diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..8b04462
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,20 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+      - uses: actions/setup-java@v5
+        with:
+          distribution: temurin
+          java-version: 17
+      - uses: gradle/actions/setup-gradle@v4
+        with:
+          gradle-version: '8.5'
+      - run: gradle clean buildReleaseArtifacts
diff --git a/.github/workflows/docs.yml b/.github/workflows/docs.yml
new file mode 100644
index 0000000..6d04dce
--- /dev/null
+++ b/.github/workflows/docs.yml
@@ -0,0 +1,39 @@
+name: Documentation
+
+on:
+  push:
+    branches: [main]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+concurrency:
+  group: pages
+  cancel-in-progress: true
+
+jobs:
+  deploy:
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+      - uses: actions/setup-java@v5
+        with:
+          distribution: temurin
+          java-version: 17
+      - uses: gradle/actions/setup-gradle@v4
+        with:
+          gradle-version: '8.5'
+      - run: gradle javadoc
+      - uses: actions/configure-pages@v5
+      - uses: actions/upload-pages-artifact@v3
+        with:
+          path: build/docs/javadoc
+      - name: Deploy
+        id: deployment
+        uses: actions/deploy-pages@v4
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
new file mode 100644
index 0000000..65aaf8f
--- /dev/null
+++ b/.github/workflows/release.yml
@@ -0,0 +1,28 @@
+name: Release
+
+on:
+  push:
+    tags: ['v*']
+
+jobs:
+  release:
+    permissions:
+      contents: write
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+      - uses: actions/setup-java@v5
+        with:
+          distribution: temurin
+          java-version: 17
+      - uses: gradle/actions/setup-gradle@v4
+        with:
+          gradle-version: '8.5'
+      - name: Build release artifacts
+        run: gradle -PgithubReleaseTag=${GITHUB_REF_NAME} buildReleaseArtifacts
+      - uses: softprops/action-gh-release@v2
+        with:
+          files: |
+            release/DataNet.txt
+            release/DataNet.zip
+            release/DataNet.pdex
diff --git a/.gitignore b/.gitignore
index 524f096..8a1226d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,24 +1,17 @@
-# Compiled class file
+.gradle/
+build/
+release/
+library.properties
+.idea/
+.vscode/
+*.iml
 *.class
-
-# Log file
 *.log
-
-# BlueJ files
-*.ctxt
-
-# Mobile Tools for Java (J2ME)
-.mtj.tmp/
-
-# Package Files #
 *.jar
-*.war
-*.nar
-*.ear
 *.zip
-*.tar.gz
-*.rar
-
-# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
+*.pdex
+.DS_Store
 hs_err_pid*
 replay_pid*
+
+!gradle/wrapper/gradle-wrapper.jar
diff --git a/README.md b/README.md
index 632b490..1b1e015 100644
--- a/README.md
+++ b/README.md
@@ -1,17 +1,123 @@
-# datanet-processing
-DataNet Processing library — realtime pub/sub for sketches, visualizations, and installations.
+# DataNet for Processing
+
+Realtime pub/sub for networked sketches, visualizations, and installations. The library connects Processing 4 sketches to DataNet channels using the same protocol as the JavaScript, Python, and Arduino SDKs.
+
+## Features
+
+- JSON publish and subscribe with Processing `JSONObject` and `JSONArray`
+- Binary messages plus DMX frame helpers
+- Automatic authentication, heartbeat, reconnect, and subscription replay
+- Structured gateway errors
+- Authoritative channel presence
+- Message and event callbacks delivered on Processing's animation thread
+- No runtime dependencies beyond Processing 4 and Java 17
+
+## Install
+
+Once the library is accepted into Processing Contributions, install it from **Sketch → Import Library… → Manage Libraries…** and search for **DataNet**.
+
+Until then, download `DataNet.zip` from the latest GitHub release, unzip it into your Processing sketchbook's `libraries` directory, and restart Processing. The final path should be:
+
+```text
+<sketchbook>/libraries/DataNet/library/DataNet.jar
+```
+
+## Quick start
+
+```java
+import art.datanet.*;
+import processing.data.JSONObject;
+
+String API_KEY = "ak_your_project_key";
+String CHANNEL = "project.your-project-id.demo";
+DataNet datanet;
+
+void setup() {
+  size(720, 480);
+
+  datanet = new DataNet(this, DataNetConfig.builder(API_KEY)
+    .displayName("DataNet's Processing Sketch")
+    .build());
+
+  datanet.onError(error -> println(error.code() + ": " + error.getMessage()));
+  datanet.subscribe(CHANNEL, (data, meta) -> println(data));
+  datanet.connect();
+}
+
+void mousePressed() {
+  JSONObject message = new JSONObject();
+  message.setFloat("x", mouseX);
+  message.setFloat("y", mouseY);
+  datanet.publish(CHANNEL, message);
+}
+```
+
+Open **File → Examples → Contributed Libraries → DataNet** for complete JSON, binary/DMX, and presence examples.
