一个不错的C# Telnet类库（改进了汉字显示乱码的问题）

园友e-shizhan给出了一个不错的C# Telnet类库，但存在汉字显示乱码的问题，本人做了改进，希望对大家有用。

原文：http://www.cnblogs.com/eshizhan/archive/2010/06/03/1750661.html?login=1

原文代码：http://files.cnblogs.com/eshizhan/telnet.zip

改进后代码（注意标蓝色的部分）：

using System;
using System.Collections.Generic;
using System.Text;
using System.Net;
using System.Net.Sockets;
using System.Collections;
using System.Threading;

namespace Lwolf
{
    public class Telnet
    {
        #region telnet的数据定义
        /// <summary>       
        /// 标志符,代表是一个TELNET 指令       
        /// </summary>       
        readonly Char IAC = Convert.ToChar(255);
        /// <summary>       
        /// 表示一方要求另一方使用，或者确认你希望另一方使用指定的选项。
        /// </summary>       
        readonly Char DO = Convert.ToChar(253);
        /// <summary>
        /// 表示一方要求另一方停止使用，或者确认你不再希望另一方使用指定的选项。      
        /// </summary>      
        readonly Char DONT = Convert.ToChar(254);
        /// <summary>
        /// 表示希望开始使用或者确认所使用的是指定的选项。
        /// </summary>
        readonly Char WILL = Convert.ToChar(251);
        /// <summary>
        /// 表示拒绝使用或者继续使用指定的选项。
        /// </summary>
        readonly Char WONT = Convert.ToChar(252);
        /// <summary>
        /// 表示后面所跟的是对需要的选项的子谈判
        /// </summary>
        readonly Char SB = Convert.ToChar(250);
        /// <summary>
        /// 子谈判参数的结束
        /// </summary>
        readonly Char SE = Convert.ToChar(240);
        const Char IS = '0';
        const Char SEND = '1';
        const Char INFO = '2';
        const Char VAR = '0';
        const Char VALUE = '1';
        const Char ESC = '2';
        const Char USERVAR = '3';
        /// <summary>
        /// 流
        /// /// </summary>
        byte[] m_byBuff = new byte[100000];
        /// <summary>
        /// 收到的控制信息
        /// </summary>
        private ArrayList m_ListOptions = new ArrayList();
        /// <summary>
        /// 存储准备发送的信息
        /// </summary>
        string m_strResp;
        /// <summary>
        /// 一个Socket套接字
        /// </summary>
        private Socket s;
        #endregion

        private IPEndPoint iep;
        private string address;
        private int port;
        private int timeout;

        private string strWorkingData = "";     // 保存从服务器端接收到的数据
        private string strFullLog = "";
        //==== 夏春涛 扩充 20110531 ================================================           

        private string strWorkingDataX = "";
        //用于获取当前工作的数据内容

        public string WorkingData
        {
            get { return strWorkingDataX; }
        }
        //===================================================================
        public Telnet(string Address, int Port, int CommandTimeout)
        {
            address = Address;
            port = Port;
            timeout = CommandTimeout;
        }

        /// <summary>       
        /// 启动socket 进行telnet操作       
        /// </summary>      
        public bool Connect()
        {

            IPAddress import = GetIP(address);

            s = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

            iep = new IPEndPoint(import, port);

            try
            {
                // Try a blocking connection to the server
                s = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

                s.Connect(iep);

          //异步回调
                AsyncCallback recieveData = new AsyncCallback(OnRecievedData);
                s.BeginReceive(m_byBuff, 0, m_byBuff.Length, SocketFlags.None, recieveData, s);

                return true;
            }
            catch (Exception)
            {
                return false;
            }
        }

        /// <summary>       
        /// 当接收完成后,执行的方法(供委托使用)      
        /// </summary>     
        /// <param name="ar"></param>      
        private void OnRecievedData(IAsyncResult ar)
        {
            try
            {
                //从参数中获得给的socket 对象          
                Socket sock = (Socket)ar.AsyncState;

