My own Mailinator in 5 minutes

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

using LumiSoft.Net.IO;
using LumiSoft.Net.TCP;
using LumiSoft.Net.UDP;
using LumiSoft.Net.SIP.Message;

namespace LumiSoft.Net.SIP.Stack
{
    /// <summary>
    /// Implements SIP Flow. Defined in draft-ietf-sip-outbound.
    /// </summary>
    /// <remarks>A Flow is a network protocol layer (layer 4) association
    ///  between two hosts that is represented by the network address and
    ///  port number of both ends and by the protocol.  For TCP, a flow is
    ///  equivalent to a TCP connection.  For UDP a flow is a bidirectional
    ///  stream of datagrams between a single pair of IP addresses and
    ///  ports of both peers.
    /// </remarks>
    public class SIP_Flow : IDisposable
    {
        private object       m_pLock           = new object();
        private bool         m_IsDisposed      = false;
        private bool         m_IsServer        = false;
        private SIP_Stack    m_pStack          = null;
        private TCP_Session  m_pTcpSession     = null;
        private DateTime     m_CreateTime;
        private string       m_ID              = "";
        private IPEndPoint   m_pLocalEP        = null;
        private IPEndPoint   m_pLocalPublicEP  = null;
        private IPEndPoint   m_pRemoteEP       = null;
        private string       m_Transport       = "";
        private DateTime     m_LastActivity;
        private DateTime     m_LastPing;
        private long         m_BytesWritten    = 0;
        private MemoryStream m_pMessage        = null;
        private bool         m_LastCRLF        = false;
        private TimerEx      m_pKeepAliveTimer = null;
        
        /// <summary>
        /// Default constructor.
        /// </summary>
        /// <param name="stack">Owner stack.</param>
        /// <param name="isServer">Specifies if flow is server or client flow.</param>
        /// <param name="localEP">Local IP end point.</param>
        /// <param name="remoteEP">Remote IP end point.</param>
        /// <param name="transport">SIP transport.</param>
        /// <exception cref="ArgumentNullException">Is raised when <b>stack</b>,<b>localEP</b>,<b>remoteEP</b>  or <b>transport</b> is null reference.</exception>
        /// <exception cref="ArgumentException">Is raised whena any of the arguments has invalid value.</exception>
        internal SIP_Flow(SIP_Stack stack,bool isServer,IPEndPoint localEP,IPEndPoint remoteEP,string transport)
        {
            if(stack == null){
                throw new ArgumentNullException("stack");
            }
            if(localEP == null){
                throw new ArgumentNullException("localEP");
            }
            if(remoteEP == null){
                throw new ArgumentNullException("remoteEP");
            }
            if(transport == null){
                throw new ArgumentNullException("transport");
            }

            m_pStack    = stack;
            m_IsServer  = isServer;
            m_pLocalEP  = localEP;
            m_pRemoteEP = remoteEP;
            m_Transport = transport.ToUpper();

            m_CreateTime   = DateTime.Now;
            m_LastActivity = DateTime.Now;
            m_ID           = m_pLocalEP.ToString() + "-" + m_pRemoteEP.ToString() + "-" + m_Transport;
            m_pMessage     = new MemoryStream();
        }

        /// <summary>
        /// Server TCP,TLS constructor.
        /// </summary>
        /// <param name="stack">Owner stack.</param>
        /// <param name="session">TCP session.</param>
        /// <exception cref="ArgumentNullException">Is raised when <b>stack</b> or <b>session</b> is null reference.</exception>
        internal SIP_Flow(SIP_Stack stack,TCP_Session session)
        {
            if(stack == null){
                throw new ArgumentNullException("stack");
            }
            if(session == null){
                throw new ArgumentNullException("session");
            }

            m_pStack      = stack;
            m_pTcpSession = session;

            m_IsServer     = true;            
            m_pLocalEP     = session.LocalEndPoint;
            m_pRemoteEP    = session.RemoteEndPoint;
            m_Transport    = session.IsSecureConnection ? SIP_Transport.TLS : SIP_Transport.TCP;
            m_CreateTime   = DateTime.Now;
            m_LastActivity = DateTime.Now;
            m_ID           = m_pLocalEP.ToString() + "-" + m_pRemoteEP.ToString() + "-" + m_Transport;
            m_pMessage     = new MemoryStream();

