feat(tcp): TCPStreamer DataSources, in-process TCPStreamService, stream multiplexing and TCPStreamJoin

Add TCPStreamer/TCPStreamerClient (TCP transport behind the UDPSServerI/UDPSClientI
seam), an optional single in-process TCPStreamService serving many streams over
worker threads, multiplexed SUBSCRIBE (comma list, stream index in fragmentIdx),
and TCPStreamJoin, which merges several streams into one sample-and-hold stream
paced by a master. StreamHub takes a comma list of streams over one connection.
Includes GTests, E2E scenarios s58-s73 and docs.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Source/Components/DataSources/TCPStreamer/TCPStreamer.h

@@ -0,0 +1,112 @@
+/**
+ * @file TCPStreamer.h
+ * @brief Header file for class TCPStreamer
+ * @date 05/11/2026
+ * @author Martino Ferrari
+ *
+ * @copyright Copyright 2015 F4E | European Joint Undertaking for ITER and
+ * the Development of Fusion Energy ('Fusion for Energy').
+ * Licensed under the EUPL, Version 1.1 or - as soon they will be approved
+ * by the European Commission - subsequent versions of the EUPL (the "Licence")
+ * You may not use this work except in compliance with the Licence.
+ * You may obtain a copy of the Licence at: http://ec.europa.eu/idabc/eupl
+ *
+ * @warning Unless required by applicable law or agreed to in writing,
+ * software distributed under the Licence is distributed on an "AS IS"
+ * basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+ * or implied. See the Licence permissions and limitations under the Licence.
+ *
+ * @details This header file contains the declaration of the class TCPStreamer
+ * with all of its public, protected and private members.
+ */
+
+#ifndef TCPSTREAMER_H_
+#define TCPSTREAMER_H_
+
+#include "TCPSServer.h"
+#include "TCPSServiceStream.h"
+#include "UDPStreamer.h"
+
+namespace MARTe {
+
+/**
+ * @brief A DataSource that streams MARTe2 signals to TCP clients.
+ *
+ * @details Identical to UDPStreamer (same signals, quantisation, time modes and
+ * PublishingMode handling, same UDPS wire format) except that the network side
+ * is a TCPSServer: every client gets the CONFIG on connect and then every DATA
+ * frame, in order, over its own TCP connection. A client that cannot keep up
+ * only loses its own frames (counted by GetClientDrops()) and is disconnected
+ * after ClientStallTimeout seconds without progress; the RT thread and the
+ * other clients are unaffected.
+ *
+ * @par Configuration
+ * All UDPStreamer keys apply except the UDP-only ones (MulticastGroup,
+ * Interface, DataPort, ClientTimeout), which are rejected.
+ * | Parameter          | Type   | Default | Description |
+ * |--------------------|--------|---------|-------------|
+ * | Port               | uint16 | 44500   | TCP listen port. |
+ * | MaxPayloadSize     | uint32 | 60000   | Frame budget used to size Accumulate batches. |
+ * | MaxClients         | uint32 | 16      | Simultaneous clients (1..1024). |
+ * | ClientQueueDepth   | uint32 | 8       | DATA frames queued per client (1..4096). |
+ * | ClientStallTimeout | uint32 | 5       | Seconds without progress before a client is dropped; 0 disables. |
+ * | SendBufferSize     | uint32 | 0       | SO_SNDBUF for client sockets; 0 keeps the OS default. |
+ *
+ * @par Shared service mode
+ * With `Service = <name of a TCPStreamService>` the DataSource does not open a
+ * socket of its own: it publishes a stream called `StreamName` (default: the
+ * DataSource name) through the shared in-process service, which serves many
+ * streams from one port with a pool of worker threads. Clients select the
+ * stream with the `StreamName` key of TCPStreamerClient / StreamHub. In this
+ * mode Port, MaxClients, ClientQueueDepth, ClientStallTimeout and
+ * SendBufferSize belong to the service and are rejected here.
+ * | Parameter  | Type   | Default         | Description |
+ * |------------|--------|-----------------|-------------|
+ * | Service    | string | *(absent)*      | Object name of the TCPStreamService. |
+ * | StreamName | string | DataSource name | Stream name, unique per service (1..255 chars). |
+ *
+ * @par Example
+ * <pre>
+ * +Streamer = {
+ *     Class = TCPStreamer
+ *     Port  = 44500
+ *     Signals = {
+ *         Time = { Type = uint64 }
+ *         Value = { Type = float32 }
+ *     }
+ * }
+ * </pre>
+ */
+class TCPStreamer : public UDPStreamer {
+public:
+    CLASS_REGISTER_DECLARATION()
+
+    TCPStreamer();
+    virtual ~TCPStreamer();
+
+    /** Rejects the UDP-only keys, then behaves as UDPStreamer::Initialise(). */
+    virtual bool Initialise(StructuredDataI &data);
+
+    /** @return true when publishing through a TCPStreamService. */
+    bool UsesService() const;
+    /** @return the port actually bound (meaningful once started; resolves Port = 0). */
+    uint16 GetBoundPort() const;
+    /** @return clients currently connected. */
+    uint32 GetClientCount() const;
+    /** @return DATA frames dropped across all clients because their queue was full. */
+    uint64 GetClientDrops() const;
+    /** @return clients disconnected for exceeding ClientStallTimeout. */
+    uint32 GetStallEvictions() const;
+
+protected:
+    virtual uint32 DefaultMaxPayloadSize() const;
+    virtual bool InitialiseTransport(StructuredDataI &data);
+
+private:
+    TCPSServer *tcpServer;            /**< Alias of the private transport (NULL in service mode). */
+    TCPSServiceStream *serviceStream; /**< Alias of the service handle (NULL in standalone mode). */
+};
+
+} /* namespace MARTe */
+
+#endif /* TCPSTREAMER_H_ */