/Sparkles/TcpListener.cs

//   SparkleShare, a collaboration and sharing tool.
//   Copyright (C) 2010  Hylke Bons <hi@planetpeanut.uk>
//
//   This program is free software: you can redistribute it and/or modify
//   it under the terms of the GNU Lesser General Public License as 
//   published by the Free Software Foundation, either version 3 of the 
//   License, or (at your option) any later version.
//
//   This program is distributed in the hope that it will be useful,
//   but WITHOUT ANY WARRANTY; without even the implied warranty of
//   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
//   GNU General Public License for more details.
//
//   You should have received a copy of the GNU General Public License
//   along with this program. If not, see <http://www.gnu.org/licenses/>.


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

namespace Sparkles {

    public class TcpListener : BaseListener {

        private Socket socket;
        private Thread thread;
        private bool is_connected  = false;
        private bool is_connecting = false;
        private DateTime last_ping = DateTime.Now;


        public TcpListener (Uri server, string folder_identifier) : base (server, folder_identifier)
        {
        }


        public override bool IsConnected {
            get {
                return this.is_connected;
            }
        }


        public override bool IsConnecting {
            get {
                return this.is_connecting;
            }
        }


        // Starts a new thread and listens to the channel
        public override void Connect ()
        {
            this.is_connecting = true;

            this.thread = new Thread (() => {
                int port = Server.Port;

                if (port < 0)
                    port = 443;

                try {
                    this.socket = new Socket (AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp) {
                        ReceiveTimeout = 5 * 1000,
                        SendTimeout    = 5 * 1000
                    };

                    // Try to connect to the server
                    this.socket.Connect (Server.Host, port);

                    this.is_connecting = false;
                    this.is_connected  = true;

                    OnConnected ();

                } catch (Exception e) {
                    this.is_connected  = false;
                    this.is_connecting = false;

                    if (this.socket != null)
                        this.socket.Close ();

                    OnDisconnected (Sparkles.DisconnectReason.TimeOut, e.Message);
                    return;
                }


                byte [] bytes  = new byte [4096];
                int bytes_read = 0;
                this.last_ping = DateTime.Now;

                // Wait for messages
                while (this.is_connected) {
                    try {
                        int i = 0;
                        int timeout = 300;
                        DisconnectReason reason = DisconnectReason.TimeOut;

                        // This blocks the thread
                        while (this.socket.Available < 1) {
                            try {
                                // We've timed out, let's ping the server to
                                // see if the connection is still up
                                if (i == timeout) {
                                    Logger.LogInfo ("ListenerTcp", "Pinging " + Server);

                                    byte [] ping_bytes = Encoding.UTF8.GetBytes ("ping\n");
                                    byte [] pong_bytes = new byte [4096];

                                    this.socket.Send (ping_bytes);

                                    if (this.socket.Receive (pong_bytes) < 1)
                                        // 10057 means "Socket is not connected"
                                        throw new SocketException (10057);

                                    Logger.LogInfo ("ListenerTcp", "Received pong from " + Server);

                                    i = 0;
                                    this.last_ping = DateTime.Now;

                                } else {

                                    // Check when the last ping occured. If it's
                                    // significantly longer than our regular interval the
                                    // system likely woke up from sleep and we want to
                                    // simulate a disconnect
                                    int sleepiness = DateTime.Compare (
                                        this.last_ping.AddMilliseconds (timeout * 1000 * 1.2),
                                        DateTime.Now
                                    );

                                    if (sleepiness <= 0) {
                                        Logger.LogInfo ("ListenerTcp", "System woke up from sleep");
                                        reason = DisconnectReason.SystemSleep;

                                        // 10057 means "Socket is not connected"
                                        throw new SocketException (10057);
                                    }
                                }

                            // The ping failed: disconnect completely
                            } catch (SocketException e) {
                                Disconnect(reason, "Ping timeout: " + e.Message);
                                return;
                            }

                            Thread.Sleep (1000);
                            i++;
                        }

                    } catch (Exception) {
                        return;
                    }

                    try {
                        if (this.socket.Available > 0)
                            bytes_read = this.socket.Receive (bytes);

                        // Parse the received message
                        if (bytes_read > 0) {
                            string received = Encoding.UTF8.GetString (bytes);
                            string line     = received.Substring (0, received.IndexOf ("\n"));

                            if (!line.Contains ("!"))
                                continue;

                            string folder_identifier = line.Substring (0, line.IndexOf ("!"));
                            string message           = CleanMessage (line.Substring (line.IndexOf ("!") + 1));

                            // We have a message!
                            if (!folder_identifier.Equals ("debug") && !string.IsNullOrEmpty (message))
                                OnAnnouncement (new Announcement (folder_identifier, message));
                        }

                    } catch (SocketException e) {
                        Disconnect (DisconnectReason.TimeOut, "Timeout during receiving: " + e.Message);
                        return;
                    }
                }
            });

            this.thread.Start ();
        }


        private void Disconnect (DisconnectReason reason, string message)
        {
            this.is_connected  = false;
            this.is_connecting = false;

            if (this.socket != null) {
                this.socket.Close ();
                this.socket = null;
            }

            OnDisconnected (reason, message);
        }


        protected override void AlsoListenToInternal (string folder_identifier)
        {
            string to_send = "subscribe " + folder_identifier + "\n";

            try {
                this.socket.Send (Encoding.UTF8.GetBytes (to_send));
                this.last_ping = DateTime.Now;

            } catch (Exception e) {
                this.is_connected  = false;
                this.is_connecting = false;

                OnDisconnected (DisconnectReason.TimeOut, e.Message);
            }
        }


        protected override void AnnounceInternal (Announcement announcement)
        {
            string to_send = "announce " + announcement.FolderIdentifier + " " + announcement.Message + "\n";

            try {
                if (this.socket != null)
                    this.socket.Send (Encoding.UTF8.GetBytes (to_send));

                this.last_ping = DateTime.Now;

            } catch (Exception e) {
                this.is_connected  = false;
                this.is_connecting = false;

                OnDisconnected (DisconnectReason.TimeOut, e.Message);
            }
        }


        public override void Dispose ()
        {
            if (this.socket != null) {
                this.socket.Close ();
                this.socket = null;
            }

            this.thread.Abort ();
            this.thread.Join ();

            base.Dispose ();
        }


        private string CleanMessage (string message)
        {
            message = message.Replace ("\n", "");
            message = message.Replace ("\0", "");
            return message.Trim ();
        }
    }
}