SocketCache.cs source code in C# .NET

Source code for the .NET framework in C#

                        

Code:

/ 4.0 / 4.0 / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / clr / src / ManagedLibraries / Remoting / Channels / CORE / SocketCache.cs / 1305376 / SocketCache.cs

                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
//==========================================================================
//  File:       SocketCache.cs 
// 
//  Summary:    Cache for client sockets.
// 
//=========================================================================


using System; 
using System.Collections;
using System.Net; 
using System.Net.Sockets; 
using System.Runtime.Remoting;
using System.Runtime.Remoting.Channels; 
using System.Threading;


namespace System.Runtime.Remoting.Channels 
{
 
    // Delegate to method that will fabricate the appropriate socket handler 
    internal delegate SocketHandler SocketHandlerFactory(Socket socket,
                                                         SocketCache socketCache, 
                                                         String machineAndPort);


    // Used to cache client connections to a single port on a server 
    internal class RemoteConnection
    { 
        private static char[] colonSep = new char[]{':'}; 

        private CachedSocketList _cachedSocketList; 

        // reference back to the socket cache
        private SocketCache _socketCache;
 
        // remote endpoint data
        private String     _machineAndPort; 
        private IPAddress[] _addressList; 
        private int _port;
        private EndPoint _lkgIPEndPoint; 
        private bool connectIPv6 = false;
        private Uri _uri;

 
        internal RemoteConnection(SocketCache socketCache, String machineAndPort)
        { 
            _socketCache = socketCache; 

            _cachedSocketList = new CachedSocketList(socketCache.SocketTimeout, 
                                                                        socketCache.CachePolicy);

            // parse "machinename:port", add a dummy scheme to get uri parsing
            _uri = new Uri("dummy://" + machineAndPort); 

            _port = _uri.Port; 
            _machineAndPort = machineAndPort; 

        } // RemoteConnection 


        internal SocketHandler GetSocket()
        { 
            // try the cached socket list
            SocketHandler socketHandler = _cachedSocketList.GetSocket(); 
            if (socketHandler != null) 
                return socketHandler;
 
            // Otherwise, we'll just create a new one.
            return CreateNewSocket();
        } // GetSocket
 
        internal void ReleaseSocket(SocketHandler socket)
        { 
            socket.ReleaseControl(); 
            _cachedSocketList.ReturnSocket(socket);
        } // ReleaseSocket 


        private bool HasIPv6Address(IPAddress[] addressList)
        { 
            foreach (IPAddress address in addressList)
            { 
                if (address.AddressFamily == AddressFamily.InterNetworkV6) 
                    return true;
            } 
            return false;
        }

        private void DisableNagleDelays(Socket socket) 
        {
            // disable nagle delays 
            socket.SetSocketOption(SocketOptionLevel.Tcp, 
                                   SocketOptionName.NoDelay,
                                   1); 
        }

        private SocketHandler CreateNewSocket()
        { 
            //
            // We should not cache the DNS result 
            // 
            _addressList = Dns.GetHostAddresses(_uri.Host);
            connectIPv6 = Socket.OSSupportsIPv6 && HasIPv6Address(_addressList); 

            // If there is only one entry in the list, just use that
            // we will fail if the connect on it fails
            if (_addressList.Length == 1) 
                    return CreateNewSocket(new IPEndPoint(_addressList[0], _port));
 
            // If LKG is set try using that 
            if (_lkgIPEndPoint != null)
            { 
                try{
                    return CreateNewSocket(_lkgIPEndPoint);
                }
                catch (Exception) { 
                    // Since this fail null out LKG
                    _lkgIPEndPoint = null; 
                } 
            }
 
            // If IPv6 is enabled try connecting to IP addresses
            if (connectIPv6)
            {
                try{ 
                    return CreateNewSocket(AddressFamily.InterNetworkV6);
                }catch (Exception) {} 
            } 

            // If everything fails try ipv4 addresses 
            return CreateNewSocket(AddressFamily.InterNetwork);

        }
 
        private SocketHandler CreateNewSocket(EndPoint ipEndPoint)
        { 
            Socket socket = new Socket(ipEndPoint.AddressFamily, 
                                       SocketType.Stream,
                                       ProtocolType.Tcp); 

