(转)用C#实现实现简单的 Ping 的功能，用于测试网络是否已经连通

 /// <summary>
        /// 根据IP地址获得主机名称
        /// </summary>
        /// <param name="ip">主机的IP地址</param>
        /// <returns>主机名称</returns>
        public string GetHostNameByIp(string ip)
        {
            ip = ip.Trim();
            if (ip == string.Empty)
                return string.Empty;
            try
            {
                // 是否 Ping 的通
                if (this.Ping(ip))
                {
                    System.Net.IPHostEntry host = System.Net.Dns.GetHostEntry(ip);
                    return host.HostName;
                }
                else
                    return string.Empty;
            }
            catch (Exception)
            {
                return string.Empty;
            }
        }

 /// <summary>
        /// 根据主机名（域名）获得主机的IP地址
        /// </summary>
        /// <param name="hostName">主机名或域名</param>
        /// <example> GetIPByDomain("www.google.com");</example>
        /// <returns>主机的IP地址</returns>
        public string GetIpByHostName(string hostName)
        {
            hostName = hostName.Trim();
            if (hostName == string.Empty)
                return string.Empty;
            try
            {
                System.Net.IPHostEntry host = System.Net.Dns.GetHostEntry(hostName);
                return host.AddressList.GetValue(0).ToString();
            }
            catch (Exception)
            {
                return string.Empty;
            }
        }

/// <summary>
        /// 是否能 Ping 通指定的主机
        /// </summary>
        /// <param name="ip">ip 地址或主机名或域名</param>
        /// <returns>true 通，false 不通</returns>
        public bool Ping(string ip)
        {
            System.Net.NetworkInformation.Ping p = new System.Net.NetworkInformation.Ping();
            System.Net.NetworkInformation.PingOptions options = new System.Net.NetworkInformation.PingOptions();
            options.DontFragment = true;
            string data = "Test Data!";
            byte[] buffer = Encoding.ASCII.GetBytes(data);
            int timeout = 1000; // Timeout 时间，单位：毫秒
            System.Net.NetworkInformation.PingReply reply = p.Send(ip, timeout, buffer, options);
            if (reply.Status == System.Net.NetworkInformation.IPStatus.Success)
                return true;
            else
                return false;
        }

private void button1_Click(object sender, EventArgs e)//获取IP
        { textBox2.Text=GetIpByHostName(textBox1.Text);   }
  private void button2_Click(object sender, EventArgs e)//获取主机名
        {  textBox1.Text=GetHostNameByIp(textBox2.Text);   }
   private void button3_Click(object sender, EventArgs e)//获取本机IP
        {
            string hostName = System.Net.Dns.GetHostName();
            IPHostEntry ipEntry = System.Net.Dns.GetHostEntry(hostName);
            //Dns.GetHostByName(myName);已过时
            IPAddress[] addr = ipEntry.AddressList;
            textBox2.Text = addr[0].ToString();
        }
        /// <summary>
        /// 局域网搜索事件
        /// </summary>
        private void LanSearch()
        {
string localhost = (Dns.GetHostEntry(Dns.GetHostName()))
.AddressList[0].ToString(); //本地主机IP地址
            string str = localhost.Substring(0, localhost.LastIndexOf("."));
            for (int i = 0; i < 255; i++) //建立255个线程扫描IP
            {
                string ip = str + "." + i.ToString();
                this.Text  = ip;
                if (Ping(ip))
                {
                    listBox1.Items.Add(ip);                       
                    Application.DoEvents(); 
                }
                progressBarSearch.Value = progressBarSearch.Value + 1;
            }
        }
        private void button4_Click(object sender, EventArgs e)//在线主机
        {
            LanSearch();
        }