Solution

src/main/java/koz01/java2/lab08/IndexReader.java

@@ -35,6 +35,18 @@ public class IndexReader {
 
 	}
 
+	public byte[] readData(int index) {
+
+		try (FileChannel fc = FileChannel.open(getFile())) {
+			return getData(fc, index);
+		}
+		catch (IOException exc) {
+			log.error("read", exc);
+			return null;
+		}
+
+	}
+
 	private Path getFile() throws IOException {
 		Path LocalFile = Files.createTempFile(null, null).getParent().resolve(
 			IMAGE_NAME);
@@ -56,6 +68,25 @@ public class IndexReader {
 	}
 
 	private byte[] getData(FileChannel fc, int index) throws IOException {
-		return new byte[0];
+		//position := readInt(index*8 + 4)
+		//length := readInt(index*8 + 8)
+		
+		//data := readData(position, length)
+		//return data;
+		
+		//go to specific position ... FileChannel.position(long)
+		//read data ... FileChannel.read(ByteBuffer)
+		//ByteBuffer.getInt()
+		
+		ByteBuffer bb = ByteBuffer.allocate(8);
+		fc.position(index*8 + 4);
+		fc.read(bb);
+		bb.flip();
+		int positon = bb.getInt();
+		int legth = bb.getInt();
+		bb = ByteBuffer.allocate(legth);
+		fc.position(positon);
+		fc.read(bb);
+		return bb.array();
 	}
 }

src/main/java/koz01/java2/lab08/RemoteImageServer.java

+package koz01.java2.lab08;
+
+import java.io.IOException;
+import java.net.InetSocketAddress;
+import java.nio.ByteBuffer;
+import java.nio.channels.ByteChannel;
+import java.nio.channels.SelectionKey;
+import java.nio.channels.Selector;
+import java.nio.channels.ServerSocketChannel;
+import java.nio.channels.SocketChannel;
+import java.util.Iterator;
+
+import lombok.extern.log4j.Log4j2;
+
+@Log4j2
+public class RemoteImageServer {
+
+	public static void main(String[] args) throws IOException {
+		IndexReader indexReader = new IndexReader();
+		int port = Integer.parseInt(args[0]);
+		ServerSocketChannel ssc = ServerSocketChannel.open();
+		ssc.bind(new InetSocketAddress(port));
+		log.info("Waiting connection on port {}", port);
+		ssc.configureBlocking(false);
+		Selector selector = Selector.open();
+		ssc.register(selector, SelectionKey.OP_ACCEPT);
+		while (true) {
+			selector.select();
+			Iterator<SelectionKey> keys = selector.selectedKeys().iterator();
+			while (keys.hasNext()) {
+				SelectionKey sk = keys.next();
+				if (sk.channel() == ssc) {
+					SocketChannel sc = ssc.accept();
+					sc.configureBlocking(false);
+					log.info("Connected: {}", sc.getRemoteAddress());
+					sc.register(selector, SelectionKey.OP_READ | SelectionKey.OP_CONNECT);
+					// register sc in selector for Read Operation
+				}
+				else {
+					// get SocketChannel from selection key
+					// readInt from socketChannel
+					// writeInt to socketChannel ... length of image
+					// writeData to socketChannel
+					ByteChannel sc = (ByteChannel) sk.channel();
+					ByteBuffer bb = ByteBuffer.allocate(4);
+					if (sc.read(bb) < 0) {
+						// connection is closed so remove selector
+						sk.cancel();
+					}
+					bb.flip();
+					int index = bb.getInt();
+					byte[] data = indexReader.readData(index);
+					bb.clear();
+					bb.putInt(data.length);
+					bb.flip();
+					sc.write(bb);
+					bb = ByteBuffer.wrap(data);
+					bb.position(bb.limit());
+					bb.flip();
+					sc.write(bb);
+				}
+				keys.remove();
+			}
+		}
+	}
+
+}

src/main/resources/koz01/java2/lab08/RemoteLoader.fxml

@@ -13,8 +13,8 @@
       <Label layoutX="81.0" layoutY="592.0" prefHeight="26.0" prefWidth="103.0" text="Index obrázku" />
       <Button fx:id="load" disable="true" layoutX="306.0" layoutY="592.0" mnemonicParsing="false" onAction="#readButton" text="Načti" />
       <Label layoutX="81.0" layoutY="531.0" text="Adresa" />
-      <TextField fx:id="adress" layoutX="149.0" layoutY="526.0" prefHeight="26.0" prefWidth="131.0" />
-      <TextField fx:id="port" layoutX="207.0" layoutY="560.0" prefHeight="26.0" prefWidth="73.0" />
+      <TextField fx:id="adress" layoutX="149.0" layoutY="526.0" prefHeight="26.0" prefWidth="131.0" text="127.0.0.1" />
+      <TextField fx:id="port" layoutX="207.0" layoutY="560.0" prefHeight="26.0" prefWidth="73.0" text="10000" />
       <Label layoutX="81.0" layoutY="565.0" prefHeight="16.0" prefWidth="46.0" text="Port" />
       <Button fx:id="connect" layoutX="306.0" layoutY="526.0" mnemonicParsing="false" onAction="#connect" text="Připojit" />
    </children>