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[ASP.net教程]C#访问远程主机资源的方法


实现访问远程主机的共享目录中的一个文件的解决方法:

一、调用Net use命令

        // 使用方法:
        //if (Connect("192.168.1.48", "用户名", "密码"))   
        //{
        //    File.Copy(@"\\192.168.1.48\共享目录\test.txt",   @"e:\\test.txt",   true);   
        //}
        public bool Connect(string remoteHost, string userName, string passWord)
        {
            bool Flag = true;
            Process proc = new Process();
            proc.StartInfo.FileName = "cmd.exe";
            proc.StartInfo.UseShellExecute = false;
            proc.StartInfo.RedirectStandardInput = true;
            proc.StartInfo.RedirectStandardOutput = true;
            proc.StartInfo.RedirectStandardError = true;
            proc.StartInfo.CreateNoWindow = true;
            try
            {
                proc.Start();
                string command = @"net  use  \\" + remoteHost + "  " + passWord + "  " + "  /user:" + userName + ">NUL";
                proc.StandardInput.WriteLine(command);
                command = "exit";
                proc.StandardInput.WriteLine(command);
                while (proc.HasExited == false)
                {
                    proc.WaitForExit(1000);
                }
                string errormsg = proc.StandardError.ReadToEnd();
                if (errormsg != "")
                    Flag = false;
                proc.StandardError.Close();
            }
            catch (Exception ex)
            {
                Flag = false;
            }
            finally
            {
                proc.Close();
                proc.Dispose();
            }
            return Flag;
        }



二、调用WNetAddConnection2、WNetAddConnection3或者NetUseAdd函数,进行磁盘映射。

using System;
using System.Collections.Generic;
using System.Text;       
using System.Runtime.InteropServices;

namespace WindowsApplication1
{
    public class MyMap
    {
        [DllImport("mpr.dll", EntryPoint = "WNetAddConnection2")]
        public static extern uint WNetAddConnection2(
            [In] NETRESOURCE lpNetResource,
            string lpPassword,
            string lpUsername,
            uint dwFlags);
        
        [DllImport("Mpr.dll")]
        public static extern uint WNetCancelConnection2(
            string lpName,
            uint dwFlags,
            bool fForce);
        
        [StructLayout(LayoutKind.Sequential)]
        public class NETRESOURCE
        {
            public int dwScope;
            public int dwType;
            public int dwDisplayType;
            public int dwUsage;
            public string LocalName;
            public string RemoteName;
            public string Comment;
            public string Provider;
        }

        // remoteNetworkPath format:  @"\\192.168.1.48\sharefolder"
        // localDriveName format:     @"E:"
        public static bool CreateMap(string userName, string password, string remoteNetworkPath, string localDriveName)
        {            
            NETRESOURCE myNetResource = new NETRESOURCE();
            myNetResource.dwScope = 2;       //2:RESOURCE_GLOBALNET
            myNetResource.dwType = 1;        //1:RESOURCETYPE_ANY
            myNetResource.dwDisplayType = 3; //3:RESOURCEDISPLAYTYPE_GENERIC
            myNetResource.dwUsage = 1;       //1: RESOURCEUSAGE_CONNECTABLE
            myNetResource.LocalName = localDriveName;
            myNetResource.RemoteName = remoteNetworkPath;
            myNetResource.Provider = null;

            uint nret = WNetAddConnection2(myNetResource, password, userName, 0);

            if (nret == 0)
                return true;
            else
                return false;
        }

        // localDriveName format:     @"E:"
        public static bool DeleteMap(string localDriveName)
        {
            uint nret = WNetCancelConnection2(localDriveName, 1, true);

            if (nret == 0)
                return true;
            else
                return false;
        }

        public void test()
        {
            // 注意:
            // remote、local、username的格式一定要正确,否则可能出现错误
            string remote = @"\\192.168.1.48\generals";
            string local = @"P:";
            string username = @"Domain\UserName";
            string password = @"Password";
            bool ret = MyMap.CreateMap(username, password, remote, local);
            if (ret)
            {
                //do what you want:
                // ...
                //File.Copy("q:\\test.htm", "c:\\test.htm");

                MyMap.DeleteMap(local);
            }
        }
    }
}

三、使用WebClient类

由于WebClient类可以上传下载文件,并且支持以http:、https:和file:开头的URI,所以可以用WebClient类来传输文件。
添加System.Net命名空间后使用如下代码下载文件:

        private void Test1()
        {
            try
            {
                WebClient client = new WebClient();
                NetworkCredential cred = new NetworkCredential("username", "password", "172.16.0.222");
                client.Credentials = cred;
                client.DownloadFile("file://172.16.0.222/test/111.txt", "111.txt");
            }
            catch (Exception ex)
            {
                // 如果网络很慢,而文件又很大,这时可能有超时异常(Time out)。
            }
        }

        public void Test2()
        {
            try
            {
                WebClient client = new WebClient();
                NetworkCredential cred = new NetworkCredential("username", "password", "domain");
                client.Credentials = cred;
                client.DownloadFile("file://172.16.0.222/test/111.txt", "111.txt");
            }
            catch (Exception ex)
            {
                // 如果网络很慢,而文件又很大,这时可能有超时异常(Time out)。
            }
        }


类似的还可以试试WebRequest、FileWebRequest等:

                WebRequest req = WebRequest.Create("file://138.12.12.14/generals/test.htm");
                NetworkCredential cred = new NetworkCredential("username", "password", "IP");
                req.Credentials = cred;
                WebResponse response = req.GetResponse();
                Stream strm = response.GetResponseStream();
                StreamReader r = new StreamReader(strm);
                ... ...



