SocketException Connection failed

SocketException Connection failed

I use the sample code on MSDN but it cannot work.
Below is code:
IPHostEntry ipHost = Dns.GetHostEntry(Dns.GetHostName());
IPAddress ipAddr = ipHost.AddressList[2];
IPEndPoint ipEndPoint = new IPEndPoint(ipAddr, 11000);
Socket client = new Socket(AddressFamily.InterNetwork, SocketType.Stream,
ProtocolType.Tcp);
client.Connect(ipEndPoint);