+
+## API overview
+
+```java
+datanet.connect();
+datanet.disconnect();
+datanet.isConnected();
+
+datanet.publish(channel, jsonValue);
+datanet.subscribe(channel, (data, meta) -> { });
+datanet.unsubscribe(channel);
+
+datanet.publishBinary(channel, bytes);
+datanet.publishBinary(channel, bytes, "binary/custom", metadata);
+datanet.subscribeBinary(channel, (bytes, meta) -> { });
+datanet.publishDmx(channel, values);
+
+datanet.getPresence(channel, presence -> println(presence.occupancy()));
+```
+
+`MessageMeta` includes `channel`, `from`, and `timestamp`. `BinaryMessageMeta` also includes `contentType`, byte count, and optional protocol metadata.
+
+## Build and test
+
+Processing 4 ships with Java 17. If Java 17 is available in your shell:
+
+```sh
+./gradlew clean test
+./gradlew buildReleaseArtifacts
+```
+
+On macOS, you can use Processing's bundled JDK:
+
+```sh
+JAVA_HOME=/Applications/Processing.app/Contents/app/resources/jdk ./gradlew clean buildReleaseArtifacts
+```
+
+Release artifacts are written to `release/DataNet.zip`, `release/DataNet.txt`, and `release/DataNet.pdex`. To install a development build directly into the local sketchbook, run:
+
+```sh
+./gradlew deployToProcessingSketchbook
+```
+
+## Releasing
+
+1. Update `prettyVersion` and increment the integer `version` in `release.properties`.
+2. Run `./gradlew clean buildReleaseArtifacts`.
+3. Tag the merged commit, for example `v0.1.0`, and push the tag.
+4. GitHub Actions creates the release and attaches the `.zip`, `.txt`, and `.pdex` files required by Processing Contributions.
+5. For the first release, submit the stable `DataNet.txt` URL to the Processing Contributions repository. Later releases are discovered through the incremented metadata.
+
+## Compatibility
+
+- Processing 4
+- macOS, Windows, and Linux
+- DataNet protocol: JSON and base64 binary WebSocket envelopes
 
 ## About
 
 DataNet is developed and supported by [Studio Jordan Shaw](https://www.jordanshaw.com), a creative technology studio building tools for realtime, networked, and physical-digital work.
 
-- DataNet: [datanet.art](https://datanet.art)
-- Studio: [jordanshaw.com](https://www.jordanshaw.com)
-- Instagram: [@jshaw3](https://www.instagram.com/jshaw3)
-- GitHub: [datanet-art](https://github.com/datanet-art)
-- Source: [datanet-processing](https://github.com/datanet-art/datanet-processing)
-- Examples: [datanet-examples](https://github.com/datanet-art/datanet-examples)
+- [DataNet](https://datanet.art)
+- [GitHub organization](https://github.com/datanet-art)
+- [Cross-platform examples](https://github.com/datanet-art/datanet-examples)
 
 ## License
 
-MIT
+[MIT](LICENSE)
diff --git a/build.gradle.kts b/build.gradle.kts
new file mode 100644
index 0000000..a2b33f7
--- /dev/null
+++ b/build.gradle.kts
@@ -0,0 +1,150 @@
+import java.util.Properties
+import org.gradle.internal.os.OperatingSystem
+
+plugins {
+    java
+}
+
+java {
+    toolchain {
+        languageVersion = JavaLanguageVersion.of(17)
+    }
+    withSourcesJar()
+}
+
+val libraryProperties = Properties().apply {
+    load(rootProject.file("release.properties").inputStream())
+}
+
+version = if (project.hasProperty("githubReleaseTag")) {
+    project.property("githubReleaseTag").toString().removePrefix("v")
+} else {
+    libraryProperties.getProperty("prettyVersion")
+}
+group = "art.datanet"
+
+val libName = "DataNet"
+val userHome = System.getProperty("user.home")
+val currentOS = OperatingSystem.current()
+val sketchbookLocation = when {
+    currentOS.isMacOsX -> if (file("$userHome/Documents/Processing/sketchbook").isDirectory) {
+        "$userHome/Documents/Processing/sketchbook"
+    } else {
+        "$userHome/Documents/Processing"
+    }
+    currentOS.isWindows -> {
+        val documents = if (file("$userHome/My Documents").isDirectory) {
+            "$userHome/My Documents"
+        } else {
+            "$userHome/Documents"
+        }