四、角色模拟

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
using System.Security.Principal;
using System.IO;

namespace Test
{
    public class Test
    {
        // logon types
        const int LOGON32_LOGON_INTERACTIVE = 2;
        const int LOGON32_LOGON_NETWORK = 3;
        const int LOGON32_LOGON_NEW_CREDENTIALS = 9;
        // logon providers
        const int LOGON32_PROVIDER_DEFAULT = 0;
        const int LOGON32_PROVIDER_WINNT50 = 3;
        const int LOGON32_PROVIDER_WINNT40 = 2;
        const int LOGON32_PROVIDER_WINNT35 = 1;

        [DllImport("advapi32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        public static extern int LogonUser(String lpszUserName,
            String lpszDomain,
            String lpszPassword,
            int dwLogonType,
            int dwLogonProvider,
            ref IntPtr phToken);

        [DllImport("advapi32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        public static extern int DuplicateToken(IntPtr hToken,
            int impersonationLevel,
            ref IntPtr hNewToken);

        [DllImport("advapi32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        public static extern bool RevertToSelf();

        [DllImport("kernel32.dll", CharSet = CharSet.Auto)]
        public static extern bool CloseHandle(IntPtr handle);

        private WindowsImpersonationContext impersonationContext;

        public bool impersonateValidUser(String userName, String domain, String password)
        {
            WindowsIdentity tempWindowsIdentity;
            IntPtr token = IntPtr.Zero;
            IntPtr tokenDuplicate = IntPtr.Zero;

            if (RevertToSelf())
            {
                // 这里使用LOGON32_LOGON_NEW_CREDENTIALS来访问远程资源。
                // 如果要(通过模拟用户获得权限)实现服务器程序,访问本地授权数据库可
                // 以用LOGON32_LOGON_INTERACTIVE
                if (LogonUser(userName, domain, password, LOGON32_LOGON_NEW_CREDENTIALS,
                    LOGON32_PROVIDER_DEFAULT, ref token) != 0)
                {
                    if (DuplicateToken(token, 2, ref tokenDuplicate) != 0)
                    {
                        tempWindowsIdentity = new WindowsIdentity(tokenDuplicate);
                        impersonationContext = tempWindowsIdentity.Impersonate();
                        if (impersonationContext != null)
                        {
                            System.AppDomain.CurrentDomain.SetPrincipalPolicy(PrincipalPolicy.WindowsPrincipal);
                            IPrincipal pr = System.Threading.Thread.CurrentPrincipal;
                            IIdentity id = pr.Identity;
                            CloseHandle(token);
                            CloseHandle(tokenDuplicate);
                            return true;
                        }
                    }
                }
            }

            if (token != IntPtr.Zero)
                CloseHandle(token);

            if (tokenDuplicate != IntPtr.Zero)
                CloseHandle(tokenDuplicate);

            return false;
        }

        public void undoImpersonation()
        {
            impersonationContext.Undo();
        }

        public void TestFunc()
        {
            bool isImpersonated = false;
            try
            {
                if (impersonateValidUser("UserName", "Domain", "Password"))
                {
                    isImpersonated = true;
                    //do what you want now, as the special user
                    // ...
                    File.Copy(@"\\192.168.1.48\generals\now.htm", "c:\\now.htm", true);
                }
            }
            finally
            {
                if (isImpersonated)
                    undoImpersonation();
            }
        }
    }
}


五、比较

方法一通过调用Shell命令Net Use实现,有点笨拙。
方法二和方法一有些相似之处。映射远程资源,然后访问。
方法三由于会有超时异常出现,所以在网络速度快、传输小文件时是可以的。
方法四通过身份模拟实现远程资源访问。一些服务器进程就是通过这种方式运行的。这种方法也是我的最爱。

六、要注意的地方

关于这几种方法,google后都可以找到一些文章。但是等到自己实际测试时,有时会出现各种小错误,
这些错误基本来源于两方面:

1、函数的参数选择有问题,和自己的环境不相符。
比如        
public static extern int LogonUser(String lpszUserName,
            String lpszDomain,
            String lpszPassword,
            int dwLogonType,
            int dwLogonProvider,
            ref IntPtr phToken);
中的dwLogonType,要访问远程资源就要用LOGON32_LOGON_NEW_CREDENTIALS,
要模拟本机用户就要用LOGON32_LOGON_INTERACTIVE。

2、函数的参数格式有问题。

    a、比如
    public static extern int LogonUser(String lpszUserName,
            String lpszDomain,
            String lpszPassword,
            int dwLogonType,
            int dwLogonProvider,
            ref IntPtr phToken);
    中的lpszUserName、lpszDomain、lpszPassword就要写清楚。

    我就在这遇到过问题,第一次测试时,远程服务器就是一台独立的文件服务器,这是我的调用方式:
        LogonUser("myname", "192.168.1.48", "password", LOGON32_LOGON_NEW_CREDENTIALS,
                    LOGON32_PROVIDER_DEFAULT, ref token);

    第二次测试时,远程服务器是域MyDomain中的一个成员服务器,提供文件服务。这时代码就应该是:
        LogonUser("myname", "MyDomain", "password", LOGON32_LOGON_NEW_CREDENTIALS,
                    LOGON32_PROVIDER_DEFAULT, ref token);

    注意,代码中是MyDomain而不是IP地址。


    b、再如:

    参考上面代码
            string remote = @"\\192.168.1.48\generals";
            string local = @"P:";
            string username = @"Domain\UserName";
            string password = @"Password";

    如果@"\\192.168.1.48\generals"变成@"\\192.168.1.48\generals\”就会出错;
    如果是域中的用户,那么把@"Domain\UserName"变成@"UserName"就会出错。