CheckIfPortIsAvailable C#

CheckIfPortIsAvailable.cs

using System;
using System.Net;
using System.Net.Sockets;

public class CheckIfPortIsAvailable {
    public static bool IsAvailable(int portNumber) {
        var localhost = (IPAddress) Dns.GetHostAddresses("localhost")[0];

        try {
            var sock = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            sock.Connect(localhost, portNumber);
            if (sock.Connected == true)  // Port is in use and connection is successful
                return false;
            else
                throw new Exception("Not connected to port ... but no Exception was thrown?");
        } catch (SocketException ex) {
            if (ex.ErrorCode == 10061)  // Port is unused and could not establish connection 
                return true;
            else
                throw ex;
        }
    }

    public static void Main(string[] args) {
        var port      = int.Parse(args[0]);
        var available = IsAvailable(port);

        if (available)
            Console.WriteLine("Port {0} is available", port);
        else
            Console.WriteLine("Port {0} is NOT available", port);
    }
}