            BeginReadHeader();
        }


        #region mehtod Dispose

        /// <summary>
        /// Cleans up any resources being used.
        /// </summary>
        public void Dispose()
        {
            lock(m_pLock){
                if(m_IsDisposed){
                    return;
                }     
                OnDisposing();
                m_IsDisposed = true;

                if(m_pTcpSession != null){
                    m_pTcpSession.Dispose();
                    m_pTcpSession = null;
                }
                m_pMessage = null;
                if(m_pKeepAliveTimer != null){
                    m_pKeepAliveTimer.Dispose();
                    m_pKeepAliveTimer = null;
                }
            }
        }

        #endregion


        #region method Send

        /// <summary>
        /// Sends specified request to flow remote end point.
        /// </summary>
        /// <param name="request">SIP request to send.</param>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this method is accessed.</exception>
        /// <exception cref="ArgumentNullException">Is raised when <b>request</b> is null reference.</exception>
        public void Send(SIP_Request request)
        {
            lock(m_pLock){
                if(m_IsDisposed){
                    throw new ObjectDisposedException(this.GetType().Name);
                }
                if(request == null){
                    throw new ArgumentNullException("request");
                }

                SendInternal(request.ToByteData());
            }
        }

        /// <summary>
        /// Sends specified response to flow remote end point.
        /// </summary>
        /// <param name="response">SIP response to send.</param>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this method is accessed.</exception>
        /// <exception cref="ArgumentNullException">Is raised when <b>response</b> is null reference.</exception>
        public void Send(SIP_Response response)
        {
            lock(m_pLock){
                if(m_IsDisposed){
                    throw new ObjectDisposedException(this.GetType().Name);
                }
                if(response == null){
                    throw new ArgumentNullException("response");
                }

                SendInternal(response.ToByteData());
                m_LastPing = DateTime.Now;
            }
        }

        #endregion

        #region method SendPing

        /// <summary>
        /// Send ping request to flow remote end point.
        /// </summary>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this method is accessed.</exception>
        public void SendPing()
        {
            lock(m_pLock){
                if(m_IsDisposed){
                    throw new ObjectDisposedException(this.GetType().Name);
                }

                // Log:
                if(m_pStack.TransportLayer.Stack.Logger != null){
                    m_pStack.TransportLayer.Stack.Logger.AddWrite("",null,2,"Flow [id='" + this.ID + "'] sent \"ping\"",this.LocalEP,this.RemoteEP);
                }

                SendInternal(new byte[]{(byte)'\r',(byte)'\n',(byte)'\r',(byte)'\n'});
            }
        }

        #endregion


        #region method Start

        /// <summary>
        /// Starts flow processing.
        /// </summary>
        internal void Start()
        {        
            // Move processing to thread pool.
            AutoResetEvent startLock = new AutoResetEvent(false);
            ThreadPool.QueueUserWorkItem(new WaitCallback(delegate(object state){
                lock(m_pLock){
                    startLock.Set();

                    // TCP / TLS client, connect to remote end point.
                    if(!m_IsServer && m_Transport != SIP_Transport.UDP){
                        try{
                            TCP_Client client = new TCP_Client();
                            client.Connect(m_pLocalEP,m_pRemoteEP,m_Transport == SIP_Transport.TLS);

                            m_pTcpSession = client;

                            BeginReadHeader();
                        }
                        catch{
                            Dispose();
                        }
                    }
                }                
            }));
            startLock.WaitOne();
            startLock.Close();
        }

        #endregion


        #region method SendInternal

        /// <summary>
        /// Sends specified data to the remote end point.
        /// </summary>
        /// <param name="data">Data to send.</param>
        /// <exception cref="ArgumentNullException">Is raised when <b>data</b> is null reference.</exception>
        internal void SendInternal(byte[] data)
        {
            if(data == null){
                throw new ArgumentNullException("data");
            }
                        
            try{
                if(m_Transport == SIP_Transport.UDP){
                    m_pStack.TransportLayer.UdpServer.SendPacket(m_pLocalEP,data,0,data.Length,m_pRemoteEP);
                }
                else if(m_Transport == SIP_Transport.TCP){
                    m_pTcpSession.TcpStream.Write(data,0,data.Length);
                }
                else if(m_Transport == SIP_Transport.TLS){
                    m_pTcpSession.TcpStream.Write(data,0,data.Length);
                }                               

                m_BytesWritten += data.Length;
            }
            catch(IOException x){
                Dispose();

                throw x;
            }
        }

        #endregion


        #region method BeginReadHeader

        /// <summary>
        /// Starts reading SIP message header.
        /// </summary>
        private void BeginReadHeader()
        {            
            // Clear old data.
            m_pMessage.SetLength(0);

