What have you written so far?

try writing some pseudo code first

you will want an IP

and a specific range of ports to check.

you will need a method for sending a ping to them and a method for listening for a response (three part handshake for networking peeps)

you should start by writing something that can ping a local address, or even just something that can connect to a local machine to get the feel for how networking works.

Could You give me a little example(C#), so i`ll try to continue
Thanks

you should really try to gain an understanding of what you are trying to do.

in about 30 seconds of google searching i was able to find examples of what you need to do.

hint an IP with a PORT is called a socket

so look up C# and sockets.

Ok
I`ll try to ask accurate question:
I need to implement few type of scanning:
- TCP connect()
- TCP SYN scan
- TCP FIN scan
- TCP XMAS scan
- TCP NULL scan

I already did something:

public static void connect1(string host, int startPort, int finishPort)
{

IPAddress[] IPs = Dns.GetHostAddresses(host);
Socket s = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
Console.WriteLine("Establishing Connection to {0}", host);

for (int curPort = startPort; curPort <= finishPort; curPort++)
{

try
{
s.Connect(IPs[0], curPort);
Console.WriteLine("Port {0} : opened", curPort);
}
catch
{
Console.WriteLine("Port {0} : blocked", curPort);
}
}

It`s working, but I don`t know which type is it, and how to continue
with other types
Thanks