+        if (file("$documents/Processing/sketchbook").isDirectory) "$documents/Processing/sketchbook" else "$documents/Processing"
+    }
+    else -> "$userHome/sketchbook"
+}
+
+repositories {
+    mavenCentral()
+    maven { url = uri("https://jogamp.org/deployment/maven/") }
+}
+
+dependencies {
+    compileOnly("org.processing:core:4.3.1")
+    testImplementation("org.processing:core:4.3.1")
+    testImplementation(platform("org.junit:junit-bom:5.10.2"))
+    testImplementation("org.junit.jupiter:junit-jupiter")
+}
+
+tasks.test {
+    useJUnitPlatform()
+}
+
+tasks.jar {
+    archiveBaseName.set(libName)
+    archiveClassifier.set("")
+    archiveVersion.set("")
+}
+
+tasks.javadoc {
+    options.encoding = "UTF-8"
+    (options as StandardJavadocDocletOptions).addBooleanOption("Xdoclint:none", true)
+}
+
+val releaseRoot = layout.projectDirectory.dir("release")
+val releaseDirectory = releaseRoot.dir(libName)
+
+val writeLibraryProperties by tasks.registering(WriteProperties::class) {
+    group = "processing"
+    destinationFile = project.file("library.properties")
+    property("name", libraryProperties.getProperty("name"))
+    property("version", libraryProperties.getProperty("version"))
+    property("prettyVersion", project.version)
+    property("authors", libraryProperties.getProperty("authors"))
+    property("url", libraryProperties.getProperty("url"))
+    property("categories", libraryProperties.getProperty("categories"))
+    property("sentence", libraryProperties.getProperty("sentence"))
+    property("paragraph", libraryProperties.getProperty("paragraph"))
+    property("minRevision", libraryProperties.getProperty("minRevision"))
+    property("maxRevision", libraryProperties.getProperty("maxRevision"))
+}
+
+val stageRelease by tasks.registering(Sync::class) {
+    group = "processing"
+    dependsOn(tasks.build, tasks.javadoc, writeLibraryProperties)
+    into(releaseDirectory)
+    from(tasks.jar) { into("library") }
+    from(tasks.javadoc) { into("reference") }
+    from("library.properties")
+    from("README.md")
+    from("LICENSE")
+    from("examples") { into("examples") }
+    from("src/main/java") { into("src") }
+}
+
+val packageRelease by tasks.registering(Zip::class) {
+    group = "processing"
+    dependsOn(stageRelease)
+    archiveFileName.set("$libName.zip")
+    destinationDirectory.set(releaseRoot.asFile)
+    from(releaseDirectory) { into(libName) }
+}
+
+val writeContributionMetadata by tasks.registering {
+    group = "processing"
+    dependsOn(writeLibraryProperties)
+    inputs.file("library.properties")
+    outputs.file(releaseRoot.file("$libName.txt"))
+    doLast {
+        copy {
+            from("library.properties")
+            into(releaseRoot)
+            rename("library.properties", "$libName.txt")
+        }
+    }
+}
+
+val duplicateZipToPdex by tasks.registering {
+    group = "processing"
+    dependsOn(packageRelease)
+    inputs.file(releaseRoot.file("$libName.zip"))
+    outputs.file(releaseRoot.file("$libName.pdex"))
+    doLast {
+        copy {
+            from(releaseRoot.file("$libName.zip"))
+            into(releaseRoot)
+            rename("$libName.zip", "$libName.pdex")
+        }
+    }
+}
+
+tasks.register("buildReleaseArtifacts") {
+    group = "processing"
+    dependsOn(packageRelease, writeContributionMetadata, duplicateZipToPdex)
+}
+
+tasks.register<Sync>("deployToProcessingSketchbook") {
+    group = "processing"
+    dependsOn(stageRelease)
+    from(releaseDirectory)
+    into("$sketchbookLocation/libraries/$libName")
+}
diff --git a/examples/BasicPublishSubscribe/BasicPublishSubscribe.pde b/examples/BasicPublishSubscribe/BasicPublishSubscribe.pde
new file mode 100644
index 0000000..17b35bb
--- /dev/null
+++ b/examples/BasicPublishSubscribe/BasicPublishSubscribe.pde
@@ -0,0 +1,47 @@
+import art.datanet.*;
+import processing.data.JSONObject;
+
+// Replace these two values with your DataNet project API key and channel.