            DisableNagleDelays(socket);
            InternalRemotingServices.RemotingTrace("RemoteConnection::CreateNewSocket: connecting new socket :: " + ipEndPoint);
 
            socket.Connect(ipEndPoint);
            _lkgIPEndPoint = socket.RemoteEndPoint; 
            return _socketCache.CreateSocketHandler(socket, _machineAndPort); 
        } // CreateNewSocket
 
        private SocketHandler CreateNewSocket(AddressFamily family)
        {
            Socket socket = new Socket(family,
                                       SocketType.Stream, 
                                       ProtocolType.Tcp);
 
            DisableNagleDelays(socket); 

            socket.Connect(_addressList, _port); 
            _lkgIPEndPoint = socket.RemoteEndPoint;
            return _socketCache.CreateSocketHandler(socket, _machineAndPort);
        } // CreateNewSocket
 

        internal void TimeoutSockets(DateTime currentTime) 
        { 
            _cachedSocketList.TimeoutSockets(currentTime, _socketCache.SocketTimeout);
        } // TimeoutSockets 



    } // class RemoteConnection 

 
 
    internal class CachedSocket
    { 
        private SocketHandler _socket;
        private DateTime _socketLastUsed;

        private CachedSocket _next; 

        internal CachedSocket(SocketHandler socket, CachedSocket next) 
        { 
            _socket = socket;
            _socketLastUsed = DateTime.UtcNow; 
            _next = next;
        } // CachedSocket

        internal SocketHandler Handler { get { return _socket; } } 
        internal DateTime LastUsed { get { return _socketLastUsed; } }
 
        internal CachedSocket Next 
        {
            get { return _next; } 
            set { _next = value; }
        }

    } // class CachedSocket 

 
    internal class CachedSocketList 
    {
        private int _socketCount; 
        private TimeSpan _socketLifetime;
        private SocketCachePolicy _socketCachePolicy;
        private CachedSocket _socketList; // linked list
 
        internal CachedSocketList(TimeSpan socketLifetime, SocketCachePolicy socketCachePolicy)
        { 
            _socketCount = 0; 
            _socketLifetime = socketLifetime;
            _socketCachePolicy = socketCachePolicy; 
            _socketList = null;
        } // CachedSocketList

 
        internal SocketHandler GetSocket()
        { 
            if (_socketCount == 0) 
                return null;
 
            lock (this)
            {
                if (_socketList != null)
                { 
                    SocketHandler socket = _socketList.Handler;
                    _socketList = _socketList.Next; 
 
                    bool bRes = socket.----ForControl();
 
                    // We should always have control since there shouldn't
                    //   be contention here.
                    InternalRemotingServices.RemotingAssert(bRes, "someone else has the socket?");
 
                    _socketCount--;
                    return socket; 
                } 
            }
 
            return null;
        } // GetSocket

 
        internal void ReturnSocket(SocketHandler socket)
        { 
            TimeSpan socketActiveTime = DateTime.UtcNow - socket.CreationTime; 
            bool closeSocket = false;
            lock (this) 
            {
                // Check if socket active time has exceeded the lifetime
                // If it has just close the Socket
                if (_socketCachePolicy != SocketCachePolicy.AbsoluteTimeout || 
                    socketActiveTime < _socketLifetime)
                { 
                    // Ignore duplicate entries for the same socket handler 
                    for (CachedSocket curr = _socketList; curr != null; curr = curr.Next){
                        if (socket == curr.Handler) 
                            return;
                    }

                    _socketList = new CachedSocket(socket, _socketList); 
                    _socketCount++;
                } 
                else 
                {
                    closeSocket = true; 
                }
            }
            if(closeSocket)
            { 
                socket.Close();
            } 
        } // ReturnSocket 

 
        internal void TimeoutSockets(DateTime currentTime, TimeSpan socketLifetime)
        {
           lock (this)
           { 
                CachedSocket prev = null;
                CachedSocket curr = _socketList; 
 
                while (curr != null)
                { 
                    // see if it's lifetime has expired
                    if ((_socketCachePolicy == SocketCachePolicy.AbsoluteTimeout && // This is for absolute
                            (currentTime - curr.Handler.CreationTime) > socketLifetime) ||
                        (currentTime - curr.LastUsed) > socketLifetime) // This is relative behaviour 
                    {
                        curr.Handler.Close(); 
 
                        // remove current cached socket from list
                        if (prev == null) 
                        {
                            // it's the first item, so update _socketList
                            _socketList = curr.Next;
                            curr = _socketList; 
                        }
                        else 
                        { 
                            // remove current item from the list
                            curr = curr.Next; 
                            prev.Next = curr;
                        }

