使用InternetGetConnectedState判斷本地網絡狀態（C#舉例）

函數原型：函數InternetGetConnectedState返回本地系統的網絡連接狀態。

語法：

BOOL InternetGetConnectedState(

__out LPDWORD lpdwFlags,

__in DWORD dwReserved

);

參數：

lpdwFlags[out]

指向一個變量，該變量接收連接描述內容。該參數在函數返回FLASE時仍可以返回一個有效的標記。該參數可以為下列值的一個或多個

值	含義
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。必須為0。

當存在一個modem或一個LAN連接時，返回TRUE，當不存在internet連接或所有的連接當前未被激活時，返回false。

當該函數返回false時，程序可以調用 GetLastError來接收錯誤代碼。

運行效果：

代碼：

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>
        /// 檢測網絡連接狀態
        /// </summary>
        /// <param name="urls"></param>
        public static void CheckServeStatus(string[] urls)
        {
            int errCount = 0;//ping時連接失敗個數

            if (!LocalConnectionStatus())
            {
                Console.WriteLine("網絡異常~無連接");
            }
            else if (!MyPing(urls, out errCount))
            {
                if ((double)errCount / urls.Length >= 0.3)
                {
                    Console.WriteLine("網絡異常~連接多次無響應");
                }
                else
                {
                    Console.WriteLine("網絡不穩定");
                }
            }
            else
            {
                Console.WriteLine("網絡正常");
            }
        }

        #region 網絡檢測

         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>
        /// 判斷本地的連接狀態
         /// </summary>
        /// <returns></returns>
        private static bool LocalConnectionStatus()
        {
            System.Int32 dwFlag = new Int32();
            if (!InternetGetConnectedState(ref dwFlag, 0))
            {
                Console.WriteLine("LocalConnectionStatus--未連網!");
                return false;
            }
            else
            {
                if ((dwFlag & INTERNET_CONNECTION_MODEM) != 0)
                {
                    Console.WriteLine("LocalConnectionStatus--采用調制解調器上網。");
                    return true;
                }
                else if ((dwFlag & INTERNET_CONNECTION_LAN) != 0)
                {
                    Console.WriteLine("LocalConnectionStatus--采用網卡上網。");
                    return true;
                }
            }
            return false;
        }

        /// <summary>
        /// Ping命令檢測網絡是否暢通
        /// </summary>
        /// <param name="urls">URL數據</param>
        /// <param name="errorCount">ping時連接失敗個數</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
    }
}