+String API_KEY = "ak_your_project_key";
+String CHANNEL = "project.your-project-id.demo";
+
+DataNet datanet;
+float remoteX;
+float remoteY;
+boolean online;
+
+void setup() {
+  size(720, 480);
+
+  datanet = new DataNet(this, DataNetConfig.builder(API_KEY)
+    .displayName("DataNet's Processing Sketch")
+    .build());
+
+  datanet.onConnect(() -> online = true);
+  datanet.onDisconnect(() -> online = false);
+  datanet.onError(error -> println(error.code() + ": " + error.getMessage()));
+
+  datanet.subscribe(CHANNEL, (data, meta) -> {
+    if (data instanceof JSONObject point) {
+      remoteX = point.getFloat("x", remoteX);
+      remoteY = point.getFloat("y", remoteY);
+    }
+  });
+
+  datanet.connect();
+}
+
+void draw() {
+  background(18);
+  fill(online ? color(92, 230, 162) : color(255, 184, 92));
+  circle(remoteX, remoteY, 36);
+  fill(240);
+  text(online ? "Connected — move your mouse" : "Connecting…", 20, 30);
+}
+
+void mouseMoved() {
+  JSONObject point = new JSONObject();
+  point.setFloat("x", mouseX);
+  point.setFloat("y", mouseY);
+  datanet.publish(CHANNEL, point);
+}
diff --git a/examples/BinaryData/BinaryData.pde b/examples/BinaryData/BinaryData.pde
new file mode 100644
index 0000000..4b9eaf4
--- /dev/null
+++ b/examples/BinaryData/BinaryData.pde
@@ -0,0 +1,26 @@
+import art.datanet.*;
+
+String API_KEY = "ak_your_project_key";
+String CHANNEL = "project.your-project-id.lights";
+
+DataNet datanet;
+int[] dmx = new int[512];
+
+void setup() {
+  size(720, 240);
+  datanet = new DataNet(this, API_KEY);
+  datanet.onError(error -> println(error.code() + ": " + error.getMessage()));
+  datanet.connect();
+}
+
+void draw() {
+  background(18);
+  int level = constrain((int) map(mouseX, 0, width, 0, 255), 0, 255);
+  dmx[0] = level;
+  dmx[1] = 255 - level;
+  dmx[2] = 160;
+
+  fill(dmx[0], dmx[1], dmx[2]);
+  rect(0, 0, width, height);
+  datanet.publishDmx(CHANNEL, dmx);
+}
diff --git a/examples/Presence/Presence.pde b/examples/Presence/Presence.pde
new file mode 100644
index 0000000..d937342
--- /dev/null
+++ b/examples/Presence/Presence.pde
@@ -0,0 +1,31 @@
+import art.datanet.*;
+
+String API_KEY = "ak_your_project_key";
+String CHANNEL = "project.your-project-id.demo";
+
+DataNet datanet;
+int occupancy;
+int lastCheck;
+
+void setup() {
+  size(600, 320);
+  textAlign(CENTER, CENTER);
+  datanet = new DataNet(this, API_KEY);
+  datanet.onError(error -> println(error.code() + ": " + error.getMessage()));
+  datanet.onConnect(() -> refreshPresence());
+  datanet.connect();
+}
+
+void draw() {
+  background(18);
+  fill(240);
+  textSize(22);
+  text(occupancy + " connected device" + (occupancy == 1 ? "" : "s"), width / 2, height / 2);
+
+  if (datanet.isConnected() && millis() - lastCheck > 3000) refreshPresence();
+}
+
+void refreshPresence() {
+  lastCheck = millis();
+  datanet.getPresence(CHANNEL, presence -> occupancy = presence.occupancy());
+}
diff --git a/gradle/wrapper/gradle-wrapper.jar b/gradle/wrapper/gradle-wrapper.jar
new file mode 100644
index 0000000..d64cd49
Binary files /dev/null and b/gradle/wrapper/gradle-wrapper.jar differ
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
new file mode 100644
index 0000000..1af9e09
--- /dev/null
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -0,0 +1,7 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.5-bin.zip
+networkTimeout=10000
+validateDistributionUrl=true
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
diff --git a/gradlew b/gradlew
new file mode 100755
index 0000000..1aa94a4
--- /dev/null
+++ b/gradlew
@@ -0,0 +1,249 @@
+#!/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/HEAD/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
+
+# This is normally unused
+# shellcheck disable=SC2034
+APP_BASE_NAME=${0##*/}
+# Discard cd standard output in case $CDPATH is set (https://github.com/gradle/gradle/issues/25036)
+APP_HOME=$( cd "${APP_HOME:-./}" > /dev/null && pwd -P ) || exit
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD=maximum
+
+warn () {
+    echo "$*"
+} >&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: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD=java
+    if ! command -v java >/dev/null 2>&1
+    then
+        die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+fi
+
+# Increase the maximum file descriptors if we can.
