source: binary-improvements/7dtd-server-fixes/src/NetConnections/Servers/Telnet/TelnetConnection.cs@ 198

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

namespace AllocsFixes.NetConnections.Servers.Telnet
{
        public class TelnetConnection : IConnection
        {
                private readonly BlockingQueue<string> toClientQueue = new BlockingQueue<string> ();
                private readonly Telnet telnet;
                private readonly Thread receiveThread = null;
                private readonly Thread sendThread = null;
                private bool authenticated = false;
                private readonly bool authEnabled;
                private readonly TcpClient client;
                private readonly EndPoint endpoint;
                private readonly int endpointAddressHash;
                private bool closed = false;

                public bool IsClosed { get { return closed; } }

                public bool IsAuthenticated { get { return !authEnabled || authenticated; } }

                public int EndPointHash { get { return endpointAddressHash; } }

                public TelnetConnection (Telnet owner, TcpClient client, bool authEnabled)
                {
                        this.telnet = owner;
                        this.authEnabled = authEnabled;
                        this.client = client;
                        this.endpoint = client.Client.RemoteEndPoint;

                        if (endpoint is IPEndPoint) {
                                endpointAddressHash = ((IPEndPoint)endpoint).Address.GetHashCode ();
                        } else {
                                endpointAddressHash = endpoint.GetHashCode ();
                                Log.Out ("EndPoint is not an IPEndPoint but: " + endpoint.GetType ().ToString ());
                        }

                        Log.Out ("Telnet connection from: " + endpoint);

                        receiveThread = ThreadMaster.Create ("TelnetClientReceive_" + endpoint.ToString (), new ThreadStart (ReceiveThread));
                        receiveThread.Start ();
                        sendThread = ThreadMaster.Create ("TelnetClientSend" + endpoint.ToString (), new ThreadStart (SendThread));
                        sendThread.Start ();

                        if (authEnabled) {
                                toClientQueue.Enqueue ("Please enter password:");
                        } else {
                                LoginMessage ();
                        }
                }

                private void LoginMessage ()
                {
                        toClientQueue.Enqueue ("*** Connected with 7DTD server.");
                        toClientQueue.Enqueue ("*** Dedicated server only build");
                        toClientQueue.Enqueue ("*** Allocs server fixes loaded");
                        toClientQueue.Enqueue (string.Empty);
                        toClientQueue.Enqueue ("Server IP:   " + 
                                ((GamePrefs.GetString (EnumGamePrefs.ServerIP) != null && GamePrefs.GetString (EnumGamePrefs.ServerIP).Length != 0) ? GamePrefs.GetString (EnumGamePrefs.ServerIP) : "Any")
                        );
                        toClientQueue.Enqueue ("Server port: " + GamePrefs.GetInt (EnumGamePrefs.ServerPort));
                        toClientQueue.Enqueue ("Max players: " + GamePrefs.GetInt (EnumGamePrefs.ServerMaxPlayerCount));
                        toClientQueue.Enqueue ("Game mode:   " + GamePrefs.GetString (EnumGamePrefs.GameMode));
                        toClientQueue.Enqueue ("World:       " + GamePrefs.GetString (EnumGamePrefs.GameWorld));
                        toClientQueue.Enqueue ("Game name:   " + GamePrefs.GetString (EnumGamePrefs.GameName));
                        toClientQueue.Enqueue ("Difficulty:  " + GamePrefs.GetInt (EnumGamePrefs.GameDifficulty));
                        toClientQueue.Enqueue (string.Empty);
                        toClientQueue.Enqueue ("Press 'help' to get a list of all commands. Press 'exit' to end session.");
                        toClientQueue.Enqueue (string.Empty);
                }

                private void ReceiveThread ()
                {
                        try {
                                StreamReader reader = new StreamReader (client.GetStream ());
                                while (!closed) {
                                        string line = reader.ReadLine ();
                                        if (line != null && (line = line.Trim ()).Length > 0) {
                                                if (!IsAuthenticated) {
                                                        if (line.Equals (GamePrefs.GetString (EnumGamePrefs.TelnetPassword))) {
                                                                authenticated = true;
                                                                toClientQueue.Enqueue ("Logon successful.");
                                                                toClientQueue.Enqueue (string.Empty);
                                                                toClientQueue.Enqueue (string.Empty);
                                                                toClientQueue.Enqueue (string.Empty);
                                                                LoginMessage ();
                                                        } else {
                                                                if (telnet.RegisterFailedLogin (this)) {
                                                                        toClientQueue.Enqueue ("Password incorrect, please enter password:");
                                                                } else {
                                                                        toClientQueue.Enqueue ("Too many failed login attempts!");
                                                                        Thread.Sleep (100);
                                                                        Close (true);
                                                                        break;
                                                                }
                                                        }
                                                } else {
                                                        if (line.ToLower ().Equals ("exit")) {
                                                                break;
                                                        }
                                                        Log.Out ("Telnet executed \"" + line + "\" from: " + endpoint);
                                                        ConsoleOutputSeparator.QueueNetCommand (line, this);
                                                }
                                        }
                                }
                        } catch (Exception) {
                        }

                        if (!closed)
                                Close ();
                        ThreadMaster.Remove (Thread.CurrentThread.Name);
                }

                private void SendThread ()
                {
                        try {
                                while (!closed && client.GetStream ().CanWrite) {
                                        string line = toClientQueue.Dequeue ();
                                        if (!closed && client.GetStream ().CanWrite) {
                                                if (line == null) {
                                                        client.GetStream ().WriteByte (0);
                                                } else {
                                                        byte[] utfData = Encoding.UTF8.GetBytes (line);
                                                        client.GetStream ().Write (utfData, 0, utfData.Length);
                                                        client.GetStream ().WriteByte (13);
                                                        client.GetStream ().WriteByte (10);
                                                }
                                        }
                                }
                        } catch (Exception) {
                        }

                        if (!closed)
                                Close ();
                        ThreadMaster.Remove (Thread.CurrentThread.Name);
                }

                public void Close (bool kickedForLogins = false)
                {
                        if (!closed) {
                                closed = true;
                                toClientQueue.Close ();
                                client.GetStream ().Close ();
                                client.Close ();
                                telnet.ConnectionClosed (this);

                                if (kickedForLogins)
                                        Log.Out ("Telnet connection closed for too many login attempts: " + endpoint);
                                else
                                        Log.Out ("Telnet connection closed: " + endpoint);
                        }
                }

                public void SendLine (string line)
                {
                        if (!closed && IsAuthenticated)
                                toClientQueue.Enqueue (line);
                        else
                                toClientQueue.Enqueue (null);
                }

                public void SendLog (string text, string trace, UnityEngine.LogType type)
                {
                        throw new System.NotImplementedException ();
                }

                public string GetDescription ()
                {
                        return "Telnet from " + endpoint;
                }
        }
}