demo: Add netty example code

This demonstrates using Netty 4.x with junixsocket.

Author: kohlschuetter

junixsocket-demo/pom.xml

@@ -90,6 +90,11 @@
             <artifactId>mina-core</artifactId>
             <version>2.2.3</version>
         </dependency>
+        <dependency>
+            <groupId>io.netty</groupId>
+            <artifactId>netty-all</artifactId>
+            <version>4.1.54.Final</version>
+        </dependency>
     </dependencies>
     <build>
         <plugins>

junixsocket-demo/src/main/java/module-info.java

@@ -16,6 +16,7 @@
   requires mina.core;
   requires static com.kohlschutter.annotations.compiletime;
   requires static org.eclipse.jdt.annotation;
+  requires io.netty.all;
 
   exports org.newsclub.net.unix.demo.rmi.services to java.rmi;
   exports org.newsclub.net.unix.demo.rmi.fd to java.rmi;

junixsocket-demo/src/main/java/org/newsclub/net/unix/demo/netty/EchoServer.java

@@ -0,0 +1,92 @@
+/*
+ * junixsocket
+ *
+ * Copyright 2009-2023 Christian Kohlschütter
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.newsclub.net.unix.demo.netty;
+
+import java.io.File;
+import java.nio.channels.spi.SelectorProvider;
+import java.util.concurrent.Executor;
+
+import org.newsclub.net.unix.AFSocketAddress;
+import org.newsclub.net.unix.AFUNIXSelectorProvider;
+import org.newsclub.net.unix.AFUNIXSocketAddress;
+
+import io.netty.bootstrap.ServerBootstrap;
+import io.netty.channel.ChannelFuture;
+import io.netty.channel.ChannelInitializer;
+import io.netty.channel.ChannelOption;
+import io.netty.channel.EventLoopGroup;
+import io.netty.channel.nio.NioEventLoopGroup;
+import io.netty.channel.socket.SocketChannel;
+import io.netty.channel.socket.nio.NioServerSocketChannel;
+
+/**
+ * Echos any incoming data.
+ * <p>
+ * Based on example code from <a href="https://netty.io/wiki/user-guide-for-4.x.html">Netty user
+ * guide for 4.x</a>
+ */
+public class EchoServer {
+  private final AFSocketAddress addr;
+
+  public EchoServer(AFSocketAddress addr) {
+    this.addr = addr;
+  }
+
+  public void run() throws Exception {
+    SelectorProvider provider = AFUNIXSelectorProvider.provider();
+    // SelectorProvider provider = AFTIPCSelectorProvider.provider();
+
+    // We need to specify our custom selector provider here (1), as well as in (3)
+    EventLoopGroup bossGroup = new NioEventLoopGroup(0, (Executor) null, provider); // (1)
+    EventLoopGroup workerGroup = new NioEventLoopGroup(0, (Executor) null, provider); // (1)
+    try {
+      ServerBootstrap b = new ServerBootstrap(); // (2)
+      b.group(bossGroup, workerGroup) //
+          .channelFactory(() -> new NioServerSocketChannel(provider)) // (3)
+          .childHandler(new ChannelInitializer<SocketChannel>() { // (4)
+            @Override
+            public void initChannel(SocketChannel ch) throws Exception {
+              ch.pipeline().addLast(new EchoServerHandler());
+            }
+          }) //
+          .option(ChannelOption.SO_BACKLOG, 128) // (5)
+          .childOption(ChannelOption.SO_KEEPALIVE, true); // (6)
+
+      // Bind and start to accept incoming connections.
+      ChannelFuture f = b.bind(addr).sync(); // (7)
+
+      // Wait until the server socket is closed.
+      // In this example, this does not happen, but you can do that to gracefully
+      // shut down your server.
+      f.channel().closeFuture().sync();
+    } finally {
+      workerGroup.shutdownGracefully();
+      bossGroup.shutdownGracefully();
+    }
+  }
+
+  public static void main(String[] args) throws Exception {
+    File path = new File("/tmp/nettyecho");
+    if (args.length > 0) {
+      path = new File(args[0]);
+    }
+
+    new EchoServer(AFUNIXSocketAddress.of(path)).run();
+    // new EchoServer(AFTIPCSocketAddress.ofService(Scope.SCOPE_CLUSTER, 128, 3)).run();
+  }
+}

junixsocket-demo/src/main/java/org/newsclub/net/unix/demo/netty/EchoServerHandler.java

@@ -0,0 +1,43 @@
+/*
+ * junixsocket
+ *
+ * Copyright 2009-2023 Christian Kohlschütter
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.newsclub.net.unix.demo.netty;
+
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.channel.ChannelInboundHandlerAdapter;
+
+/**
+ * Handles a server-side channel.
+ * <p>
+ * Based on example code from <a href="https://netty.io/wiki/user-guide-for-4.x.html">Netty user
+ * guide for 4.x</a>
+ */
+class EchoServerHandler extends ChannelInboundHandlerAdapter { // (1)
+
+  @Override
+  public void channelRead(ChannelHandlerContext ctx, Object msg) {
+    ctx.write(msg); // (1)
+    ctx.flush(); // (2)
+  }
+
+  @Override
+  public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) { // (4)
+    // Close the connection when an exception is raised.
+    cause.printStackTrace();
+    ctx.close();
+  }
+}