                //EndReceive方法为结束挂起的异步读取        
                int nBytesRec = sock.EndReceive(ar);
                //如果有接收到数据的话           
                if (nBytesRec > 0)
                {
                    //声明一个字符串,用来存储解析过的字符串               
                    string m_strLine = "";
                    //遍历Socket接收到的字符                
                    /*      
                     * 此循环用来调整linux 和 windows在换行上标记的区别      
                     * 最后将调整好的字符赋予给 m_strLine     
                     */
                    for (int i = 0; i < nBytesRec; i++)
                    {
                        Char ch = Convert.ToChar(m_byBuff[i]);
                        switch (ch)
                        {
                            case '\r':
                                m_strLine += Convert.ToString("\r\n");
                                break;
                            case '\n':
                                break;
                            default:
                                m_strLine += Convert.ToString(ch);
                                break;
                        }
                    }
                    try
                    {
                        //获得转义后的字符串的长度                 
                        int strLinelen = m_strLine.Length;
                        //如果长度为零                  
                        if (strLinelen == 0)
                        {
                            //则返回"\r\n" 即回车换行                   
                            m_strLine = Convert.ToString("\r\n");
                        }
                        //建立一个流,把接收的信息(转换后的)存进 mToProcess 中  
                        Byte[] mToProcess = new Byte[strLinelen];
                        for (int i = 0; i < strLinelen; i++)
                            mToProcess[i] = Convert.ToByte(m_strLine[i]);
                        //对接收的信息进行处理,包括对传输过来的信息的参数的存取和      
                        string mOutText = ProcessOptions(mToProcess);
                        //==== 夏春涛 扩充 20110531 ==============================================
                        mOutText = ConvertToGB2312(mOutText);
                        strWorkingDataX = mOutText;
                        //===================================================================
                        //解析命令后返回 显示信息(即除掉了控制信息)                       
                        if (mOutText != "")
                        {
                            //Console.Write(mOutText);//显示输出//夏春涛 去掉 20110531/////////////////////////
                            strWorkingData = mOutText;
                            strFullLog += mOutText;
                        }
                        //接收完数据,处理完字符串数据等一系列事物之后,开始回发数据         
                        RespondToOptions();
                    }
                    catch (Exception ex)
                    {
                        throw new Exception("接收数据的时候出错了! " + ex.Message);
                    }
                }
                else// 如果没有接收到任何数据的话          
                {
                    // 关闭连接           
                    // 关闭socket              
                    sock.Shutdown(SocketShutdown.Both);
                    sock.Close();
                }
            }
            catch { }
        }
        /// <summary>       
        ///  发送数据的函数      
        /// </summary>       
        private void RespondToOptions()
        {
            try
            {
                //声明一个字符串,来存储 接收到的参数           
                string strOption;
                /*              
                 * 此处的控制信息参数,是之前接受到信息之后保存的             
                 * 例如 255   253   23   等等                               
                 */
                for (int i = 0; i < m_ListOptions.Count; i++)
                {
                    //获得一个控制信息参数                  
                    strOption = (string)m_ListOptions[i];
                    //根据这个参数,进行处理                  
                    ArrangeReply(strOption);
                }
                DispatchMessage(m_strResp);
                m_strResp = "";
                m_ListOptions.Clear();
            }
            catch (Exception ers)
            {
                Console.WriteLine("出错了,在回发数据的时候 " + ers.Message);

            }
        }
        /// <summary>       
        /// 解析接收的数据,生成最终用户看到的有效文字,同时将附带的参数存储起来      
        ///</summary>      
        ///<param name="m_strLineToProcess">收到的处理后的数据</param>    
        /// <returns></returns>    
        private string ProcessOptions(byte[] m_strLineToProcess)
        {
            string m_DISPLAYTEXT = "";
            string m_strTemp = "";
            string m_strOption = "";
            string m_strNormalText = "";
            bool bScanDone = false;
            int ndx = 0;
            int ldx = 0;
            char ch;
            try
            {
                //把数据从byte[] 转化成string   
                for (int i = 0; i < m_strLineToProcess.Length; i++)
                {
                    Char ss = Convert.ToChar(m_strLineToProcess[i]);
                    m_strTemp = m_strTemp + Convert.ToString(ss);
                }
                               
                //此处意义为,当没描完数据前,执行扫描     
                while (bScanDone != true)
                {
                    //获得长度               
                    int lensmk = m_strTemp.Length;
                    //之后开始分析指令,因为每条指令为255 开头,故可以用此来区分出每条指令
                    ndx = m_strTemp.IndexOf(Convert.ToString(IAC));
                    //此处为出错判断,本无其他含义              
                    if (ndx > lensmk)
                        ndx = m_strTemp.Length;

                    //此处为,如果搜寻到IAC标记的telnet 指令,则执行以下步骤       
                    if (ndx != -1)
                    {
                        #region 如果存在IAC标志位
                        // 将 标志位IAC 的字符 赋值给最终显示文字          
                        m_DISPLAYTEXT += m_strTemp.Substring(0, ndx);
                        // 此处获得命令码             
                        ch = m_strTemp[ndx + 1];
                        //如果命令码是253(DO) 254(DONT)  521(WILL) 252(WONT) 的情况下
                        if (ch == DO || ch == DONT || ch == WILL || ch == WONT)
                        {

