Echo ping-pong server with detecting simplest quit command.

2024/07/netty_pingpong_demo1/netty_pingpong_demo1/.gitignore

@@ -0,0 +1,42 @@
+.gradle
+build/
+!gradle/wrapper/gradle-wrapper.jar
+!**/src/main/**/build/
+!**/src/test/**/build/
+
+### IntelliJ IDEA ###
+.idea/modules.xml
+.idea/jarRepositories.xml
+.idea/compiler.xml
+.idea/libraries/
+*.iws
+*.iml
+*.ipr
+out/
+!**/src/main/**/out/
+!**/src/test/**/out/
+
+### Eclipse ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+bin/
+!**/src/main/**/bin/
+!**/src/test/**/bin/
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+
+### VS Code ###
+.vscode/
+
+### Mac OS ###
+.DS_Store

2024/07/netty_pingpong_demo1/netty_pingpong_demo1/build.gradle.kts

@@ -0,0 +1,27 @@
+plugins {
+    id("java")
+}
+
+group = "ch.polgrabia.demos"
+version = "1.0-SNAPSHOT"
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+    implementation("ch.qos.logback:logback-classic:1.5.6")
+    implementation(group = "io.netty", name = "netty-all", version = "4.1.112.Final")
+    testImplementation(platform("org.junit:junit-bom:5.10.0"))
+    testImplementation("org.junit.jupiter:junit-jupiter")
+}
+
+tasks.test {
+    useJUnitPlatform()
+}
+
+java {
+    toolchain {
+        languageVersion.set(JavaLanguageVersion.of(17))
+    }
+}

2024/07/netty_pingpong_demo1/netty_pingpong_demo1/gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,6 @@
+#Wed Jul 31 18:47:08 CEST 2024
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.5-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

