public Dictionary<string, UserInfo> users = new Dictionary<string, UserInfo>();

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net.Sockets;
using System.Net.Security;
using System.Security.Authentication;
using System.IO;
using System.Threading;
using MySql.Data.MySqlClient;

namespace GarkServer
{
public class Client
{
    public Client(Program p, TcpClient c)
    {
        prog = p;
        client = c;

        // Handle client in another thread.
        (new Thread(new ThreadStart(SetupConn))).Start();
    }
    public static string Base64Encode(string plainText)
    {
        var plainTextBytes = System.Text.Encoding.UTF8.GetBytes(plainText);
        return System.Convert.ToBase64String(plainTextBytes);
    }
    public static string Base64Decode(string base64EncodedData)
    {
        var base64EncodedBytes = System.Convert.FromBase64String(base64EncodedData);
        return System.Text.Encoding.UTF8.GetString(base64EncodedBytes);
    }

    Program prog;
    public TcpClient client;
    public NetworkStream netStream;  // raw-data stream of connection.
    public SslStream ssl;            // encrypts connection using SSL.
    public BinaryReader br;
    public BinaryWriter bw;

    UserInfo userInfo;  // info about current user.

    void SetupConn()  // setup connection / login
    {
        var dbCon = DBConnection.Instance();
        dbCon.DatabaseName = "dbName";
        try
        {

            netStream = client.GetStream();
            ssl = new SslStream(netStream, false);
            ssl.AuthenticateAsServer(prog.cert, false, SslProtocols.Tls, true);

            br = new BinaryReader(ssl, Encoding.UTF8);
            bw = new BinaryWriter(ssl, Encoding.UTF8);

            bw.Write(IM_Hello);
            bw.Flush();
            int hello = br.ReadInt32();
            if (hello == IM_Hello)
            {
                byte logMode = br.ReadByte();
                string userName = br.ReadString();
                string password = br.ReadString();
                string ipadresa = br.ReadString();
                if (userName.Length < 32 || userName.Length > 4)
                {
                    if (password.Length < 512 || password.Length > 4)
                    {
                        if (logMode == IM_Login)
                        {
                            if (dbCon.IsConnect())
                            {

                                string query = "SELECT COUNT(id) FROM users WHERE username = '" + userName.ToLower() + "'";
                                using (MySqlCommand check_User_Name = new MySqlCommand(query, dbCon.Connection))
                                {
                                    int UserExist = Convert.ToInt32(check_User_Name.ExecuteScalar());
                                    if (UserExist == 1)
                                    {
                                        string query1 = "SELECT password,value1,apponline FROM users WHERE username='" + userName.ToLower() + "'";
                                        using (MySqlCommand cmd = new MySqlCommand(query1, dbCon.Connection))
                                        {
                                            MySqlDataReader reader = cmd.ExecuteReader();
                                            reader.Read();
                                            string gm_password = (string)reader["password"];
                                            string gm_value1 = (string)reader["im_value1"];
                                            bool gm_LoggedIn = (bool)reader["apponline"];
                                            reader.Close();

                                            if (password == gm_password)
                                            {
                                                UserInfo ucheck;
                                                if (prog.users.TryGetValue(userName.ToLower(), out ucheck))
                                                {
                                                    if (ucheck.LoggedIn)
                                                    {
                                                        // disconnect already connected client with same useranem
                                                        ucheck.Connection.CloseConn();
                                                        string query200 = "UPDATE users SET apponline='0' WHERE username='" + userName.ToLower() + "'";
                                                        using (MySqlCommand cmd5 = new MySqlCommand(query200, dbCon.Connection))
                                                        {
                                                            MySqlDataReader reader1 = cmd5.ExecuteReader();
                                                            reader1.Read();
                                                            reader1.Close();
                                                        }
                                                    }
                                                }

                                                userInfo = new UserInfo(userName.ToLower(), Base64Encode(password), this);
                                                prog.users.Add(userName.ToLower(), userInfo);

