监视连接到网络的客户端

Question

I have a requirement to monitor the client system connected to a LAN Network. If a system gets connected to a LAN , i need to get a notification and if a system gets disconnected from LAN, i need to get a notification.

Currently i am pinging the systems continuously in a C# code and getting the things done.

Drawbacks :-

1.I hard coded the system names to ping.

2.If the client is not reachable/ not in LAN / Host not found, the ping method waits for a period and throws exception.

3.So to to do this in Background, i perform this function in a thread.

4.Calling that thread inside a timer.

What is the best way to achieve this ?

ESSENCE

Some event , it should notify on new incoming connections, 
connection which is getting lost from LAN. This event should run async, monitor 
continuously.

I am using Windows Application (WPF) , C#.

Answer 1

Assuming you don't want to install an agent on all the PCs you want to monitor, the best thing to do would be to follow this process:

1. Look for any ARP Announce packet you receive. Add the IP address to the list of devices to monitor on the network and alert on it coming up.
2. Run a heartbeat on all IP addresses you have recorded.
   1. Perform a fast ping (Don't wait more than 10ms).
   2. If it doesn't respond, alert and remove it from the monitor list.