Make Network Socket in UdpPubSubConnection reachable (#3385)

* Initial plan

* Add public properties to expose UDP client sockets in UdpPubSubConnection

Co-authored-by: romanett <[email protected]>

* Update documentation comments to be more accurate

Co-authored-by: romanett <[email protected]>

* Optimize property access by returning list directly instead of creating wrapper

Co-authored-by: romanett <[email protected]>

* Use AsReadOnly() to ensure true immutability and prevent external modification

Co-authored-by: romanett <[email protected]>

* Remove unused import

Co-authored-by: romanett <[email protected]>

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: romanett <[email protected]>

Author: Copilot

Libraries/Opc.Ua.PubSub/Transport/UdpPubSubConnection.cs

@@ -95,6 +95,38 @@ public UdpPubSubConnection(
         /// </summary>
         public int Port { get; }
 
+        /// <summary>
+        /// Gets the list of publisher UDP clients.
+        /// Returns a read-only list of active UDP clients used for publishing.
+        /// Can be used to configure socket settings such as ReceiveBuffer size.
+        /// </summary>
+        public IReadOnlyList<UdpClient> PublisherUdpClients
+        {
+            get
+            {
+                lock (Lock)
+                {
+                    return m_publisherUdpClients.AsReadOnly();
+                }
+            }
+        }
+
+        /// <summary>
+        /// Gets the list of subscriber UDP clients.
+        /// Returns a read-only list of active UDP clients used for subscribing.
+        /// Can be used to configure socket settings such as ReceiveBuffer size.
+        /// </summary>
+        public IReadOnlyList<UdpClient> SubscriberUdpClients
+        {
+            get
+            {
+                lock (Lock)
+                {
+                    return m_subscriberUdpClients.AsReadOnly();
+                }
+            }
+        }
+
         /// <summary>
         /// Perform specific Start tasks
         /// </summary>

Tests/Opc.Ua.PubSub.Tests/Transport/UdpPubSubConnectionTests.cs

@@ -523,5 +523,95 @@ private static IPAddress GetFirstActiveNic()
 
             return null;
         }
+
+        [Test(Description = "Validate UDP client socket access before connection is started")]
+        public void ValidateUdpPubSubConnectionSocketAccessBeforeStart()
+        {
+            // Arrange
+            Assert.IsNotNull(
+                m_udpPublisherConnection,
+                "The UADP connection from standard configuration is invalid.");
+
+            // Act - Access clients before connection is started
+            IReadOnlyList<UdpClient> publisherClients = m_udpPublisherConnection.PublisherUdpClients;
+            IReadOnlyList<UdpClient> subscriberClients = m_udpPublisherConnection.SubscriberUdpClients;
+
+            // Assert - Should return empty lists before connection is started
+            Assert.IsNotNull(publisherClients, "PublisherUdpClients should not be null");
+            Assert.IsNotNull(subscriberClients, "SubscriberUdpClients should not be null");
+            Assert.AreEqual(0, publisherClients.Count, "PublisherUdpClients should be empty before start");
+            Assert.AreEqual(0, subscriberClients.Count, "SubscriberUdpClients should be empty before start");
+        }
+
+        [Test(Description = "Validate UDP client socket access after connection is started")]
+        public void ValidateUdpPubSubConnectionSocketAccessAfterStart()
+        {
+            // Arrange
+            Assert.IsNotNull(
+                m_udpPublisherConnection,
+                "The UADP connection from standard configuration is invalid.");
+
+            // Act - Start the connection
+            m_udpPublisherConnection.Start();
+
+            try
+            {
+                // Access clients after connection is started
+                IReadOnlyList<UdpClient> publisherClients = m_udpPublisherConnection.PublisherUdpClients;
+                IReadOnlyList<UdpClient> subscriberClients = m_udpPublisherConnection.SubscriberUdpClients;
+
+                // Assert - Should have clients after connection is started
+                Assert.IsNotNull(publisherClients, "PublisherUdpClients should not be null");
+                Assert.IsNotNull(subscriberClients, "SubscriberUdpClients should not be null");
+
+                // Publisher should have clients since there are publishers configured
+                if (m_udpPublisherConnection.Publishers.Count > 0)
+                {
+                    Assert.Greater(publisherClients.Count, 0, "PublisherUdpClients should not be empty when publishers exist");
+
+                    // Verify we can access the underlying socket
+                    foreach (UdpClient client in publisherClients)
+                    {
+                        Assert.IsNotNull(client, "UDP client should not be null");
+                        Assert.IsNotNull(client.Client, "UDP client Socket should not be null");
+
+                        // Verify we can read socket properties (e.g., ReceiveBufferSize)
+                        int receiveBufferSize = client.Client.ReceiveBufferSize;
+                        Assert.Greater(receiveBufferSize, 0, "ReceiveBufferSize should be greater than 0");
+
+                        m_logger.LogInformation(
+                            "Publisher UDP Socket - ReceiveBufferSize: {Size}, LocalEndPoint: {Endpoint}",
+                            receiveBufferSize,
+                            client.Client.LocalEndPoint);
+                    }
+                }
+            }
+            finally
+            {
+                // Cleanup - Stop the connection
+                m_udpPublisherConnection.Stop();
+            }
+        }
+
+        [Test(Description = "Validate that UDP client list is read-only")]
+        public void ValidateUdpPubSubConnectionSocketListIsReadOnly()
+        {
+            // Arrange
+            Assert.IsNotNull(
+                m_udpPublisherConnection,
+                "The UADP connection from standard configuration is invalid.");
+
+            // Act
+            IReadOnlyList<UdpClient> publisherClients = m_udpPublisherConnection.PublisherUdpClients;
+            IReadOnlyList<UdpClient> subscriberClients = m_udpPublisherConnection.SubscriberUdpClients;
+
+            // Assert - The returned collections should be read-only
+            Assert.IsNotNull(publisherClients, "PublisherUdpClients should not be null");
+            Assert.IsNotNull(subscriberClients, "SubscriberUdpClients should not be null");
+
+            // Verify that the collections are truly read-only (no Add/Remove methods exposed)
+            Assert.IsInstanceOf<IReadOnlyList<UdpClient>>(publisherClients, "PublisherUdpClients should be IReadOnlyList");
+            Assert.IsInstanceOf<IReadOnlyList<UdpClient>>(subscriberClients, "SubscriberUdpClients should be IReadOnlyList");
+        }
     }
 }