Merge pull request #10629 from SmartyAnsh/BAEL-4786_NIO_DatagramChannel

BAEL-4786 - DatagramChannel

core-java-modules/core-java-nio-2/src/main/java/com/baeldung/datagramchannel/DatagramChannelBuilder.java

@@ -0,0 +1,18 @@
+package com.baeldung.datagramchannel;
+
+import java.io.IOException;
+import java.net.SocketAddress;
+import java.nio.channels.DatagramChannel;
+
+public class DatagramChannelBuilder {
+    
+    public static DatagramChannel openChannel() throws IOException {
+        DatagramChannel datagramChannel = DatagramChannel.open();
+        return datagramChannel;
+    }
+    
+    public static DatagramChannel bindChannel(SocketAddress local) throws IOException {
+        return openChannel().bind(local); 
+    }
+
+}

core-java-modules/core-java-nio-2/src/main/java/com/baeldung/datagramchannel/DatagramClient.java

@@ -0,0 +1,31 @@
+package com.baeldung.datagramchannel;
+
+import java.io.IOException;
+import java.net.InetSocketAddress;
+import java.net.SocketAddress;
+import java.nio.ByteBuffer;
+import java.nio.channels.DatagramChannel;
+
+public class DatagramClient {
+    
+    public static DatagramChannel startClient() throws IOException {
+        DatagramChannel client = DatagramChannelBuilder.bindChannel(null);
+        client.configureBlocking(false);
+        return client;
+    }
+    
+    public static void sendMessage(DatagramChannel client, String msg, SocketAddress serverAddress) throws IOException {
+        ByteBuffer buffer = ByteBuffer.wrap(msg.getBytes());
+        client.send(buffer, serverAddress);
+    }
+
+    public static void main(String[] args) throws IOException {
+        DatagramChannel client = startClient();
+        String msg = "Hello, this is a Baeldung's DatagramChannel based UDP client!";
+        InetSocketAddress serverAddress = new InetSocketAddress("localhost", 7001);
+        
+        sendMessage(client, msg, serverAddress);
+        
+    }
+
+}

core-java-modules/core-java-nio-2/src/main/java/com/baeldung/datagramchannel/DatagramServer.java

@@ -0,0 +1,46 @@
+package com.baeldung.datagramchannel;
+
+import java.io.IOException;
+import java.net.InetSocketAddress;
+import java.net.SocketAddress;
+import java.nio.ByteBuffer;
+import java.nio.channels.DatagramChannel;
+
+public class DatagramServer {
+    
+    public static DatagramChannel startServer() throws IOException {
+        InetSocketAddress address = new InetSocketAddress("localhost", 7001);
+        DatagramChannel server = DatagramChannelBuilder.bindChannel(address);
+        
+        System.out.println("Server started at #" + address);
+        
+        return server;
+    }
+    
+    public static String receiveMessage(DatagramChannel server) throws IOException {
+        ByteBuffer buffer = ByteBuffer.allocate(1024);
+        SocketAddress remoteAdd = server.receive(buffer);
+        String message = extractMessage(buffer);
+        
+        System.out.println("Client at #" + remoteAdd + "  sent: " + message);
+        
+        return message;
+    }
+    
+    private static String extractMessage(ByteBuffer buffer) {
+        buffer.flip();
+
+        byte[] bytes = new byte[buffer.remaining()];
+        buffer.get(bytes);
+        
+        String msg = new String(bytes);
+        
+        return msg;
+    }
+
+    public static void main(String[] args) throws IOException {
+        DatagramChannel server = startServer();
+        receiveMessage(server);
+    }
+
+}

core-java-modules/core-java-nio-2/src/test/java/com/baeldung/datagramchannel/DatagramChannelUnitTest.java

@@ -0,0 +1,29 @@
+package com.baeldung.datagramchannel;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.io.IOException;
+import java.net.InetSocketAddress;
+import java.nio.channels.DatagramChannel;
+import org.junit.jupiter.api.Test;
+
+public class DatagramChannelUnitTest {
+    
+    @Test
+    public void whenClientSendsAndServerReceivesUDPPacket_thenCorrect() throws IOException {
+        DatagramChannel server = DatagramServer.startServer();
+        DatagramChannel client = DatagramClient.startClient();
+        
+        String msg1 = "Hello, this is a Baeldung's DatagramChannel based UDP client!";
+        String msg2 = "Hi again!, Are you there!";
+        
+        InetSocketAddress serverAddress = new InetSocketAddress("localhost", 7001);
+        
+        DatagramClient.sendMessage(client, msg1, serverAddress);
+        DatagramClient.sendMessage(client, msg2, serverAddress);
+        
+        assertEquals("Hello, this is a Baeldung's DatagramChannel based UDP client!", DatagramServer.receiveMessage(server));
+        assertEquals("Hi again!, Are you there!", DatagramServer.receiveMessage(server));
+    }
+
+}