Enable client support for multiple sessions on a single channel (#1659)

* Client API changes to support multiple sessions on a single channel
* Tested against freeopcua:python:server and ProSys simulation server

Libraries/Opc.Ua.Client/Session.cs

@@ -799,28 +799,41 @@ namespace Opc.Ua.Client
         }
 
         /// <summary>
-        /// Creates a new communication session with a server using a reverse connection.
+        /// Creates a new session with a server using the specified channel by invoking the CreateSession service
         /// </summary>
         /// <param name="configuration">The configuration for the client application.</param>
-        /// <param name="connection">The client endpoint for the reverse connect.</param>
+        /// <param name="channel">The channel for the server.</param>
         /// <param name="endpoint">The endpoint for the server.</param>
-        /// <param name="updateBeforeConnect">If set to <c>true</c> the discovery endpoint is used to update the endpoint description before connecting.</param>
-        /// <param name="checkDomain">If set to <c>true</c> then the domain in the certificate must match the endpoint used.</param>
-        /// <param name="sessionName">The name to assign to the session.</param>
-        /// <param name="sessionTimeout">The timeout period for the session.</param>
-        /// <param name="identity">The user identity to associate with the session.</param>
-        /// <param name="preferredLocales">The preferred locales.</param>
-        /// <returns>The new session object.</returns>
-        public static async Task<Session> Create(
+        /// <param name="clientCertificate">The certificate to use for the client.</param>
+        /// <param name="availableEndpoints">The list of available endpoints returned by server in GetEndpoints() response.</param>
+        /// <param name="discoveryProfileUris">The value of profileUris used in GetEndpoints() request.</param>
+        /// <returns></returns>
+        public static Session Create(
+           ApplicationConfiguration configuration,
+           ITransportChannel channel,
+           ConfiguredEndpoint endpoint,
+           X509Certificate2 clientCertificate,
+           EndpointDescriptionCollection availableEndpoints = null,
+           StringCollection discoveryProfileUris = null)
+        {
+            return new Session(channel, configuration, endpoint, clientCertificate, availableEndpoints, discoveryProfileUris);
+        }
+
+        /// <summary>
+        /// Creates a secure channel to the specified endpoint.
+        /// </summary>
+        /// <param name="configuration">The application configuration.</param>
+        /// <param name="connection">The client endpoint for the reverse connect.</param>
+        /// <param name="endpoint">A configured endpoint to connect to.</param> 
+        /// <param name="updateBeforeConnect">Update configuration based on server prior connect.</param>
+        /// <param name="checkDomain">Check that the certificate specifies a valid domain (computer) name.</param>
+        /// <returns>A <see cref="Task"/> representing the asynchronous operation.</returns>
+        public static async Task<ITransportChannel> CreateChannelAsync(
             ApplicationConfiguration configuration,
             ITransportWaitingConnection connection,
             ConfiguredEndpoint endpoint,
             bool updateBeforeConnect,
-            bool checkDomain,
-            string sessionName,
-            uint sessionTimeout,
-            IUserIdentity identity,
-            IList<string> preferredLocales)
+            bool checkDomain)
         {
             endpoint.UpdateBeforeConnect = updateBeforeConnect;
 
@@ -888,6 +901,36 @@ namespace Opc.Ua.Client
                      messageContext);
             }
 
+            return channel;
+        }
+
+        /// <summary>
+        /// Creates a new communication session with a server using a reverse connection.
+        /// </summary>
+        /// <param name="configuration">The configuration for the client application.</param>
+        /// <param name="connection">The client endpoint for the reverse connect.</param>
+        /// <param name="endpoint">The endpoint for the server.</param>
+        /// <param name="updateBeforeConnect">If set to <c>true</c> the discovery endpoint is used to update the endpoint description before connecting.</param>
+        /// <param name="checkDomain">If set to <c>true</c> then the domain in the certificate must match the endpoint used.</param>
+        /// <param name="sessionName">The name to assign to the session.</param>
+        /// <param name="sessionTimeout">The timeout period for the session.</param>
+        /// <param name="identity">The user identity to associate with the session.</param>
+        /// <param name="preferredLocales">The preferred locales.</param>
+        /// <returns>The new session object.</returns>
+        public static async Task<Session> Create(
+            ApplicationConfiguration configuration,
+            ITransportWaitingConnection connection,
+            ConfiguredEndpoint endpoint,
+            bool updateBeforeConnect,
+            bool checkDomain,
+            string sessionName,
+            uint sessionTimeout,
+            IUserIdentity identity,
+            IList<string> preferredLocales)
+        {
+            // initialize the channel which will be created with the server.
+            ITransportChannel channel = await Session.CreateChannelAsync(configuration, connection, endpoint, updateBeforeConnect, checkDomain).ConfigureAwait(false);
+
             // create the session object.
             Session session = new Session(channel, configuration, endpoint, null);
 