                                                var dateValue = DateTime.Now;
                                                string dateMysql = dateValue.ToString("yyyy-MM-dd HH:mm:ss");
                                                string query201 = "UPDATE users SET ipadresav4='" + ipadresa + "',apponline='1',webdt='" + dateMysql + "' WHERE username='" + userName.ToLower() + "'";
                                                using (MySqlCommand cmd111 = new MySqlCommand(query201, dbCon.Connection))
                                                {
                                                    MySqlDataReader reader2 = cmd111.ExecuteReader();
                                                    reader2.Read();
                                                    reader2.Close();

                                                    userInfo.Connection = this;
                                                    userInfo.LoggedIn = true;
                                                    bw.Write(IM_OK);
                                                    bw.Flush();
                                                    Receiver();

                                                }
                                            }
                                            else
                                                bw.Write(IM_WrongPass);
                                        }
                                    }
                                    else
                                        bw.Write(IM_NoExists);
                                }
                            }
                            else
                                Console.WriteLine("[{0}] MySQL Disconnected!", DateTime.Now);
                        }
                    }
                    else
                        bw.Write(IM_TooPassword);
                }
                else
                    bw.Write(IM_TooUsername);
            }
            CloseConn();
        }
        catch { CloseConn(); }
    }
    void CloseConn() // Close connection.
    {
        try
        {
            string userConnected = userInfo.UserName;
            var dbCon = DBConnection.Instance();
            dbCon.DatabaseName = "dbName";

            var dateValue = DateTime.Now;
            string dateMysql = dateValue.ToString("yyyy-MM-dd HH:mm:ss");
            string query7 = "UPDATE users SET apponline='0',webdt='" + dateMysql + "' WHERE username='" + userConnected.ToLower() + "'";
            using (MySqlCommand cmd = new MySqlCommand(query7, dbCon.Connection))
            {
                MySqlDataReader reader = cmd.ExecuteReader();
                reader.Read();
                reader.Close();
            }

            userInfo.LoggedIn = false;
            prog.users.Remove(userConnected.ToLower());
            br.Close();
            bw.Close();
            ssl.Close();
            netStream.Close();
            client.Close();
        }
        catch { }
    }
    void Receiver()
    {
        var dbCon = DBConnection.Instance();
        dbCon.DatabaseName = "dbName";
        userInfo.LoggedIn = true;

        try
        {
            while (client.Client.Connected)  // while user is connected
            {
                byte type = br.ReadByte();  // incoming packet type.

                if (type == IM_IsAvailable)
                {
                    // chat form packet to check if user is online
                    string who = br.ReadString();

                    bw.Write(IM_IsAvailable);
                    bw.Write(who);

                    UserInfo info;
                    if (prog.users.TryGetValue(who.ToLower(), out info))
                    {
                        if (info.LoggedIn)
                        {
                            bw.Write(true);
                        }
                        else
                            bw.Write(false);
                    }
                    else
                        bw.Write(false);
                    bw.Flush();
                }

                else if (type == IM_Send)
                {
                    // chat form send message
                    string to = br.ReadString();
                    string msg = br.ReadString();
                    UserInfo recipient;
                    if (prog.users.TryGetValue(to.ToLower(), out recipient))
                    {
                        // recipient logged in?
                        if (recipient.LoggedIn) // if yes
                        {
                            // send chat form opener packet
                            recipient.Connection.bw.Write(IM_Newmsg);
                            recipient.Connection.bw.Write(userInfo.UserName.ToLower());
                            recipient.Connection.bw.Flush();

                            // then send a message
                            recipient.Connection.bw.Write(IM_Received);
                            recipient.Connection.bw.Write(userInfo.UserName.ToLower());  // From
                            recipient.Connection.bw.Write(msg);
                            recipient.Connection.bw.Flush();
                        }
                    }
                }

                else if (type == IM_Online)
                {
                    // timer every 10 sec to set "i'm online" checkin time and to fetch friends
                    string u_id;
                    string f_id;
                    string f_username;
                    string f_displayname;
                    string f_webstatus;
                    string f_checkin;
                    bool f_apponline;

                    string who = br.ReadString();

