Thanks a lot for your help. I find them really useful in carrying on my work. My concern was to create a program that can trigger an alert when one of the server is down (I mean the network connection). And the action of the alert is to send SMS. I hope I can implement those code you recommended

But now I really face a difficult problem. Below is my company's server network (the ISA server, I'm thinking, should be placed before the switch)
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ISA Server
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Switch
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server server server server


All the IP addresses of the servers are public addresses (and belong to class C, default subnet mask). Thus my ISA Server needs to have 2 network adapters in order to connect to the switch and to the external devices (in this case, the router). Thus, if the 2 IP addresses on the ISA Server computer belong to the same subnet (in my case, this is a class C, default subnet 255.255.255.0), I don't know if the ISA Server can work well with the functions of a firewall, monitoring, alerting... And I am not sure if my colleagues can do the remote control to the servers through the ISA server computer.
In this case, the ISA Server works like a router. But a router has its ip addresses which belong to different subnets. Because usually I know that the 2 IP addresses of the 2 sides of a device should be in different subnets.
So, do you have any comments
Please help. I'm really stressful to come up with the final design so that the real implementation can be done as soon as possible