            // Start reading SIP message header.
            m_pTcpSession.TcpStream.BeginReadHeader(
                m_pMessage,
                m_pStack.TransportLayer.Stack.MaximumMessageSize,
                SizeExceededAction.JunkAndThrowException,
                new AsyncCallback(this.BeginReadHeader_Completed),
                null
            );
        }

        #endregion

        #region method BeginReadHeader_Completed

        /// <summary>
        /// This method is called when SIP message header reading has completed.
        /// </summary>
        /// <param name="asyncResult">An IAsyncResult that represents an asynchronous call.</param>
        private void BeginReadHeader_Completed(IAsyncResult asyncResult)
        {   
            try{
                int countStored = m_pTcpSession.TcpStream.EndReadHeader(asyncResult);
      
                // We got CRLF(ping or pong).
                if(countStored == 0){ 
                    // We have ping request.
                    if(this.IsServer){
                        // We have full ping request.
                        if(m_LastCRLF){
                            m_LastCRLF = false;

                            m_pStack.TransportLayer.OnMessageReceived(this,new byte[]{(byte)'\r',(byte)'\n',(byte)'\r',(byte)'\n'});
                        }
                        // We have first CRLF of ping request.
                        else{
                            m_LastCRLF = true;
                        }
                    }
                    // We got pong to our ping request.
                    else{
                        m_pStack.TransportLayer.OnMessageReceived(this,new byte[]{(byte)'\r',(byte)'\n'});
                    }

                    // Wait for new SIP message. 
                    BeginReadHeader();
                }
                // We have SIP message header.
                else{
                    m_LastCRLF = false;

                    // Add header terminator blank line.
                    m_pMessage.Write(new byte[]{(byte)'\r',(byte)'\n'},0,2);

                    m_pMessage.Position = 0;
                    string contentLengthValue = LumiSoft.Net.MIME.MIME_Utils.ParseHeaderField("Content-Length:",m_pMessage);
                    m_pMessage.Position = m_pMessage.Length;

                    int contentLength = 0;

                    // Read message body.
                    if(contentLengthValue != ""){
                        contentLength = Convert.ToInt32(contentLengthValue);
                    }

                    // Start reading message body.
                    if(contentLength > 0){
                        // Read body data.
                        m_pTcpSession.TcpStream.BeginReadFixedCount(m_pMessage,contentLength,new AsyncCallback(this.BeginReadData_Completed),null);
                    }
                    // Message with no body.
                    else{
                        byte[] messageData = m_pMessage.ToArray();
                        // Wait for new SIP message. 
                        BeginReadHeader();
                        
                        m_pStack.TransportLayer.OnMessageReceived(this,messageData);
                    }
                }
            }
            catch{
                Dispose();
            }
        }

        #endregion

        #region method BeginReadData_Completed

        /// <summary>
        /// This method is called when SIP message data reading has completed.
        /// </summary>
        /// <param name="asyncResult">An IAsyncResult that represents an asynchronous call.</param>
        private void BeginReadData_Completed(IAsyncResult asyncResult)
        {
            try{
                m_pTcpSession.TcpStream.EndReadFixedCount(asyncResult);

                byte[] messageData = m_pMessage.ToArray();
                // Wait for new SIP message. 
                BeginReadHeader();

                m_pStack.TransportLayer.OnMessageReceived(this,messageData);
            }
            catch{
                Dispose();
            }
        }