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+    case $MAX_FD in #(
+      max*)
+        # In POSIX sh, ulimit -H is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
+        MAX_FD=$( ulimit -H -n ) ||
+            warn "Could not query maximum file descriptor limit"
+    esac
+    case $MAX_FD in  #(
+      '' | soft) :;; #(
+      *)
+        # In POSIX sh, ulimit -n is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
+        ulimit -n "$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
+
+
+# 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"'
+
+# Collect all arguments for the java command:
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, JAVA_OPTS, and optsEnvironmentVar are not allowed to contain shell fragments,
+#     and any embedded shellness will be escaped.
+#   * For example: A user cannot expect ${Hostname} to be expanded, as it is an environment variable and will be
+#     treated as '${Hostname}' itself on the command line.
+
+set -- \
+        "-Dorg.gradle.appname=$APP_BASE_NAME" \
+        -classpath "$CLASSPATH" \
+        org.gradle.wrapper.GradleWrapperMain \
+        "$@"
+
+# Stop when "xargs" is not available.
+if ! command -v xargs >/dev/null 2>&1
+then
+    die "xargs is not available"
+fi
+
+# Use "xargs" to parse quoted args.
+#
+# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
+#
+# In Bash we could simply go:
+#
+#   readarray ARGS < <( xargs -n1 <<<"$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 "$JAVACMD" "$@"
diff --git a/gradlew.bat b/gradlew.bat
new file mode 100644
index 0000000..93e3f59
--- /dev/null
+++ b/gradlew.bat
@@ -0,0 +1,92 @@
+@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=.
+@rem This is normally unused
+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% equ 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% equ 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!
+set EXIT_CODE=%ERRORLEVEL%
+if %EXIT_CODE% equ 0 set EXIT_CODE=1
+if not ""=="%GRADLE_EXIT_CONSOLE%" exit %EXIT_CODE%
+exit /b %EXIT_CODE%
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega
diff --git a/release.properties b/release.properties
new file mode 100644
index 0000000..037b514
--- /dev/null
+++ b/release.properties
@@ -0,0 +1,10 @@
+name=DataNet
+version=1
+prettyVersion=0.1.0
+authors=[DataNet](https://datanet.art), [Studio Jordan Shaw](https://www.jordanshaw.com)
+url=https://datanet-art.github.io/datanet-processing/
+categories=Data,I/O
+sentence=Realtime pub/sub for networked sketches, visualizations, and installations.
+paragraph=Connect Processing 4 sketches to browsers, phones, hardware, and other creative tools through DataNet channels. Supports JSON, binary data, reconnects, and presence on macOS, Windows, and Linux.