2024/07/netty_pingpong_demo1/netty_pingpong_demo1/gradlew

@@ -0,0 +1,234 @@
+#!/bin/sh
+
+#
+# Copyright © 2015-2021 the original authors.
+#
+# 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
+#
+#      https://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.
+#
+
+##############################################################################
+#
+#   Gradle start up script for POSIX generated by Gradle.
+#
+#   Important for running:
+#
+#   (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
+#       noncompliant, but you have some other compliant shell such as ksh or
+#       bash, then to run this script, type that shell name before the whole
+#       command line, like:
+#
+#           ksh Gradle
+#
+#       Busybox and similar reduced shells will NOT work, because this script
+#       requires all of these POSIX shell features:
+#         * functions;
+#         * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
+#           «${var#prefix}», «${var%suffix}», and «$( cmd )»;
+#         * compound commands having a testable exit status, especially «case»;
+#         * various built-in commands including «command», «set», and «ulimit».
+#
+#   Important for patching:
+#
+#   (2) This script targets any POSIX shell, so it avoids extensions provided
+#       by Bash, Ksh, etc; in particular arrays are avoided.
+#
+#       The "traditional" practice of packing multiple parameters into a
+#       space-separated string is a well documented source of bugs and security
+#       problems, so this is (mostly) avoided, by progressively accumulating
+#       options in "$@", and eventually passing that to Java.
+#
+#       Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
+#       and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
+#       see the in-line comments for details.
+#
+#       There are tweaks for specific operating systems such as AIX, CygWin,
+#       Darwin, MinGW, and NonStop.
+#
+#   (3) This script is generated from the Groovy template
+#       https://github.com/gradle/gradle/blob/master/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       within the Gradle project.
+#
+#       You can find Gradle at https://github.com/gradle/gradle/.
+#
+##############################################################################
+
+# Attempt to set APP_HOME
+
+# Resolve links: $0 may be a link
+app_path=$0
+
+# Need this for daisy-chained symlinks.
+while
+    APP_HOME=${app_path%"${app_path##*/}"}  # leaves a trailing /; empty if no leading path
+    [ -h "$app_path" ]
+do
+    ls=$( ls -ld "$app_path" )
+    link=${ls#*' -> '}
+    case $link in             #(
+      /*)   app_path=$link ;; #(
+      *)    app_path=$APP_HOME$link ;;
+    esac
+done
+
+APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit
+
+APP_NAME="Gradle"
+APP_BASE_NAME=${0##*/}
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD=maximum
+
+warn () {
+    echo "$*"
+} >&2
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+} >&2
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "$( uname )" in                #(
+  CYGWIN* )         cygwin=true  ;; #(
+  Darwin* )         darwin=true  ;; #(
+  MSYS* | MINGW* )  msys=true    ;; #(
+  NONSTOP* )        nonstop=true ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD=$JAVA_HOME/jre/sh/java
+    else
+        JAVACMD=$JAVA_HOME/bin/java
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD=java
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+    case $MAX_FD in #(
+      max*)
+        MAX_FD=$( ulimit -H -n ) ||
+            warn "Could not query maximum file descriptor limit"
+    esac
+    case $MAX_FD in  #(
+      '' | soft) :;; #(
+      *)
+        ulimit -n "$MAX_FD" ||
+            warn "Could not set maximum file descriptor limit to $MAX_FD"
+    esac
+fi
+
+# Collect all arguments for the java command, stacking in reverse order:
+#   * args from the command line
+#   * the main class name
+#   * -classpath
+#   * -D...appname settings
+#   * --module-path (only if needed)
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
+
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if "$cygwin" || "$msys" ; then
+    APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
+    CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
+
+    JAVACMD=$( cygpath --unix "$JAVACMD" )
+
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    for arg do
+        if
+            case $arg in                                #(
+              -*)   false ;;                            # don't mess with options #(
+              /?*)  t=${arg#/} t=/${t%%/*}              # looks like a POSIX filepath
+                    [ -e "$t" ] ;;                      #(
+              *)    false ;;
+            esac
+        then
+            arg=$( cygpath --path --ignore --mixed "$arg" )
+        fi
+        # Roll the args list around exactly as many times as the number of
+        # args, so each arg winds up back in the position where it started, but
+        # possibly modified.
+        #
+        # NB: a `for` loop captures its iteration list before it begins, so
+        # changing the positional parameters here affects neither the number of
+        # iterations, nor the values presented in `arg`.
+        shift                   # remove old arg
+        set -- "$@" "$arg"      # push replacement arg
+    done
+fi
+
+# Collect all arguments for the java command;
+#   * $DEFAULT_JVM_OPTS, $JAVA_OPTS, and $GRADLE_OPTS can contain fragments of
+#     shell script including quotes and variable substitutions, so put them in
+#     double quotes to make sure that they get re-expanded; and
+#   * put everything else in single quotes, so that it's not re-expanded.
+
+set -- \
+        "-Dorg.gradle.appname=$APP_BASE_NAME" \
+        -classpath "$CLASSPATH" \
+        org.gradle.wrapper.GradleWrapperMain \
+        "$@"
+
+# Use "xargs" to parse quoted args.
+#
+# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
+#
+# In Bash we could simply go:
+#
+#   readarray ARGS < <( xargs -n1 <<<"$var" ) &&
+#   set -- "${ARGS[@]}" "$@"
+#
+# but POSIX shell has neither arrays nor command substitution, so instead we
+# post-process each arg (as a line of input to sed) to backslash-escape any
+# character that might be a shell metacharacter, then use eval to reverse
+# that process (while maintaining the separation between arguments), and wrap
+# the whole thing up as a single "set" statement.
+#
+# This will of course break if any of these variables contains a newline or
+# an unmatched quote.
+#
+
+eval "set -- $(
+        printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
+        xargs -n1 |
+        sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
+        tr '\n' ' '
+    )" '"$@"'
+
+exec "$JAVACMD" "$@"

2024/07/netty_pingpong_demo1/netty_pingpong_demo1/gradlew.bat

@@ -0,0 +1,89 @@
+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      https://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+
+@if "%DEBUG%" == "" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%" == "" set DIRNAME=.
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if "%ERRORLEVEL%" == "0" goto execute
+
+echo.
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto execute
+
+echo.
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
+
+:end
+@rem End local scope for the variables with windows NT shell
+if "%ERRORLEVEL%"=="0" goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
+exit /b 1
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega

2024/07/netty_pingpong_demo1/netty_pingpong_demo1/settings.gradle.kts

@@ -0,0 +1,2 @@
+rootProject.name = "netty_pingpong_demo1"
+

2024/07/netty_pingpong_demo1/netty_pingpong_demo1/src/main/java/ch/polgrabia/demos/Main.java

@@ -0,0 +1,8 @@
+package ch.polgrabia.demos;
+
+public class Main {
+    public static void main(String[] args) {
+        new PingPongServer(8080)
+                .run();
+    }
+}

2024/07/netty_pingpong_demo1/netty_pingpong_demo1/src/main/java/ch/polgrabia/demos/PingPongHandler.java