@@ -1074,6 +1117,45 @@ namespace Opc.Ua.Client
 
             return session;
         }
+
+        /// <summary>
+        /// Recreates a session based on a specified template using the provided channel.
+        /// </summary>
+        /// <param name="template">The Session object to use as template</param>
+        /// <param name="transportChannel">The waiting reverse connection.</param>
+        /// <returns>The new session object.</returns>
+        public static Session Recreate(Session template, ITransportChannel transportChannel)
+        {
+            var messageContext = template.m_configuration.CreateMessageContext();
+            messageContext.Factory = template.Factory;
+
+            // create the session object.
+            Session session = new Session(transportChannel, template, true);
+
+            try
+            {
+                // open the session.
+                session.Open(
+                    template.m_sessionName,
+                    (uint)template.m_sessionTimeout,
+                    template.m_identity,
+                    template.m_preferredLocales,
+                    template.m_checkDomain);
+
+                // create the subscriptions.
+                foreach (Subscription subscription in session.Subscriptions)
+                {
+                    subscription.Create();
+                }
+            }
+            catch (Exception e)
+            {
+                session.Dispose();
+                throw ServiceResultException.Create(StatusCodes.BadCommunicationError, e, "Could not recreate session. {0}", template.m_sessionName);
+            }
+
+            return session;
+        }
         #endregion
 
         #region Delegates and Events
@@ -1100,13 +1182,13 @@ namespace Opc.Ua.Client
         /// </summary>
         public void Reconnect()
         {
-            Reconnect(null);
+            Reconnect(null, null);
         }
 
         /// <summary>
         /// Reconnects to the server after a network failure using a waiting connection.
         /// </summary>
-        public void Reconnect(ITransportWaitingConnection connection)
+        public void Reconnect(ITransportWaitingConnection connection, ITransportChannel transportChannel = null)
         {
             try
             {
@@ -1204,6 +1286,10 @@ namespace Opc.Ua.Client
                         TransportChannel = channel;
                     }
                 }
+                else if (transportChannel != null)
+                {
+                    TransportChannel = transportChannel;
+                }
                 else
                 {
                     // check if the channel supports reconnect.
@@ -3206,13 +3292,23 @@ namespace Opc.Ua.Client
         /// </summary>
         public override StatusCode Close()
         {
-            return Close(m_keepAliveInterval);
+            return Close(m_keepAliveInterval, true);
+        }
+
+        /// <summary>
+        /// Close the session with the server and optionally closes the channel.
+        /// </summary>
+        /// <param name="closeChannel"></param>
+        /// <returns></returns>
+        public StatusCode Close(bool closeChannel)
+        {
+            return Close(m_keepAliveInterval, closeChannel);
         }
 
         /// <summary>
         /// Disconnects from the server and frees any network resources with the specified timeout.
         /// </summary>
-        public virtual StatusCode Close(int timeout)
+        public virtual StatusCode Close(int timeout, bool closeChannel = true)
         {
             // check if already called.
             if (Disposed)
@@ -3255,7 +3351,10 @@ namespace Opc.Ua.Client
                     CloseSession(null, m_deleteSubscriptionsOnClose);
                     this.OperationTimeout = existingTimeout;
 
-                    CloseChannel();
+                    if (closeChannel)
+                    {
+                        CloseChannel();
+                    }
 
                     // raised notification indicating the session is closed.
                     SessionCreated(null, null);
@@ -3278,7 +3377,11 @@ namespace Opc.Ua.Client
             }
 
             // clean up.
-            Dispose();
+            if (closeChannel)
+            {
+                Dispose();
+            }
+
             return result;
         }
         #endregion
@@ -3469,7 +3572,6 @@ namespace Opc.Ua.Client
                     Utils.LogInfo("No subscriptions. Transfersubscription skipped.");
                 }
 
-                
             }
 
             return true;