        #endregion


        #region method OnUdpPacketReceived

        /// <summary>
        /// This method is called when flow gets new UDP packet.
        /// </summary>
        /// <param name="e">Event data..</param>
        /// <exception cref="ArgumentNullException">Is raised when <b>e</b> is null reference.</exception>
        internal void OnUdpPacketReceived(UDP_e_PacketReceived e)
        {
            if(e == null){
                throw new ArgumentNullException("e");
            }

            m_LastActivity = DateTime.Now;

            byte[] data = new byte[e.Count];
            Array.Copy(e.Buffer,data,e.Count);

            m_pStack.TransportLayer.OnMessageReceived(this,data);
        }

        #endregion


        #region Properties implementation

        /// <summary>
        /// Gets if this object is disposed.
        /// </summary>
        public bool IsDisposed
        {
            get{ return m_IsDisposed; }
        }

        /// <summary>
        /// Gets if this flow is server flow or client flow.
        /// </summary>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this property is accessed.</exception>
        public bool IsServer
        {
            get{ 
                if(m_IsDisposed){
                    throw new ObjectDisposedException(this.GetType().Name);
                }

                return m_IsServer; 
            }
        }

        /// <summary>
        /// Gets time when flow was created.
        /// </summary>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this property is accessed.</exception>
        public DateTime CreateTime
        {
            get{ 
                if(m_IsDisposed){
                    throw new ObjectDisposedException(this.GetType().Name);
                }

                return m_CreateTime; 
            }
        }

        /// <summary>
        /// Gets flow ID.
        /// </summary>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this property is accessed.</exception>
        public string ID
        {
            get{ 
                if(m_IsDisposed){
                    throw new ObjectDisposedException(this.GetType().Name);
                }
                
                return m_ID; 
            }
        }

        /// <summary>
        /// Gets flow local IP end point.
        /// </summary>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this property is accessed.</exception>
        public IPEndPoint LocalEP
        {
            get{ 
                if(m_IsDisposed){
                    throw new ObjectDisposedException(this.GetType().Name);
                }

                return m_pLocalEP; 
            }
        }

        /// <summary>
        /// Gets local EP what actually visible to <b>RemoteEP</b>. This value is different from <b>LocalEP</b> when stack is behind NAT.
        /// </summary>
        public IPEndPoint LocalPublicEP
        {
            get{
                if(m_IsDisposed){
                    throw new ObjectDisposedException(this.GetType().Name);
                }

                // We may not lock here, because dead lock will happen. Client transaction runs on thread pool threads.
                //lock(m_pLock){
                    if(m_pLocalPublicEP != null){
                        return m_pLocalPublicEP;
                    }
                    else{
                        m_pLocalPublicEP = this.LocalEP;

                        try{
                            AutoResetEvent completionWaiter = new AutoResetEvent(false);
                            // Create OPTIONS request
                            SIP_Request optionsRequest = m_pStack.CreateRequest(SIP_Methods.OPTIONS,new SIP_t_NameAddress("sip:ping@publicIP.com"),new SIP_t_NameAddress("sip:ping@publicIP.com"));
                            optionsRequest.MaxForwards = 0;
                            SIP_ClientTransaction optionsTransaction = m_pStack.TransactionLayer.CreateClientTransaction(this,optionsRequest,true);
                            optionsTransaction.ResponseReceived += new EventHandler<SIP_ResponseReceivedEventArgs>(delegate(object s,SIP_ResponseReceivedEventArgs e){
                                SIP_t_ViaParm via = e.Response.Via.GetTopMostValue();       
                
                                IPEndPoint publicEP = new IPEndPoint(via.Received == null ? this.LocalEP.Address : via.Received,via.RPort > 0 ? via.RPort : this.LocalEP.Port);
                                // Set public EP port only if public IP is also different from local EP.
                                if(!this.LocalEP.Address.Equals(publicEP.Address)){
                                    m_pLocalPublicEP = publicEP;
                                }

                                completionWaiter.Set();
                            });
                            optionsTransaction.StateChanged += new EventHandler(delegate(object s,EventArgs e){
                                if(optionsTransaction.State == SIP_TransactionState.Terminated){                 
                                    completionWaiter.Set();
                                }
                            });
                            optionsTransaction.Start();
                 
                            // Wait OPTIONS request to complete.
                            completionWaiter.WaitOne();
                            completionWaiter.Close();
                        }
                        catch{
                        }

                        return m_pLocalPublicEP;
                    }
               // }
            }
        }