                        // decrement socket count 
                        _socketCount--;
                    } 
                    else 
                    {
                        prev = curr; 
                        curr = curr.Next;
                    }
                }
            } 
        } // TimeoutSockets
 
 
    } // class CachedSocketList
 



 
    internal class SocketCache
    { 
        // collection of RemoteConnection's. 
        private static Hashtable _connections = new Hashtable();
 
        private SocketHandlerFactory _handlerFactory;

        // socket timeout data
        private static RegisteredWaitHandle _registeredWaitHandle; 
        private static WaitOrTimerCallback _socketTimeoutDelegate;
        private static AutoResetEvent _socketTimeoutWaitHandle; 
        private static TimeSpan _socketTimeoutPollTime = TimeSpan.FromSeconds(10); 
        private SocketCachePolicy _socketCachePolicy;
        private TimeSpan _socketTimeout; 
        private int _receiveTimeout = 0;


        static SocketCache() 
        {
            InitializeSocketTimeoutHandler(); 
        } 

        internal SocketCache(SocketHandlerFactory handlerFactory, SocketCachePolicy socketCachePolicy, 
                                                                        TimeSpan socketTimeout)
        {
            _handlerFactory = handlerFactory;
            _socketCachePolicy = socketCachePolicy; 
            _socketTimeout = socketTimeout;
        } // SocketCache 
 
        internal TimeSpan SocketTimeout { get { return _socketTimeout; } set { _socketTimeout = value;} }
        internal int ReceiveTimeout { get { return _receiveTimeout; } set { _receiveTimeout = value;} } 
        internal SocketCachePolicy CachePolicy { get { return _socketCachePolicy; } set { _socketCachePolicy = value;}}


        private static void InitializeSocketTimeoutHandler() 
        {
            _socketTimeoutDelegate = new WaitOrTimerCallback(TimeoutSockets); 
            _socketTimeoutWaitHandle = new AutoResetEvent(false); 
            _registeredWaitHandle =
                ThreadPool.UnsafeRegisterWaitForSingleObject( 
                    _socketTimeoutWaitHandle,
                    _socketTimeoutDelegate,
                    "TcpChannelSocketTimeout",
                    _socketTimeoutPollTime, 
                    true); // execute only once
        } // InitializeSocketTimeoutHandler 
 
        private static void TimeoutSockets(Object state, Boolean wasSignalled)
        { 
            DateTime currentTime = DateTime.UtcNow;

            lock (_connections)
            { 
                foreach (DictionaryEntry entry in _connections)
                { 
                    RemoteConnection connection = (RemoteConnection)entry.Value; 
                    connection.TimeoutSockets(currentTime);
                } 
            }

            _registeredWaitHandle.Unregister(null);
            _registeredWaitHandle = 
                ThreadPool.UnsafeRegisterWaitForSingleObject(
                    _socketTimeoutWaitHandle, 
                    _socketTimeoutDelegate, 
                    "TcpChannelSocketTimeout",
                    _socketTimeoutPollTime, 
                    true); // execute only once
        } // TimeoutSockets

 

        internal SocketHandler CreateSocketHandler(Socket socket, String machineAndPort) 
        { 
            socket.ReceiveTimeout = _receiveTimeout;
            return _handlerFactory(socket, this, machineAndPort); 
        }


        // The key is expected to of the form "machinename:port" 
        public SocketHandler GetSocket(String machinePortAndSid, bool openNew)
        { 
            RemoteConnection connection = (RemoteConnection)_connections[machinePortAndSid]; 
            if (openNew || connection == null)
            { 
                connection = new RemoteConnection(this, machinePortAndSid);

                // doesn't matter if different RemoteConnection's get written at
                //   the same time (GC will come along and close them). 
                lock (_connections)
                { 
                    _connections[machinePortAndSid] = connection; 
                }
            } 

            return connection.GetSocket();
        } // GetSocket
 
        public void ReleaseSocket(String machinePortAndSid, SocketHandler socket)
        { 
            RemoteConnection connection = (RemoteConnection)_connections[machinePortAndSid]; 
            if (connection != null)
            { 
                connection.ReleaseSocket(socket);
            }
            else
            { 
                // there should have been a connection, so let's just close
                //   this socket. 
                socket.Close(); 
            }
        } // ReleaseSocket 