+minRevision=0
+maxRevision=0
diff --git a/settings.gradle.kts b/settings.gradle.kts
new file mode 100644
index 0000000..e7cbe8d
--- /dev/null
+++ b/settings.gradle.kts
@@ -0,0 +1,5 @@
+plugins {
+    id("org.gradle.toolchains.foojay-resolver-convention") version "0.9.0"
+}
+
+rootProject.name = "datanet-processing"
diff --git a/src/main/java/art/datanet/BinaryMessageHandler.java b/src/main/java/art/datanet/BinaryMessageHandler.java
new file mode 100644
index 0000000..09b8fee
--- /dev/null
+++ b/src/main/java/art/datanet/BinaryMessageHandler.java
@@ -0,0 +1,7 @@
+package art.datanet;
+
+/** Receives raw bytes and their message metadata. */
+@FunctionalInterface
+public interface BinaryMessageHandler {
+  void onMessage(byte[] data, BinaryMessageMeta meta);
+}
diff --git a/src/main/java/art/datanet/BinaryMessageMeta.java b/src/main/java/art/datanet/BinaryMessageMeta.java
new file mode 100644
index 0000000..e4b3442
--- /dev/null
+++ b/src/main/java/art/datanet/BinaryMessageMeta.java
@@ -0,0 +1,12 @@
+package art.datanet;
+
+import processing.data.JSONObject;
+
+/** Sender, format, and timing information accompanying a binary message. */
+public record BinaryMessageMeta(
+    String channel,
+    String from,
+    long timestamp,
+    String contentType,
+    int bytes,
+    JSONObject metadata) {}
diff --git a/src/main/java/art/datanet/DataNet.java b/src/main/java/art/datanet/DataNet.java
new file mode 100644
index 0000000..ace2247
--- /dev/null
+++ b/src/main/java/art/datanet/DataNet.java
@@ -0,0 +1,622 @@
+package art.datanet;
+
+import java.net.URI;
+import java.net.URLEncoder;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.net.http.WebSocket;
+import java.nio.ByteBuffer;
+import java.nio.charset.StandardCharsets;
+import java.time.Duration;
+import java.util.ArrayList;
+import java.util.Base64;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Set;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionStage;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.concurrent.CopyOnWriteArraySet;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.ScheduledFuture;
+import java.util.concurrent.ThreadFactory;
+import java.util.concurrent.TimeUnit;
+import java.util.function.Consumer;
+import processing.core.PApplet;
+import processing.data.JSONArray;
+import processing.data.JSONObject;
+
+/**
+ * Realtime DataNet client for Processing 4.
+ *
+ * <p>Network work runs in the background. Message, connection, error, and convenience presence
+ * callbacks run during Processing's {@code pre()} phase, immediately before {@code draw()}.</p>
+ */
+public final class DataNet implements AutoCloseable {
+  public static final String VERSION = "0.1.0";
+  public static final String CONTENT_TYPE_BINARY = "application/octet-stream";
+  public static final String CONTENT_TYPE_DMX = "binary/dmx";
+  public static final String CONTENT_TYPE_ARTNET = "binary/artnet";
+
+  private final PApplet parent;
+  private final DataNetConfig config;
+  private final HttpClient httpClient;
+  private final ScheduledExecutorService scheduler;
+  private final ConcurrentLinkedQueue<Runnable> callbackQueue = new ConcurrentLinkedQueue<>();
+  private final Map<String, Set<MessageHandler>> messageHandlers = new ConcurrentHashMap<>();
+  private final Map<String, Set<BinaryMessageHandler>> binaryHandlers = new ConcurrentHashMap<>();
+  private final Object connectionLock = new Object();
+
+  private volatile WebSocket webSocket;
+  private volatile String jwt;
+  private volatile boolean connected;
+  private volatile boolean connecting;
+  private volatile boolean explicitlyDisconnected = true;
+  private volatile boolean fatalError;
+  private volatile int reconnectAttempts;
+  private volatile long activeGeneration;
+  private volatile long handledDisconnectGeneration = -1;
+  private volatile CompletableFuture<DataNet> connectFuture;
+  private volatile ScheduledFuture<?> heartbeatTask;
+  private volatile ScheduledFuture<?> reconnectTask;
+  private volatile Runnable connectHandler;
+  private volatile Runnable disconnectHandler;
+  private volatile ErrorHandler errorHandler;
+
+  /** Create a client with default endpoints and identity settings. */
+  public DataNet(PApplet parent, String apiKey) {
+    this(parent, DataNetConfig.builder(apiKey).build());
+  }
+
+  /** Create a client with custom identity, endpoint, or reconnect settings. */
+  public DataNet(PApplet parent, DataNetConfig config) {
+    this.parent = parent;
+    this.config = Objects.requireNonNull(config, "config");
+    ThreadFactory threads = runnable -> {