@@ -0,0 +1,95 @@
+package ch.polgrabia.demos;
+
+import io.netty.buffer.ByteBuf;
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.channel.ChannelInboundHandlerAdapter;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.nio.charset.StandardCharsets;
+
+public class PingPongHandler extends ChannelInboundHandlerAdapter {
+    private static final Logger logger = LoggerFactory.getLogger(PingPongHandler.class);
+    public static final int ONE_READ_SIZE = 0x1000;
+
+    private final byte[] preamble = "Got request:%s"
+            .formatted(System.lineSeparator())
+            .getBytes(StandardCharsets.UTF_8);
+    private final byte[] payloadSeparator = "--------------------%s"
+            .formatted(System.lineSeparator())
+            .getBytes(StandardCharsets.UTF_8);
+
+    private final byte[] quiteCommand = "quit".getBytes(StandardCharsets.UTF_8);
+    private final byte[] quittingMessage = "Quitting...".getBytes(StandardCharsets.UTF_8);
+
+    private final byte[] inputLine = new byte[ONE_READ_SIZE];
+
+    @Override
+    public void channelRead(ChannelHandlerContext ctx, Object msg) {
+        var preambleBuffer = ctx.alloc().buffer(preamble.length);
+        ByteBuf separatorBuffer;
+        ByteBuf newlinesBuffer;
+        ByteBuf responseBuffer;
+
+        preambleBuffer.writeBytes(preamble);
+        ctx.write(preambleBuffer);
+
+        separatorBuffer = ctx.alloc().buffer(payloadSeparator.length);
+        separatorBuffer.writeBytes(payloadSeparator);
+        ctx.write(separatorBuffer);
+
+        var bbmsg = (ByteBuf) msg;
+
+        int read = 0;
+        while (bbmsg.isReadable()) {
+            int avail = bbmsg.readableBytes();
+            bbmsg.readBytes(inputLine,0, Math.min(avail, inputLine.length));
+
+            if (read == 0 && checkIfSubseqAtOffset(inputLine, quiteCommand)) {
+                responseBuffer = ctx.alloc().buffer(quittingMessage.length);
+                responseBuffer.writeBytes(quittingMessage);
+                ctx.flush();
+                ctx.close();
+                return;
+            }
+
+            int n = Math.min(avail, ONE_READ_SIZE);
+            read += n;
+            responseBuffer = ctx.alloc().buffer(n);
+            responseBuffer.writeBytes(inputLine, 0, n);
+            ctx.write(responseBuffer);
+        }
+
+
+        separatorBuffer = ctx.alloc().buffer(payloadSeparator.length);
+        separatorBuffer.writeBytes(payloadSeparator);
+        ctx.write(separatorBuffer);
+
+        newlinesBuffer = ctx.alloc().buffer(System.lineSeparator().getBytes(StandardCharsets.UTF_8).length * 2);
+        newlinesBuffer.writeBytes(System.lineSeparator().getBytes(StandardCharsets.UTF_8));
+        newlinesBuffer.writeBytes(System.lineSeparator().getBytes(StandardCharsets.UTF_8));
+        ctx.write(newlinesBuffer);
+
+        ctx.flush();
+    }
+
+    private boolean checkIfSubseqAtOffset(byte[] seq, byte[] subseq) {
+        if (seq.length < subseq.length) {
+            return false;
+        }
+
+        for (int i = 0; i < subseq.length; i++) {
+            if (seq[i] != subseq[i]) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
+    @Override
+    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
+        logger.error("Got exception", cause);
+        ctx.close();
+    }
+}

2024/07/netty_pingpong_demo1/netty_pingpong_demo1/src/main/java/ch/polgrabia/demos/PingPongServer.java

@@ -0,0 +1,45 @@
+package ch.polgrabia.demos;
+
+import io.netty.bootstrap.ServerBootstrap;
+import io.netty.channel.*;
+import io.netty.channel.nio.NioEventLoopGroup;
+import io.netty.channel.socket.nio.NioServerSocketChannel;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class PingPongServer implements Runnable {
+    private static final Logger logger = LoggerFactory.getLogger(PingPongHandler.class);
+    private final int port;
+
+    public PingPongServer(int port) {
+        this.port = port;
+    }
+
+    @Override
+    public void run() {
+        var bossGroup = new NioEventLoopGroup();
+        var workerGroup = new NioEventLoopGroup();
+        try {
+            ServerBootstrap sb = new ServerBootstrap();
+            sb.group(bossGroup, workerGroup)
+                    .channel(NioServerSocketChannel.class)
+                    .childHandler(new ChannelInitializer<>() {
+                        @Override
+                        protected void initChannel(Channel channel) {
+                            channel.pipeline().addLast(new PingPongHandler());
+                        }
+                    })
+                    .option(ChannelOption.SO_BACKLOG, 128)
+                    .childOption(ChannelOption.SO_KEEPALIVE, true);
+
+            ChannelFuture channelFuture = sb.bind(port)
+                    .addListener(
+                            (ChannelFutureListener) cf ->
+                                    logger.info("PingPongServer started on port: %d".formatted(port)))
+                    .sync();
+            channelFuture.channel().closeFuture().sync();
+        } catch (InterruptedException e) {
+            logger.error("We got interrupted", e);
+        }
+    }
+}