    } // SocketCache
 

 
 
} // namespace System.Runtime.Remoting.Channels
 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
//==========================================================================
//  File:       SocketCache.cs 
// 
//  Summary:    Cache for client sockets.
// 
//=========================================================================


using System; 
using System.Collections;
using System.Net; 
using System.Net.Sockets; 
using System.Runtime.Remoting;
using System.Runtime.Remoting.Channels; 
using System.Threading;


namespace System.Runtime.Remoting.Channels 
{
 
    // Delegate to method that will fabricate the appropriate socket handler 
    internal delegate SocketHandler SocketHandlerFactory(Socket socket,
                                                         SocketCache socketCache, 
                                                         String machineAndPort);


    // Used to cache client connections to a single port on a server 
    internal class RemoteConnection
    { 
        private static char[] colonSep = new char[]{':'}; 

        private CachedSocketList _cachedSocketList; 

        // reference back to the socket cache
        private SocketCache _socketCache;
 
        // remote endpoint data
        private String     _machineAndPort; 
        private IPAddress[] _addressList; 
        private int _port;
        private EndPoint _lkgIPEndPoint; 
        private bool connectIPv6 = false;
        private Uri _uri;

 
        internal RemoteConnection(SocketCache socketCache, String machineAndPort)
        { 
            _socketCache = socketCache; 

            _cachedSocketList = new CachedSocketList(socketCache.SocketTimeout, 
                                                                        socketCache.CachePolicy);

            // parse "machinename:port", add a dummy scheme to get uri parsing
            _uri = new Uri("dummy://" + machineAndPort); 

            _port = _uri.Port; 
            _machineAndPort = machineAndPort; 

        } // RemoteConnection 


        internal SocketHandler GetSocket()
        { 
            // try the cached socket list
            SocketHandler socketHandler = _cachedSocketList.GetSocket(); 
            if (socketHandler != null) 
                return socketHandler;
 
            // Otherwise, we'll just create a new one.
            return CreateNewSocket();
        } // GetSocket
 
        internal void ReleaseSocket(SocketHandler socket)
        { 
            socket.ReleaseControl(); 
            _cachedSocketList.ReturnSocket(socket);
        } // ReleaseSocket 


        private bool HasIPv6Address(IPAddress[] addressList)
        { 
            foreach (IPAddress address in addressList)
            { 
                if (address.AddressFamily == AddressFamily.InterNetworkV6) 
                    return true;
            } 
            return false;
        }

        private void DisableNagleDelays(Socket socket) 
        {
            // disable nagle delays 
            socket.SetSocketOption(SocketOptionLevel.Tcp, 
                                   SocketOptionName.NoDelay,
                                   1); 
        }

        private SocketHandler CreateNewSocket()
        { 
            //
            // We should not cache the DNS result 
            // 
            _addressList = Dns.GetHostAddresses(_uri.Host);
            connectIPv6 = Socket.OSSupportsIPv6 && HasIPv6Address(_addressList); 

            // If there is only one entry in the list, just use that
            // we will fail if the connect on it fails
            if (_addressList.Length == 1) 
                    return CreateNewSocket(new IPEndPoint(_addressList[0], _port));
 
            // If LKG is set try using that 
            if (_lkgIPEndPoint != null)
            { 
                try{
                    return CreateNewSocket(_lkgIPEndPoint);
                }
                catch (Exception) { 
                    // Since this fail null out LKG
                    _lkgIPEndPoint = null; 
                } 
            }
 
            // If IPv6 is enabled try connecting to IP addresses
            if (connectIPv6)
            {
                try{ 
                    return CreateNewSocket(AddressFamily.InterNetworkV6);
                }catch (Exception) {} 
            } 

            // If everything fails try ipv4 addresses 
            return CreateNewSocket(AddressFamily.InterNetwork);

        }
 
        private SocketHandler CreateNewSocket(EndPoint ipEndPoint)
        { 
            Socket socket = new Socket(ipEndPoint.AddressFamily, 
                                       SocketType.Stream,
                                       ProtocolType.Tcp); 