                            //将以IAC 开头3个字符组成的整个命令存储起来         
                            m_strOption = m_strTemp.Substring(ndx, 3);
                            m_ListOptions.Add(m_strOption);
                            // 将 标志位IAC 的字符 赋值给最终显示文字                        
                            m_DISPLAYTEXT += m_strTemp.Substring(0, ndx);
                            //将处理过的字符串删去                         
                            string txt = m_strTemp.Substring(ndx + 3);
                            m_strTemp = txt;
                        }
                        //如果IAC后面又跟了个IAC (255) 
                        else if (ch == IAC)
                        {
                            //则显示从输入的字符串头开始,到之前的IAC 结束       
                            m_DISPLAYTEXT = m_strTemp.Substring(0, ndx);
                            //之后将处理过的字符串排除出去                 
                            m_strTemp = m_strTemp.Substring(ndx + 1);
                        }
                        //如果IAC后面跟的是SB(250)      
                        else if (ch == SB)
                        {
                            m_DISPLAYTEXT = m_strTemp.Substring(0, ndx);
                            ldx = m_strTemp.IndexOf(Convert.ToString(SE));
                            m_strOption = m_strTemp.Substring(ndx, ldx);
                            m_ListOptions.Add(m_strOption);
                            m_strTemp = m_strTemp.Substring(ldx);
                        }
                        #endregion
                    }
                    //若字符串里已经没有IAC标志位了 
                    else
                    {

                        //显示信息累加上m_strTemp存储的字段     
                        m_DISPLAYTEXT = m_DISPLAYTEXT + m_strTemp;
                        bScanDone = true;
                    }
                }
                //输出人看到的信息   
                m_strNormalText = m_DISPLAYTEXT;
            }
            catch (Exception eP)
            {
                throw new Exception("解析传入的字符串错误:" + eP.Message);
            }
           
            return m_strNormalText;
        }
        /// <summary>     
        /// 获得IP地址     
        /// </summary>      
        /// <param name="import"></param>   
        /// <returns></returns>  
        private static IPAddress GetIP(string import)
        {
            IPHostEntry IPHost = Dns.GetHostEntry(import);
            return IPHost.AddressList[0];
        }

        #region magic Function
        //解析传过来的参数,生成回发的数据到m_strResp  
        private void ArrangeReply(string strOption)
        {
            try
            {
                Char Verb;
                Char Option;
                Char Modifier;
                Char ch;
                bool bDefined = false;
                //排错选项,无啥意义             
                if (strOption.Length < 3) return;
                //获得命令码              
                Verb = strOption[1];
                //获得选项码            
                Option = strOption[2];
                //如果选项码为 回显(1) 或者是抑制继续进行(3)
                if (Option == 1 || Option == 3)
                {
                    bDefined = true;
                }
                // 设置回发消息,首先为标志位255        
                m_strResp += IAC;
                //如果选项码为 回显(1) 或者是抑制继续进行(3) ==true  
                if (bDefined == true)
                {
                    #region 继续判断
                    //如果命令码为253 (DO)            
                    if (Verb == DO)
                    {
                        //我设置我应答的命令码为 251(WILL) 即为支持 回显或抑制继续进行    
                        ch = WILL;
                        m_strResp += ch;
                        m_strResp += Option;
                    }
                    //如果命令码为 254(DONT)    
                    if (Verb == DONT)
                    {
                        //我设置我应答的命令码为 252(WONT) 即为我也会"拒绝启动" 回显或抑制继续进行
                        ch = WONT;
                        m_strResp += ch;
                        m_strResp += Option;
                    }
                    //如果命令码为251(WILL)  
                    if (Verb == WILL)
                    {
                        //我设置我应答的命令码为 253(DO) 即为我认可你使用回显或抑制继续进行
                        ch = DO;
                        m_strResp += ch;
                        m_strResp += Option;
                        //break;              
                    }
                    //如果接受到的命令码为251(WONT)        
                    if (Verb == WONT)
                    {
                        //应答  我也拒绝选项请求回显或抑制继续进行      
                        ch = DONT;
                        m_strResp += ch;
                        m_strResp += Option;
                        //break;           
                    }
                    //如果接受到250(sb,标志子选项开始)           
                    if (Verb == SB)
                    {
                        /*                 
                         * 因为启动了子标志位,命令长度扩展到了4字节,                   
                         * 取最后一个标志字节为选项码                    
                         * 如果这个选项码字节为1(send)                   
                         * 则回发为 250(SB子选项开始) + 获取的第二个字节 + 0(is) + 255(标志位IAC) + 240(SE子选项结束)              
                         */
                        Modifier = strOption[3];
                        if (Modifier == SEND)
                        {
                            ch = SB;
                            m_strResp += ch;
                            m_strResp += Option;
                            m_strResp += IS;
                            m_strResp += IAC;
                            m_strResp += SE;
                        }
                    }
                    #endregion
                }
                else //如果选项码不是1 或者3
                {
                    #region 底下一系列代表,无论你发那种请求,我都不干
                    if (Verb == DO)
                    {
                        ch = WONT;
                        m_strResp += ch;
                        m_strResp += Option;
                    }
                    if (Verb == DONT)
                    {
                        ch = WONT;
                        m_strResp += ch;
                        m_strResp += Option;
                    }
                    if (Verb == WILL)
                    {
                        ch = DONT;
                        m_strResp += ch;
                        m_strResp += Option;
                    }
                    if (Verb == WONT)
                    {
                        ch = DONT;
                        m_strResp += ch;
                        m_strResp += Option;
                    }
                    #endregion
                }
            }
            catch (Exception eeeee)
            {
                throw new Exception("解析参数时出错:" + eeeee.Message);
            }
        }
        /// <summary>    
        /// 将信息转化成charp[] 流的形式,使用socket 进行发出  
        /// 发出结束之后,使用一个匿名委托,进行接收, 
        /// 之后这个委托里,又有个委托,意思是接受完了之后执行OnRecieveData 方法
        ///      
        /// </summary>      
        /// <param name="strText"></param> 
        void DispatchMessage(string strText)
        {
            try
            {
                //申请一个与字符串相当长度的char流     
                Byte[] smk = new Byte[strText.Length];
                for (int i = 0; i < strText.Length; i++)
                {
                    //解析字符串,将其存储到char流中去  
                    Byte ss = Convert.ToByte(strText[i]);
                    smk[i] = ss;
                }
                //发送char流,之后发送完毕后执行委托中的方法(此处为匿名委托)   
                IAsyncResult ar2 = s.BeginSend(smk, 0, smk.Length, SocketFlags.None, delegate(IAsyncResult ar)
                {
                    //当执行完"发送数据" 这个动作后                 
                    // 获取Socket对象,对象从beginsend 中的最后个参数上获得         
                    Socket sock1 = (Socket)ar.AsyncState;
                    if (sock1.Connected)//如果连接还是有效                   
                    {
                        //这里建立一个委托     
                        AsyncCallback recieveData = new AsyncCallback(OnRecievedData);

