using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Linq;using System.Net;using System.Net.Sockets;using System.Text;using System.Threading.Tasks;using System.Windows.Forms;namespace 扫描计算机的端口号{    public partial class Form1 : Form    {        public Form1()        {            InitializeComponent();        }        private void button1_Click(object sender, EventArgs e)        {            listBox1.Items.Clear();            if (string.IsNullOrEmpty(textBox1.Text.Trim())||string.IsNullOrEmpty(textBox2.Text.Trim())||string.IsNullOrEmpty(textBox3.Text.Trim()))            {                MessageBox.Show("输入端口号和IP地址。。。","提示");                return;            }            IPAddress ip = IPAddress.Parse(textBox3.Text.Trim());//通过IP字符串实例化IPAddress类            for (int i =Convert.ToInt32(textBox1.Text); i < Convert.ToInt32(textBox2.Text)+1; i++)            {                TcpClient tx = new TcpClient();//实例化                try                {                    tx.Connect(ip, i);//使用IP地址和端口号连接主机。                    listBox1.Items.Add("COM：" + i + "是开放的.");                }                catch { }                 finally {tx.Close();//释放该实例，但不关闭基础连接。}                               }            listBox1.Items.Add("扫描结束！");        }    }}