            DisableNagleDelays(socket);
            InternalRemotingServices.RemotingTrace("RemoteConnection::CreateNewSocket: connecting new socket :: " + ipEndPoint);
 
            socket.Connect(ipEndPoint);
            _lkgIPEndPoint = socket.RemoteEndPoint; 
            return _socketCache.CreateSocketHandler(socket, _machineAndPort); 
        } // CreateNewSocket
 
        private SocketHandler CreateNewSocket(AddressFamily family)
        {
            Socket socket = new Socket(family,
                                       SocketType.Stream, 
                                       ProtocolType.Tcp);
 
            DisableNagleDelays(socket); 

            socket.Connect(_addressList, _port); 
            _lkgIPEndPoint = socket.RemoteEndPoint;
            return _socketCache.CreateSocketHandler(socket, _machineAndPort);
        } // CreateNewSocket
 

        internal void TimeoutSockets(DateTime currentTime) 
        { 
            _cachedSocketList.TimeoutSockets(currentTime, _socketCache.SocketTimeout);
        } // TimeoutSockets 



    } // class RemoteConnection 

 
 
    internal class CachedSocket
    { 
        private SocketHandler _socket;
        private DateTime _socketLastUsed;

        private CachedSocket _next; 

        internal CachedSocket(SocketHandler socket, CachedSocket next) 
        { 
            _socket = socket;
            _socketLastUsed = DateTime.UtcNow; 
            _next = next;
        } // CachedSocket

        internal SocketHandler Handler { get { return _socket; } } 
        internal DateTime LastUsed { get { return _socketLastUsed; } }
 
        internal CachedSocket Next 
        {
            get { return _next; } 
            set { _next = value; }
        }

    } // class CachedSocket 

 
    internal class CachedSocketList 
    {
        private int _socketCount; 
        private TimeSpan _socketLifetime;
        private SocketCachePolicy _socketCachePolicy;
        private CachedSocket _socketList; // linked list
 
        internal CachedSocketList(TimeSpan socketLifetime, SocketCachePolicy socketCachePolicy)
        { 
            _socketCount = 0; 
            _socketLifetime = socketLifetime;
            _socketCachePolicy = socketCachePolicy; 
            _socketList = null;
        } // CachedSocketList

 
        internal SocketHandler GetSocket()
        { 
            if (_socketCount == 0) 
                return null;
 
            lock (this)
            {
                if (_socketList != null)
                { 
                    SocketHandler socket = _socketList.Handler;
                    _socketList = _socketList.Next; 
 
                    bool bRes = socket.----ForControl();
 
                    // We should always have control since there shouldn't
                    //   be contention here.
                    InternalRemotingServices.RemotingAssert(bRes, "someone else has the socket?");
 
                    _socketCount--;
                    return socket; 
                } 
            }
 
            return null;
        } // GetSocket

 
        internal void ReturnSocket(SocketHandler socket)
        { 
            TimeSpan socketActiveTime = DateTime.UtcNow - socket.CreationTime; 
            bool closeSocket = false;
            lock (this) 
            {
                // Check if socket active time has exceeded the lifetime
                // If it has just close the Socket
                if (_socketCachePolicy != SocketCachePolicy.AbsoluteTimeout || 
                    socketActiveTime < _socketLifetime)
                { 
                    // Ignore duplicate entries for the same socket handler 
                    for (CachedSocket curr = _socketList; curr != null; curr = curr.Next){
                        if (socket == curr.Handler) 
                            return;
                    }

                    _socketList = new CachedSocket(socket, _socketList); 
                    _socketCount++;
                } 
                else 
                {
                    closeSocket = true; 
                }
            }
            if(closeSocket)
            { 
                socket.Close();
            } 
        } // ReturnSocket 

 
        internal void TimeoutSockets(DateTime currentTime, TimeSpan socketLifetime)
        {
           lock (this)
           { 
                CachedSocket prev = null;
                CachedSocket curr = _socketList; 
 
                while (curr != null)
                { 
                    // see if it's lifetime has expired
                    if ((_socketCachePolicy == SocketCachePolicy.AbsoluteTimeout && // This is for absolute
                            (currentTime - curr.Handler.CreationTime) > socketLifetime) ||
                        (currentTime - curr.LastUsed) > socketLifetime) // This is relative behaviour 
                    {
                        curr.Handler.Close(); 
 
                        // remove current cached socket from list
                        if (prev == null) 
                        {
                            // it's the first item, so update _socketList
                            _socketList = curr.Next;
                            curr = _socketList; 
                        }
                        else 
                        { 
                            // remove current item from the list
                            curr = curr.Next; 
                            prev.Next = curr;
                        }

