Network tuner support - rtl_tcp (#2471)

* Add network tuner dialog

* wip: network tuner configs

* wip stash

* working tcp solution

* fix copyright headers

* fix: resolve rebase conflicts from jRTL library changeover

- Drop redundant JFrequencyControl digit-sizing fix now that upstream
  fixes the same issue via setColumns(1)
- Mark SUPPORTED_NETWORK_TUNERS final to match the new EnumSet style
- Replace removed SampleRate.getClosest() with a local nearest-match
  helper in NetworkTunerEditor

* Add mise config

src/test/java/io/github/dsheirer/source/tuner/network/NetworkTunerControllerTest.java

@@ -0,0 +1,95 @@
+/*
+ * *****************************************************************************
+ * Copyright (C) 2026 Jared Szechy
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ * ****************************************************************************
+ */
+
+package io.github.dsheirer.source.tuner.network;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.ByteBuffer;
+import io.github.dsheirer.source.tuner.ITunerErrorListener;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+/**
+ * Unit tests for the rtl_tcp wire protocol helpers in {@link NetworkTunerController}: command
+ * encoding and handshake header validation.
+ */
+public class NetworkTunerControllerTest {
+    @Test
+    public void testEncodeCommandProducesFiveByteBigEndianPacket() {
+        //Command 0x01 (set frequency) with parameter 100_000_000 (100 MHz)
+        byte[] expected = ByteBuffer.allocate(5).put((byte) 0x01).putInt(100_000_000).array();
+        byte[] actual = NetworkTunerController.encodeCommand(0x01, 100_000_000);
+        assertEquals(5, actual.length);
+        assertArrayEquals(expected, actual);
+    }
+
+    @Test
+    public void testEncodeCommandNegativeParameterEncodesAsUnsignedBigEndian() {
+        //rtl_tcp treats the 4-byte parameter as an unsigned 32-bit value - verify negative Java
+        //ints (used to represent values > Integer.MAX_VALUE) round-trip through the same bytes
+        //as ByteBuffer.putInt() would produce.
+        byte[] expected = ByteBuffer.allocate(5).put((byte) 0x02).putInt(-1).array();
+        byte[] actual = NetworkTunerController.encodeCommand(0x02, -1);
+        assertArrayEquals(expected, actual);
+    }
+
+    @Test
+    public void testReadAndValidateHandshakeAcceptsValidMagic() throws IOException {
+        byte[] header = new byte[]{'R', 'T', 'L', '0', 0, 0, 0, 0, 0, 0, 0, 1};
+        NetworkTunerController controller = createController();
+        //Should not throw
+        controller.readAndValidateHandshake(new ByteArrayInputStream(header));
+    }
+
+    @Test
+    public void testReadAndValidateHandshakeRejectsInvalidMagic() {
+        byte[] header = new byte[]{'X', 'X', 'X', 'X', 0, 0, 0, 0, 0, 0, 0, 1};
+        NetworkTunerController controller = createController();
+        InputStream in = new ByteArrayInputStream(header);
+        assertThrows(IOException.class, () -> controller.readAndValidateHandshake(in));
+    }
+
+    @Test
+    public void testReadAndValidateHandshakeRejectsTruncatedHeader() {
+        byte[] header = new byte[]{'R', 'T', 'L', '0'};
+        NetworkTunerController controller = createController();
+        InputStream in = new ByteArrayInputStream(header);
+        assertThrows(IOException.class, () -> controller.readAndValidateHandshake(in));
+    }
+
+    private static NetworkTunerController createController() {
+        NetworkTunerConfiguration config = NetworkTunerConfiguration.create();
+        config.setHost("localhost");
+        config.setPort((short) 1234);
+        return new NetworkTunerController(new ITunerErrorListener() {
+            @Override
+            public void setErrorMessage(String errorMessage) {
+            }
+
+            @Override
+            public void tunerRemoved() {
+            }
+        }, config);
+    }
+}