使用InternetGetConnectedState判断本地网络状态（C#举例）

函数原型：函数InternetGetConnectedState返回本地系统的网络连接状态。

语法：

BOOL InternetGetConnectedState(

__out LPDWORD lpdwFlags,

__in DWORD dwReserved

);

参数：

lpdwFlags[out]

指向一个变量，该变量接收连接描述内容。该参数在函数返回FLASE时仍可以返回一个有效的标记。该参数可以为下列值的一个或多个

值	含义
INTERNET_CONNECTION_CONFIGURED   0x40(64)	Local system has a valid connection to the Internet, but it might or might not be currently connected.
INTERNET_CONNECTION_LAN                   0x02(2)	Local system uses a local area network to connect to the Internet.
INTERNET_CONNECTION_MODEM0             x01(1)	Local system uses a modem to connect to the Internet.
INTERNET_CONNECTION_MODEM_BUSY0   x08(8)	No longer used.
INTERNET_CONNECTION_OFFLINE             0x20(16)	Local system is in offline mode.
INTERNET_CONNECTION_PROXY                0x04(4)	Local system uses a proxy server to connect to the Internet.
INTERNET_RAS_INSTALLED                        0x10(8)	Local system has RAS installed.

dwReserved[in]

保留值。必须为0。

当存在一个modem或一个LAN连接时，返回TRUE，当不存在internet连接或所有的连接当前未被激活时，返回false。

当该函数返回false时，程序可以调用GetLastError来接收错误代码。

运行效果：

代码：

using System;
using System.Collections.Generic;
using System.Text;
using System.Net.NetworkInformation;

namespace ConsoleApplication1
{
    class Program
    {
        public static void Main(string[] args)
        {
            string url = "www.baidu.com;www.sina.com;www.cnblogs.com;www.google.com;www.163.com;www.csdn.com";
            string[] urls = url.Split(new char[] { ';' });
            CheckServeStatus(urls);

            Console.ReadKey();
        }
        
        /// <summary>
        /// 检测网络连接状态
        /// </summary>
        /// <param name="urls"></param>
        public static void CheckServeStatus(string[] urls)
        {
            int errCount = 0;//ping时连接失败个数

            if (!LocalConnectionStatus())
            {
                Console.WriteLine("网络异常~无连接");
            }
            else if (!MyPing(urls, out errCount))
            {
                if ((double)errCount / urls.Length >= 0.3)
                {
                    Console.WriteLine("网络异常~连接多次无响应");
                }
                else
                {
                    Console.WriteLine("网络不稳定");
                }
            }
            else
            {
                Console.WriteLine("网络正常");
            }
        }

        #region 网络检测

         private const int INTERNET_CONNECTION_MODEM = 1;
        private const int INTERNET_CONNECTION_LAN = 2;

        [System.Runtime.InteropServices.DllImport("winInet.dll")]
        private static extern bool InternetGetConnectedState(ref int dwFlag, int dwReserved);

        /// <summary>
        /// 判断本地的连接状态
         /// </summary>
        /// <returns></returns>
        private static bool LocalConnectionStatus()
        {
            System.Int32 dwFlag = new Int32();
            if (!InternetGetConnectedState(ref dwFlag, 0))
            {
                Console.WriteLine("LocalConnectionStatus--未连网!");
                return false;
            }
            else
            {
                if ((dwFlag & INTERNET_CONNECTION_MODEM) != 0)
                {
                    Console.WriteLine("LocalConnectionStatus--采用调制解调器上网。");
                    return true;
                }
                else if ((dwFlag & INTERNET_CONNECTION_LAN) != 0)
                {
                    Console.WriteLine("LocalConnectionStatus--采用网卡上网。");
                    return true;
                }
            }
            return false;
        }

        /// <summary>
        /// Ping命令检测网络是否畅通
        /// </summary>
        /// <param name="urls">URL数据</param>
        /// <param name="errorCount">ping时连接失败个数</param>
        /// <returns></returns>
        public static bool MyPing(string[] urls, out int errorCount)
        {
            bool isconn = true;
            Ping ping = new Ping();
            errorCount = 0;
            try
            {
                PingReply pr;
                for (int i = 0; i < urls.Length; i++)
                {
                    pr = ping.Send(urls[i]);
                    if (pr.Status != IPStatus.Success)
                    {
                        isconn = false;
                        errorCount++;
                    }
                    Console.WriteLine("Ping " + urls[i] + "    " + pr.Status.ToString());
                }
            }
            catch
            {
                isconn = false;
                errorCount = urls.Length;
            }
            //if (errorCount > 0 && errorCount < 3)
            //  isconn = true;
            return isconn;
        }

        #endregion
    }
}