+      Thread thread = new Thread(runnable, "datanet-processing");
+      thread.setDaemon(true);
+      return thread;
+    };
+    this.scheduler = Executors.newSingleThreadScheduledExecutor(threads);
+    this.httpClient = HttpClient.newBuilder()
+        .connectTimeout(config.requestTimeout)
+        .executor(scheduler)
+        .build();
+    if (parent != null) {
+      parent.registerMethod("pre", this);
+      parent.registerMethod("dispose", this);
+    }
+  }
+
+  /** Connect asynchronously. Calling this again while connected is harmless. */
+  public CompletableFuture<DataNet> connect() {
+    synchronized (connectionLock) {
+      if (connected) return CompletableFuture.completedFuture(this);
+      if (connecting && connectFuture != null) return connectFuture;
+      explicitlyDisconnected = false;
+      fatalError = false;
+      reconnectAttempts = 0;
+      connecting = true;
+      connectFuture = new CompletableFuture<>();
+      authenticateAndOpen();
+      return connectFuture;
+    }
+  }
+
+  /** Disconnect and disable automatic reconnect until {@link #connect()} is called again. */
+  public void disconnect() {
+    WebSocket socket;
+    boolean notify;
+    synchronized (connectionLock) {
+      explicitlyDisconnected = true;
+      connecting = false;
+      activeGeneration++;
+      socket = webSocket;
+      webSocket = null;
+      notify = connected;
+      connected = false;
+      cancel(reconnectTask);
+      reconnectTask = null;
+      stopHeartbeat();
+      if (connectFuture != null && !connectFuture.isDone()) {
+        connectFuture.completeExceptionally(new DataNetError("disconnected", "DataNet: connection cancelled"));
+      }
+    }
+    if (socket != null) socket.sendClose(WebSocket.NORMAL_CLOSURE, "client disconnect");
+    if (notify) dispatch(this::notifyDisconnected);
+  }
+
+  public boolean isConnected() {
+    return connected;
+  }
+
+  /** Run queued callbacks on Processing's animation thread. Called automatically by Processing. */
+  public void pre() {
+    Runnable callback;
+    while ((callback = callbackQueue.poll()) != null) {
+      try {
+        callback.run();
+      } catch (RuntimeException exception) {
+        System.err.println("DataNet callback failed: " + exception.getMessage());
+        exception.printStackTrace();
+      }
+    }
+  }
+
+  /** Release network resources. Called automatically when the sketch exits. */
+  public void dispose() {
+    disconnect();
+    scheduler.shutdownNow();
+    if (parent != null) {
+      parent.unregisterMethod("pre", this);
+      parent.unregisterMethod("dispose", this);
+    }
+  }
+
+  @Override
+  public void close() {
+    dispose();
+  }
+
+  public DataNet onConnect(Runnable handler) {
+    this.connectHandler = handler;
+    return this;
+  }
+
+  public DataNet onDisconnect(Runnable handler) {
+    this.disconnectHandler = handler;
+    return this;
+  }
+
+  public DataNet onError(ErrorHandler handler) {
+    this.errorHandler = handler;
+    return this;
+  }
+
+  /** Subscribe to JSON-compatible messages on a channel. */
+  public DataNet subscribe(String channel, MessageHandler handler) {
+    channel = Protocol.requireChannel(channel);
+    Objects.requireNonNull(handler, "handler");
+    boolean first = !hasHandlers(channel);
+    messageHandlers.computeIfAbsent(channel, ignored -> new CopyOnWriteArraySet<>()).add(handler);
+    if (first) send(Protocol.subscribe(channel));
+    return this;
+  }
+
+  /** Remove one JSON handler. The network subscription remains while another handler is present. */
+  public DataNet unsubscribe(String channel, MessageHandler handler) {
+    channel = Protocol.requireChannel(channel);
+    Set<MessageHandler> handlers = messageHandlers.get(channel);
+    if (handlers != null) {
+      handlers.remove(handler);
+      if (handlers.isEmpty()) messageHandlers.remove(channel, handlers);
+    }
+    unsubscribeIfUnused(channel);
+    return this;
+  }
+
+  /** Remove every JSON handler for a channel. */
+  public DataNet unsubscribe(String channel) {
+    channel = Protocol.requireChannel(channel);
+    messageHandlers.remove(channel);
+    unsubscribeIfUnused(channel);
+    return this;
+  }
+
+  /** Subscribe to binary messages on a channel. */
+  public DataNet subscribeBinary(String channel, BinaryMessageHandler handler) {
+    channel = Protocol.requireChannel(channel);
+    Objects.requireNonNull(handler, "handler");
+    boolean first = !hasHandlers(channel);
+    binaryHandlers.computeIfAbsent(channel, ignored -> new CopyOnWriteArraySet<>()).add(handler);