Stack/Opc.Ua.Core/Stack/Client/ClientBase.cs

@@ -30,15 +30,7 @@ namespace Opc.Ua
         {
             if (channel == null) throw new ArgumentNullException(nameof(channel));
 
-            m_channel = channel;
-            m_useTransportChannel = true;
-
-            UaChannelBase uaChannel = channel as UaChannelBase;
-
-            if (uaChannel != null)
-            {
-                m_useTransportChannel = uaChannel.m_uaBypassChannel != null || uaChannel.UseBinaryEncoding;
-            }
+            InitializeChannel(channel);
         }
         #endregion
 
@@ -245,6 +237,23 @@ namespace Opc.Ua
         #endregion
 
         #region Public Methods
+        /// <summary>
+        /// Attach the channel to an already created client.
+        /// </summary>
+        /// <param name="channel">Channel to be used by the client</param>
+        public void AttachChannel(ITransportChannel channel)
+        {
+            InitializeChannel(channel);
+        }
+
+        /// <summary>
+        /// Detach the channel.
+        /// </summary>
+        public void DetachChannel()
+        {
+            m_channel = null;
+        }
+
         /// <summary>
         /// Closes the channel.
         /// </summary>
@@ -282,6 +291,23 @@ namespace Opc.Ua
         #endregion
 
         #region Protected Methods
+        /// <summary>
+        /// Initializes the channel.
+        /// </summary>
+        /// <param name="channel"></param>
+        protected void InitializeChannel(ITransportChannel channel)
+        {
+            m_channel = channel;
+            m_useTransportChannel = true;
+
+            UaChannelBase uaChannel = channel as UaChannelBase;
+
+            if (uaChannel != null)
+            {
+                m_useTransportChannel = uaChannel.m_uaBypassChannel != null || uaChannel.UseBinaryEncoding;
+            }
+        }
+
         /// <summary>
         /// Closes the channel.
         /// </summary>

Tests/Opc.Ua.Client.Tests/ClientFixture.cs

@@ -207,6 +207,27 @@ namespace Opc.Ua.Client.Tests
             return session;
         }
 
+        /// <summary>
+        /// Create a channel using the specified endpoint.
+        /// </summary>
+        /// <param name="endpoint">The configured endpoint</param>
+        /// <returns></returns>
+        public async Task<ITransportChannel> CreateChannelAsync(ConfiguredEndpoint endpoint)
+        {
+            return await Session.CreateChannelAsync(Config, null, endpoint, true, false).ConfigureAwait(false);
+        }
+
+        /// <summary>
+        /// Create a session using the specified channel.
+        /// </summary>
+        /// <param name="channel">The channel to use</param>
+        /// <param name="endpoint">The configured endpoint</param>
+        /// <returns></returns>
+        public Session CreateSession(ITransportChannel channel, ConfiguredEndpoint endpoint)
+        {
+            return Session.Create(Config, channel, endpoint, null);
+        }
+
         /// <summary>
         /// Get configured endpoint from url with security profile.
         /// </summary>

Tests/Opc.Ua.Client.Tests/ClientTest.cs

@@ -242,6 +242,34 @@ namespace Opc.Ua.Client.Tests
             session.Dispose();
         }
 
+        [Test, Order(240)]
+        public async Task ConnectMultipleSessionsAsync()
+        {
+            var endpoint = await ClientFixture.GetEndpointAsync(this.ServerUrl, SecurityPolicies.Basic256Sha256, this.Endpoints);
+            Assert.NotNull(endpoint);
+
+            var channel = await ClientFixture.CreateChannelAsync(endpoint).ConfigureAwait(false);
+            Assert.NotNull(channel);
+
+            var session1 = ClientFixture.CreateSession(channel, endpoint);
+            session1.Open("Session1", null);
+
+            var session2 = ClientFixture.CreateSession(channel, endpoint);
+            session2.Open("Session2", null);
+
+            session1.Close(closeChannel: false);
+            session1.DetachChannel();
+            session1.Dispose();
+
+            _ = session2.ReadValue(VariableIds.Server_ServerStatus, typeof(ServerStatusDataType));
+
+            session2.Close(closeChannel: false);
+            session2.DetachChannel();
+            session2.Dispose();
+
+            channel.Dispose();
+        }
+
         [Test, Order(300)]
         public new void GetOperationLimits()
         {