                        sock1.BeginReceive(m_byBuff, 0, m_byBuff.Length, SocketFlags.None, recieveData, sock1);
                     
                    }
                }, s);

                s.EndSend(ar2);
            }
            catch (Exception ers)
            {
                Console.WriteLine("出错了,在回发数据的时候:" + ers.Message);
            }
        }

        /// <summary>
        /// 等待指定的字符串返回
        /// </summary>
        /// <param name="DataToWaitFor">等待的字符串</param>
        /// <returns>返回0</returns>
        public int WaitFor(string DataToWaitFor)
        {
            long lngStart = DateTime.Now.AddSeconds(this.timeout).Ticks;
            long lngCurTime = 0;

            while (strWorkingData.ToLower().IndexOf(DataToWaitFor.ToLower()) == -1)
            {
                lngCurTime = DateTime.Now.Ticks;
                if (lngCurTime > lngStart)
                {
                    throw new Exception("Timed Out waiting for : " + DataToWaitFor);
                }
                Thread.Sleep(1);
            }
            strWorkingData = "";
            return 0;
        }

        public void Send(string message)
        {
            DispatchMessage(message);
            //因为每发送一行都没有发送回车,故在此处补上        
            DispatchMessage("\r\n");
        }
        #endregion

        /// <summary>
        /// 取完整日志
        /// </summary>
        public string SessionLog
        {
            get
            {
                return strFullLog;
            }
        }

        //======================================================================================
        /// <summary>
        /// 字符串编码转换，解决汉字显示乱码问题。

        /// 原始字符串中的汉字存储的是汉字内码，此代码实质是将汉字内码转换为GB2312编码。（夏春涛20110531）
        /// </summary>
        /// <param name="str_origin">需要转换的字符串</param>
        /// <returns>转换后的字符串</returns>
        private string ConvertToGB2312(string str_origin)
        {
            char[] chars = str_origin.ToCharArray();
            byte[] bytes = new byte[chars.Length];
            for (int i = 0; i < chars.Length; i++)
            {
                int c = (int)chars[i];
                bytes[i] = (byte)c;
            }
            Encoding Encoding_GB2312 = Encoding.GetEncoding("GB2312");
            string str_converted = Encoding_GB2312.GetString(bytes);
            return str_converted;
        }
        //======================================================================================
    }
}