source: binary-improvements/7dtd-server-fixes/src/AllocsNetTelnetServer.cs@ 74

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

public class AllocsNetTelnetServer
{
        private class Connection
        {
                private bool authenticated = false;
                private TcpClient client;
                private NetworkStream stream;
                private string lineBuffer = string.Empty;
                private EndPoint endpoint;

                public Connection (TcpClient client)
                {
                        this.client = client;
                        this.stream = client.GetStream ();
                        this.endpoint = client.Client.RemoteEndPoint;
                }

                public EndPoint GetEndPoint ()
                {
                        return endpoint;
                }

                private void WriteByte (byte v)
                {
                        if (!IsClosed () && stream.CanWrite) {
                                stream.WriteByte (v);
                        }
                }

                public void WriteLine (string s)
                {
                        if (!IsClosed () && stream.CanWrite) {
                                for (int i = 0; i < s.Length; i++) {
                                        WriteByte ((byte)s [i]);
                                }
                                WriteByte (10);
                        }
                }

                public void Close ()
                {
                        if (client != null)
                                client.Close ();
                        client = null;
                }

                public bool IsClosed ()
                {
                        if (client != null && !client.Connected) {
                                Log.Out ("Telnet connection interrupted: " + endpoint);
                        }
                        return (client == null) || (!client.Connected);
                }

                public bool IsAuthenticated ()
                {
                        return !authEnabled || authenticated;
                }

                public void SetAuthenticated ()
                {
                        authenticated = true;
                }

                public bool Read ()
                {
                        while (!IsClosed() && stream.CanRead && stream.DataAvailable) {
                                int b = stream.ReadByte ();
                                if (b == '\r' || b == '\n') {
                                        if (lineBuffer.Length > 0)
                                                return true;
                                } else {
                                        lineBuffer += (char)b;
                                }
                        }
                        return false;
                }

                public string GetLine ()
                {
                        string res = lineBuffer;
                        lineBuffer = string.Empty;
                        return res;
                }
        }

        private static cl004c console = null;
        private static Thread telnetThread = null;
        private static TcpListener listener = null;
        private static bool closed = false;
        private static bool authEnabled = false;
        private static List<Connection> conns = new List<Connection> ();

        public static void init (int port)
        {
                Log.Out ("[7dtd-server-fixes by Alloc] Version: " + Assembly.GetExecutingAssembly().GetName().Version);
                authEnabled = GamePrefs.GetString (EnumGamePrefs.TelnetPassword).Length != 0;
                if (authEnabled)
                        listener = new TcpListener (IPAddress.Any, port);
                else
                        listener = new TcpListener (IPAddress.Loopback, port);
                telnetThread = ThreadMaster.Create ("thread Allocs TelnetListenThread", new ThreadStart (telnetListenThread));
                telnetThread.Start ();
                Log.Out ("Started Allocs NetTelnetServer thread on " + port);
        }

        private static void telnetListenThread ()
        {
                try {
                        Log.Out ("Started thread_Allocs_TelnetListenThread()");
                        listener.Start ();
                        while (!closed) {
                                Thread.Sleep (10);
                                if (listener.Pending ()) {
                                        Connection c = new Connection (listener.AcceptTcpClient ());
                                        conns.Add (c);
                                        Log.Out ("Telnet connection from: " + c.GetEndPoint ());
                                        if (authEnabled) {
                                                c.WriteLine ("Please enter password:");
                                        } else {
                                                LoginMessage (c);
                                        }
                                }

                                foreach (Connection c in conns) {
                                        if (c.IsClosed ()) {
                                                c.Close ();
                                                conns.Remove (c);
                                                break;
                                        }
                                        if (c.Read ()) {
                                                string line = lineCorrecter (c.GetLine ());
                                                if (!c.IsAuthenticated ()) {
                                                        if (line.Equals (GamePrefs.GetString (EnumGamePrefs.TelnetPassword))) {
                                                                c.SetAuthenticated ();
                                                                c.WriteLine ("Logon successful.");
                                                                c.WriteLine (string.Empty);
                                                                c.WriteLine (string.Empty);
                                                                c.WriteLine (string.Empty);
                                                                LoginMessage (c);
                                                        } else {
                                                                c.WriteLine ("Password incorrect, please enter password:");
                                                        }
                                                } else {
                                                        if (line.ToLower ().Equals ("exit")) {
                                                                Log.Out ("Telnet connection closed by client: " + c.GetEndPoint ());
                                                                c.Close ();
                                                                conns.Remove (c);
                                                                break;
                                                        }

                                                        Log.Out ("Telnet executed \"" + line + "\" from: " + c.GetEndPoint ());
                                                        console.md000f (line);
                                                }
                                        }
                                }
                        }
                        Log.Out ("Exited thread_Allocs_TelnetListenThread()");
                        ThreadMaster.Remove (Thread.CurrentThread.Name);
                } catch (Exception ex) {
                        Log.Out ("Error in Allocs telnetListenThread: " + ex.Message);
                        Log.Out ("Stack Trace: " + ex.StackTrace);
                }
        }

        private static void LoginMessage (Connection c)
        {
                c.WriteLine ("*** Connected with 7DTD server.");
                c.WriteLine ("*** Server version: Alpha 8.7 (b29) Compatibility Version: Alpha 8.7");
                c.WriteLine (string.Empty);
                c.WriteLine ("Server IP:   " + 
                        ((GamePrefs.GetString (EnumGamePrefs.ServerIP) != null && GamePrefs.GetString (EnumGamePrefs.ServerIP).Length != 0) ? GamePrefs.GetString (EnumGamePrefs.ServerIP) : "Any")
                );
                c.WriteLine ("Server port: " + GamePrefs.GetInt (EnumGamePrefs.ServerPort));
                c.WriteLine ("Max players: " + GamePrefs.GetInt (EnumGamePrefs.ServerMaxPlayerCount));
                c.WriteLine ("Game mode:   " + GamePrefs.GetString (EnumGamePrefs.GameMode));
                c.WriteLine ("World:       " + GamePrefs.GetString (EnumGamePrefs.GameWorld));
                c.WriteLine ("Game name:   " + GamePrefs.GetString (EnumGamePrefs.GameName));
                c.WriteLine ("Difficulty:  " + GamePrefs.GetInt (EnumGamePrefs.GameDifficulty));
                c.WriteLine (string.Empty);
                c.WriteLine ("Press 'help' to get a list of all commands. Press 'exit' to end session.");
                c.WriteLine (string.Empty);
        }

        private static string lineCorrecter (string line)
        {
                string res = "";
                for (int i = 0; i < line.Length; i++) {
                        if (line [i] >= ' ' && line [i] != '\'' && line [i] <= '~') {
                                res += line [i];
                        }
                }
                return res.Trim ();
        }

        public static void Disconnect ()
        {
                closed = true;
                if (listener != null) {
                        listener.Stop ();
                }
                foreach (Connection c in conns) {
                        c.Close ();
                }
                Thread.Sleep (100);
        }

        public static void SetConsole (cl004c console)
        {
                AllocsNetTelnetServer.console = console;
        }

        private static void RemoveClosedConnections ()
        {
                foreach (Connection c in conns) {
                        if (c.IsClosed ()) {
                                c.Close ();
                        }
                }
        }

        public static void WriteToClient (string line)
        {
                if (line == null) {
                        return;
                }
                RemoveClosedConnections ();
                foreach (Connection c in conns) {
                        if (c.IsAuthenticated())
                                c.WriteLine (line);
                }
        }
}