C#实现简单的 Ping 的功能，用于测试网络是否已经联通

  /// <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 = ; // 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;
          }

http://www.cnblogs.com/anjou/archive/2007/10/11/920214.html