        /// <summary>
        /// Gets flow remote IP end point.
        /// </summary>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this property is accessed.</exception>
        public IPEndPoint RemoteEP
        {
            get{ 
                if(m_IsDisposed){
                    throw new ObjectDisposedException(this.GetType().Name);
                }

                return m_pRemoteEP; 
            }
        }

        /// <summary>
        /// Gets flow transport.
        /// </summary>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this property is accessed.</exception>
        public string Transport
        {
            get{ 
                if(m_IsDisposed){
                    throw new ObjectDisposedException(this.GetType().Name);
                }

                return m_Transport; 
            }
        }

        /// <summary>
        /// Gets if flow is reliable transport.
        /// </summary>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this property is accessed.</exception>
        public bool IsReliable
        {
            get{ 
                if(m_IsDisposed){
                    throw new ObjectDisposedException(this.GetType().Name);
                }

                return m_Transport != SIP_Transport.UDP; 
            }
        }

        /// <summary>
        /// Gets if this connection is secure.
        /// </summary>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this property is accessed.</exception>
        public bool IsSecure
        {
            get{
                if(m_IsDisposed){
                    throw new ObjectDisposedException(this.GetType().Name);
                }

                if(m_Transport == SIP_Transport.TLS){
                    return true;
                }
                else{
                    return false; 
                }
            }
        }

        /// <summary>
        /// Gets or sets if flow sends keep-alive packets.
        /// </summary>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this property is accessed.</exception>
        public bool SendKeepAlives
        {
            get{ 
                if(m_IsDisposed){
                    throw new ObjectDisposedException(this.GetType().Name);
                }

                return m_pKeepAliveTimer != null; 
            }

            set{
                if(m_IsDisposed){
                    throw new ObjectDisposedException(this.GetType().Name);
                }

                if(value){
                    if(m_pKeepAliveTimer == null){
                        m_pKeepAliveTimer = new TimerEx(15000,true);
                        m_pKeepAliveTimer.Elapsed += delegate(object s,System.Timers.ElapsedEventArgs e){  
                            try{
                                // Log:
                                if(m_pStack.TransportLayer.Stack.Logger != null){
                                    m_pStack.TransportLayer.Stack.Logger.AddWrite("",null,2,"Flow [id='" + this.ID + "'] sent \"ping\"",this.LocalEP,this.RemoteEP);
                                }

                                SendInternal(new byte[]{(byte)'\r',(byte)'\n',(byte)'\r',(byte)'\n'});
                            }
                            catch{
                                // We don't care about errors here.
                            }
                        };
                        m_pKeepAliveTimer.Enabled = true;
                    }
                }
                else{
                    if(m_pKeepAliveTimer != null){
                        m_pKeepAliveTimer.Dispose();
                        m_pKeepAliveTimer = null;
                    }
                }
            }
        }

        /// <summary>
        /// Gets when flow had last(send or receive) activity.
        /// </summary>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this property is accessed.</exception>
        public DateTime LastActivity
        {
            get{
                if(m_IsDisposed){
                    throw new ObjectDisposedException(this.GetType().Name);
                }

                if(m_Transport == SIP_Transport.TCP || m_Transport == SIP_Transport.TLS){
                    return m_pTcpSession.LastActivity;
                }
                else{
                    return m_LastActivity; 
                }
            }
        }

        /// <summary>
        /// Gets time when last ping request was sent.
        /// </summary>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this property is accessed.</exception>
        public DateTime LastPing
        {
            get{
                if(m_IsDisposed){
                    throw new ObjectDisposedException(this.GetType().Name);
                }

                return m_LastPing;
            }
        }

        // TODO: BytesReaded

        /// <summary>
        /// Gets how many bytes this flow has sent to remote party.
        /// </summary>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this property is accessed.</exception>
        public long BytesWritten
        {
            get{
                if(m_IsDisposed){
                    throw new ObjectDisposedException(this.GetType().Name);
                }

                return m_BytesWritten; 
            }
        }

        #endregion

        #region Events implementation

        /// <summary>
        /// Is raised when flow is disposing.
        /// </summary>
        public event EventHandler IsDisposing = null;

        #region method OnDisposing

        /// <summary>
        /// Raises <b>Disposed</b> event.
        /// </summary>
        private void OnDisposing()
        {
            if(this.IsDisposing != null){
                this.IsDisposing(this,new EventArgs());
            }
        }

        #endregion.

        #endregion

    }
}