in the system tray network icon, so I thought of using the keyboard's CAPS LOCK, SCROLL LOCK, and NUM key LEDs to display the network activity. TrafficLights is a simple application which blinks keyboard lights based on the network traffic on your computer. You can configure which light should blink on send or receive packets. It silently sits on your system tray. You can right click on TrafficLights' system tray icon to configure the LEDs or shut it down.


This is just to learn how to trap network traffic and control keyboard LEDs in .NET.

Using the Code

There are basically two parts to this application:

  • How to identify network traffic.
  • The code below is used to initialize the PerformanceCounter class instances - one for send and one for receive (namely m_performanceCounterSent and m_performanceCounterReceive). They are initialized like so:

    m_performanceCounterCategory = new PerformanceCounterCategory("Network Interface");
    string instance = m_performanceCounterCategory.GetInstanceNames()[0]; // 1st NIC !
    m_performanceCounterSent = new PerformanceCounter("Network Interface", 
                                   "Bytes Sent/sec", instance);
    m_performanceCounterReceived = new PerformanceCounter("Network Interface", 
                                       "Bytes Received/sec", instance);
  • How to control keyboard LEDs.
  • A background thread keeps running in the application, and it keeps on checking on the performance counter to check any network activity. And when an activity is detected, it blinks the configured keyboard LED.

    float fSentValue = m_performanceCounterSent.NextValue() / 1024;
    float fReceivedValue = m_performanceCounterReceived.NextValue() / 1024;
    if (fSentValue > 0)
       keybd_event((byte)m_sendLED, 0x45, KEYEVENTF_EXTENDEDKEY, (UIntPtr)0);
       keybd_event((byte)m_sendLED, 0x45, 
    if (fReceivedValue > 0)
       keybd_event((byte)m_receiveLED, 0x45, KEYEVENTF_EXTENDEDKEY, (UIntPtr)0);
       keybd_event((byte)m_receiveLED, 0x45, 

Points of Interest

As I mentioned earlier, it's a very simple application, but the intention was to learn how to trap network traffic in .NET.


This is the first version of this application. Also, my first attempt to post anything on CodeProject.


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


About the Author

Amit Engineer

United States United States
No Biography provided

Comments and Discussions

QuestionNot sure it's a good idea. PinmemberMember 30824879-Apr-12 23:03 
QuestionStart menu PinmemberAndreasJoh4-Apr-12 3:01 
GeneralMy vote of 5 PinmemberAbinash Bishoyi22-Mar-12 2:32 
GeneralGood C# copy PinmemberIgor Tolmachev16-Jan-10 5:53 
GeneralRe: Good C# copy PinmemberAmit Engineer18-Jan-10 10:01 
GeneralRe: Good C# copy Pinmembertkrafael_net3-Apr-12 12:47 
GeneralNice and funny PinmemberMuhammad Nauman Yousuf14-Dec-09 23:24 
GeneralNice but heavy CPU load PinmemberThomas Kuehn11-Dec-09 9:38 
GeneralRe: Nice but heavy CPU load PinmemberAmit Engineer11-Dec-09 11:01 
Ohhh, with my dual core I did not notice it and did not realize it. Will make changes.


QuestionRe: Nice but heavy CPU load PinmemberAmit Engineer11-Dec-09 11:11 
AnswerRe: Nice but heavy CPU load PinmemberIgor Tolmachev16-Jan-10 5:56 
Generalgreat Pinmemberthebeekeeper11-Dec-09 5:57 
Generalfunny.. [modified] Pinmemberreborn_zhang11-Dec-09 5:45 
GeneralRe: funny.. Pinmemberreborn_zhang11-Dec-09 5:56 

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