C# 实现Telnet | 易学教程

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

namespace BLL
{
    public class TelnetClient
    {
        private TcpClient Client;
        private NetworkStream ns;
        private string m_LogonPrompt = "ogin:";
        private string m_PasswordPrompt = "assword:";
        private readonly int BuffSize = 1024 * 4;

        /// <summary>
        /// 登录输入用户名提示字符
        /// 默认值：ogin:
        /// </summary>
        public string LoginPrompt
        {
            set { m_LogonPrompt = value; }
            get { return m_LogonPrompt; }
        }
        /// <summary>
        /// 登录输入密码提示字符
        /// 默认值：assword:
        /// </summary>
        public string PasswordPrompt
        {
            set { m_PasswordPrompt = value; }
            get { return m_PasswordPrompt; }
        }
        /// <summary>
        /// 连接状态
        /// </summary>
        public bool Connected
        {
            get { return Client != null ? Client.Connected : false; }
        }
        /// <summary>
        /// 连接远端主机
        /// </summary>
        /// <param name="hostname">主机名称</param>
        /// <param name="port">端口</param>
        /// <returns>远端主机响应文本</returns>
        public string Connect(string hostname, int port)
        {
            string result = string.Empty;
            try
            {
                Client = new TcpClient(hostname, port);
                ns = Client.GetStream();
                result = Negotiate();
            }
            catch (Exception e)
            {
                result = e.Message;
            }
            return result;
        }
        /// <summary>
        /// 连接远端主机并登录
        /// </summary>
        /// <param name="hostname">主机名称</param>
        /// <param name="port">端口</param>
        /// <param name="username">用户名</param>
        /// <param name="password">密码</param>
        /// <param name="waitTime">连接等待时间</param>
        /// <returns></returns>
        public string Connect(string hostname, int port, string username, string password, int waitTime)
        {
            string result = string.Empty;
            result = Connect(hostname, port);
            if (Connected && result.EndsWith(LoginPrompt))
            {
                Send(username, waitTime);
                result = Receive();
                if (result.EndsWith(PasswordPrompt))
                {
                    Send(password, waitTime);
                    result = Receive();
                    if (!result.EndsWith("<"))
                    {
                        Client.Close();
                        result = "Logon Error";
                    }
                }
            }
            return result;
        }
        /// <summary>
        /// 接收
        /// </summary>
        /// <returns>传回的数据</returns>
        public string Receive()
        {
            StringBuilder result = new StringBuilder();
            if (Connected && ns.CanRead)
            {
                byte[] buff = new byte[BuffSize];
                int numberOfRead = 0;
                do
                {
                    numberOfRead = ns.Read(buff, 0, BuffSize);
                    result.AppendFormat("{0}", Encoding.ASCII.GetString(buff, 0, numberOfRead));
                }
                while (ns.DataAvailable);
            }
            return result.ToString().Trim();
        }
        /// <summary>
        /// 发送
        /// </summary>
        /// <param name="cmd">指令</param>
        /// <param name="waitTime">等待超时时间（毫秒）</param>
        public void Send(string cmd, int waitTime)
        {
            if (Connected && ns.CanWrite)
            {
                cmd += "\r\n";
                byte[] buff = Encoding.ASCII.GetBytes(cmd);
                ns.Write(buff, 0, buff.Length);
                System.Threading.Thread.Sleep(waitTime);
            }
        }
         /// <summary>
        /// 关闭
        /// </summary>
        public void Close()
        {
            Client.Close();
        }
        /// <summary>
        /// 处理Telnet选项谈判，直到出现用户名输入提示
        /// </summary>
        /// <returns></returns>
        private string Negotiate()
        {
            string result = string.Empty;
            if (Connected)
            {
                while (true)
                {
                    byte[] rev = ReceiveBytes();
                    result = Encoding.ASCII.GetString(rev).Trim();
                    if (result.EndsWith(LoginPrompt))
                    {
                        break;
                    }
                    int count = rev.Length / 3;
                    for (int i = 0; i < count; i++)
                    {
                        int iac = rev[i * 3];
                        int cmd = rev[i * 3 + 1];
                        int value = rev[i * 3 + 2];
                        if (((int)Verbs.IAC) != iac)
                        {
                            continue;
                        }
                        switch (cmd)
                        {
                            case (int)Verbs.DO:
                                ns.WriteByte((byte)iac);
                                ns.WriteByte(value == (int)Options.RD ? (byte)Verbs.WILL : (byte)Verbs.WONT);
                                ns.WriteByte((byte)value);
                                break;
                            case (int)Verbs.DONT:
                                ns.WriteByte((byte)iac);
                                ns.WriteByte((byte)Verbs.WONT);
                                ns.WriteByte((byte)value);
                                break;
                            case (int)Verbs.WILL:
                                ns.WriteByte((byte)iac);
                                ns.WriteByte(value == (int)Options.SGA ? (byte)Verbs.DO : (byte)Verbs.DONT);
                                ns.WriteByte((byte)value);
                                break;
                            case (int)Verbs.WONT:
                                ns.WriteByte((byte)iac);
                                ns.WriteByte((byte)Verbs.DONT);
                                ns.WriteByte((byte)value);
                                break;
                            default:
                                break;
                        }
                    }
                }
            }
            return result;
        }
        /// <summary>
        /// 读取字节流
        /// </summary>
        /// <returns></returns>
        private byte[] ReceiveBytes()
        {
            byte[] result = new byte[0];
            byte[] buff = new byte[BuffSize];
            int numberOfRead = 0;
            if (Connected && ns.CanRead)
            {
                numberOfRead = ns.Read(buff, 0, BuffSize);
                result = new byte[numberOfRead];
                Array.Copy(buff, result, numberOfRead);
            }            return result;
        }
    }
    enum Verbs
    {
        WILL = 251,
        WONT = 252,
        DO = 253,
        DONT = 254,
        IAC = 255
    }
    enum Options
    {
        RD = 1,
        SGA = 3
    }
}

来源：https://www.cnblogs.com/yinchengliang/archive/2012/06/05/2536887.html

标签

string

telnet