                        // decrement socket count 
                        _socketCount--;
                    } 
                    else 
                    {
                        prev = curr; 
                        curr = curr.Next;
                    }
                }
            } 
        } // TimeoutSockets
 
 
    } // class CachedSocketList
 



 
    internal class SocketCache
    { 
        // collection of RemoteConnection's. 
        private static Hashtable _connections = new Hashtable();
 
        private SocketHandlerFactory _handlerFactory;

        // socket timeout data
        private static RegisteredWaitHandle _registeredWaitHandle; 
        private static WaitOrTimerCallback _socketTimeoutDelegate;
        private static AutoResetEvent _socketTimeoutWaitHandle; 
        private static TimeSpan _socketTimeoutPollTime = TimeSpan.FromSeconds(10); 
        private SocketCachePolicy _socketCachePolicy;
        private TimeSpan _socketTimeout; 
        private int _receiveTimeout = 0;


        static SocketCache() 
        {
            InitializeSocketTimeoutHandler(); 
        } 

        internal SocketCache(SocketHandlerFactory handlerFactory, SocketCachePolicy socketCachePolicy, 
                                                                        TimeSpan socketTimeout)
        {
            _handlerFactory = handlerFactory;
            _socketCachePolicy = socketCachePolicy; 
            _socketTimeout = socketTimeout;
        } // SocketCache 
 
        internal TimeSpan SocketTimeout { get { return _socketTimeout; } set { _socketTimeout = value;} }
        internal int ReceiveTimeout { get { return _receiveTimeout; } set { _receiveTimeout = value;} } 
        internal SocketCachePolicy CachePolicy { get { return _socketCachePolicy; } set { _socketCachePolicy = value;}}


        private static void InitializeSocketTimeoutHandler() 
        {
            _socketTimeoutDelegate = new WaitOrTimerCallback(TimeoutSockets); 
            _socketTimeoutWaitHandle = new AutoResetEvent(false); 
            _registeredWaitHandle =
                ThreadPool.UnsafeRegisterWaitForSingleObject( 
                    _socketTimeoutWaitHandle,
                    _socketTimeoutDelegate,
                    "TcpChannelSocketTimeout",
                    _socketTimeoutPollTime, 
                    true); // execute only once
        } // InitializeSocketTimeoutHandler 
 
        private static void TimeoutSockets(Object state, Boolean wasSignalled)
        { 
            DateTime currentTime = DateTime.UtcNow;

            lock (_connections)
            { 
                foreach (DictionaryEntry entry in _connections)
                { 
                    RemoteConnection connection = (RemoteConnection)entry.Value; 
                    connection.TimeoutSockets(currentTime);
                } 
            }

            _registeredWaitHandle.Unregister(null);
            _registeredWaitHandle = 
                ThreadPool.UnsafeRegisterWaitForSingleObject(
                    _socketTimeoutWaitHandle, 
                    _socketTimeoutDelegate, 
                    "TcpChannelSocketTimeout",
                    _socketTimeoutPollTime, 
                    true); // execute only once
        } // TimeoutSockets

 

        internal SocketHandler CreateSocketHandler(Socket socket, String machineAndPort) 
        { 
            socket.ReceiveTimeout = _receiveTimeout;
            return _handlerFactory(socket, this, machineAndPort); 
        }


        // The key is expected to of the form "machinename:port" 
        public SocketHandler GetSocket(String machinePortAndSid, bool openNew)
        { 
            RemoteConnection connection = (RemoteConnection)_connections[machinePortAndSid]; 
            if (openNew || connection == null)
            { 
                connection = new RemoteConnection(this, machinePortAndSid);

                // doesn't matter if different RemoteConnection's get written at
                //   the same time (GC will come along and close them). 
                lock (_connections)
                { 
                    _connections[machinePortAndSid] = connection; 
                }
            } 

            return connection.GetSocket();
        } // GetSocket
 
        public void ReleaseSocket(String machinePortAndSid, SocketHandler socket)
        { 
            RemoteConnection connection = (RemoteConnection)_connections[machinePortAndSid]; 
            if (connection != null)
            { 
                connection.ReleaseSocket(socket);
            }
            else
            { 
                // there should have been a connection, so let's just close
                //   this socket. 
                socket.Close(); 
            }
        } // ReleaseSocket 


    } // SocketCache
 

 
 
} // namespace System.Runtime.Remoting.Channels
 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
                        

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