                    var dateValue = DateTime.Now;
                    string dateMysql = dateValue.ToString("yyyy-MM-dd HH:mm:ss");
                    string query100 = "UPDATE users SET checkin='" + dateMysql + "' WHERE username='" + who.ToLower() + "'";
                    using (MySqlCommand cmd100 = new MySqlCommand(query100, dbCon.Connection))
                    {
                        MySqlDataReader reader = cmd100.ExecuteReader();
                        reader.Read();
                        reader.Close();
                    }

                    string query1 = "SELECT id FROM users WHERE username='" + who.ToLower() + "' ";
                    using (MySqlCommand cmd1 = new MySqlCommand(query1, dbCon.Connection))
                    {
                        using (var reader1 = cmd1.ExecuteReader())
                        {
                            reader1.Read();
                            u_id = reader1.GetString("id");
                            reader1.Close();

                            string query2 = "SELECT a.friend,b.username,b.displayname,b.webstatus,b.apponline,b.checkin FROM friends a JOIN users b on b.id = a.friend WHERE a.user = " + u_id + "";
                            using (MySqlCommand cmd0 = new MySqlCommand(query2, dbCon.Connection))
                            {
                                using (var reader = cmd0.ExecuteReader())
                                {
                                    while (reader.Read())
                                    {
                                        f_id = reader.GetString("friend");
                                        f_username = reader.GetString("username");
                                        f_displayname = reader.GetString("displayname");
                                        f_webstatus = reader.GetString("webstatus");
                                        f_apponline = reader.GetBoolean("apponline");
                                        f_checkin = reader.GetString("checkin");
                                        DateTime now = DateTime.Now;

                                        DateTime myDate;
                                        DateTime.TryParse(f_checkin, out myDate);
                                        var diffInSeconds = (DateTime.Now - myDate).TotalSeconds;

                                        UserInfo info;
                                        if (prog.users.TryGetValue(f_username.ToLower(), out info) && diffInSeconds < 21)
                                        {
                                            if (info.LoggedIn)
                                            {
                                                // if friend is ONLINE
                                                bw.Write(IM_Here);
                                                bw.Write(true);
                                                bw.Write(f_username);
                                                bw.Write(f_displayname);
                                                bw.Write(f_webstatus);
                                                bw.Flush();
                                            }
                                        }
                                        else
                                        {
                                            // else friend is OFFLINE
                                            bw.Write(IM_Here);
                                            bw.Write(false);
                                            bw.Write(f_username);
                                            bw.Write(f_displayname);
                                            bw.Write(f_webstatus);
                                            bw.Flush();
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
            }
        }
        catch (IOException) { }

        userInfo.LoggedIn = false;
    }

    public const int IM_Hello = 2016;      // Check Connection
    public const byte IM_OK = 0;           // Connection OK
    public const byte IM_Login = 1;        // Login
    public const byte IM_Register = 2;     // Register - disabled because i don't need it
    public const byte IM_TooUsername = 3;  // Too long username
    public const byte IM_TooPassword = 4;  // Too long password
    public const byte IM_Exists = 5;       // Already exists
    public const byte IM_NoExists = 6;     // Doesn't exists
    public const byte IM_WrongPass = 7;    // Wrong password
    public const byte IM_IsAvailable = 8;  // Is user available?
    public const byte IM_Send = 9;         // Send message
    public const byte IM_Received = 10;    // Message received
    public const byte IM_Online = 11;      // Receive "I'm Online" packet and sends Friends status (offline/online) to clients
    public const byte IM_Here = 12;        // Get "I'm Here" user info from server
    public const byte IM_Newmsg = 13;      // Chat form opener packet
}
}

[Serializable]
public class UserInfo
{
    public string UserName;
    public string Password;
    [NonSerialized] public bool LoggedIn;      // is logged in and connected?
    [NonSerialized] public Client Connection;  // connection info

    public UserInfo(string user, string pass)
    {
        this.UserName = user;
        this.Password = pass;
        this.LoggedIn = false;
    }
    public UserInfo(string user, string pass, Client conn)
    {
        this.UserName = user;
        this.Password = pass;
        this.LoggedIn = true;
        this.Connection = conn;
    }
}