+    if (first) send(Protocol.subscribe(channel));
+    return this;
+  }
+
+  public DataNet unsubscribeBinary(String channel, BinaryMessageHandler handler) {
+    channel = Protocol.requireChannel(channel);
+    Set<BinaryMessageHandler> handlers = binaryHandlers.get(channel);
+    if (handlers != null) {
+      handlers.remove(handler);
+      if (handlers.isEmpty()) binaryHandlers.remove(channel, handlers);
+    }
+    unsubscribeIfUnused(channel);
+    return this;
+  }
+
+  public DataNet unsubscribeBinary(String channel) {
+    channel = Protocol.requireChannel(channel);
+    binaryHandlers.remove(channel);
+    unsubscribeIfUnused(channel);
+    return this;
+  }
+
+  /** Publish any Processing JSON object, array, string, number, boolean, or null value. */
+  public DataNet publish(String channel, Object data) {
+    send(Protocol.publish(Protocol.requireChannel(channel), data));
+    return this;
+  }
+
+  /** Publish raw bytes with the default application/octet-stream content type. */
+  public DataNet publishBinary(String channel, byte[] data) {
+    return publishBinary(channel, data, CONTENT_TYPE_BINARY, null);
+  }
+
+  /** Publish raw bytes with format and optional protocol metadata. */
+  public DataNet publishBinary(String channel, byte[] data, String contentType, JSONObject metadata) {
+    Objects.requireNonNull(data, "data");
+    if (contentType == null || contentType.isBlank()) contentType = CONTENT_TYPE_BINARY;
+    send(Protocol.publishBinary(Protocol.requireChannel(channel), data, contentType, metadata));
+    return this;
+  }
+
+  /** Build and publish a zero-padded DMX frame of 1 to 512 channels. */
+  public DataNet publishDmx(String channel, int[] values) {
+    Objects.requireNonNull(values, "values");
+    if (values.length > 512) throw new IllegalArgumentException("DMX data cannot exceed 512 channels");
+    byte[] frame = new byte[512];
+    for (int index = 0; index < values.length; index++) {
+      frame[index] = (byte) Math.max(0, Math.min(255, values[index]));
+    }
+    return publishBinary(channel, frame, CONTENT_TYPE_DMX, null);
+  }
+
+  /** Query authoritative channel occupancy. The returned future completes off the animation thread. */
+  public CompletableFuture<PresenceResult> getPresence(String channel) {
+    channel = Protocol.requireChannel(channel);
+    String token = jwt;
+    if (token == null) {
+      return CompletableFuture.failedFuture(
+          new DataNetError("not_connected", "DataNet: connect before requesting presence"));
+    }
+    String projectId = projectIdFromJwt(token);
+    String query = "channel=" + encode(channel)
+        + (projectId == null ? "" : "&projectId=" + encode(projectId));
+    URI endpoint = config.apiUrl.resolve("/presence?" + query);
+    HttpRequest request = HttpRequest.newBuilder(endpoint)
+        .timeout(Duration.ofSeconds(8))
+        .header("Authorization", "Bearer " + token)
+        .GET()
+        .build();
+    String requestedChannel = channel;
+    return httpClient.sendAsync(request, HttpResponse.BodyHandlers.ofString(StandardCharsets.UTF_8))
+        .handle((response, failure) -> {
+          if (failure != null) {
+            throw new DataNetError("presence_failed", "DataNet: presence request failed", unwrap(failure));
+          }
+          if (response.statusCode() < 200 || response.statusCode() >= 300) {
+            String detail = response.body();
+            try {
+              JSONObject body = JSONObject.parse(response.body());
+              detail = body.getString("error", detail);
+            } catch (RuntimeException ignored) {
+              // Preserve the response body when it is not JSON.
+            }
+            String code = response.statusCode() == 403 ? "presence_forbidden" : "presence_failed";
+            throw new DataNetError(code,
+                "DataNet: presence request failed (" + response.statusCode() + " " + detail + ")",
+                requestedChannel, null, null, response.statusCode(), null, null);
+          }
+          JSONObject body = JSONObject.parse(response.body());
+          int occupancy = body.getInt("occupancy", body.getInt("count", 0));
+          List<String> members = new ArrayList<>();
+          if (body.hasKey("members") && !body.isNull("members")) {
+            JSONArray list = body.getJSONArray("members");
+            for (int index = 0; index < list.size(); index++) {
+              Object member = list.get(index);
+              if (member instanceof String value) members.add(value);
+            }
+          }
+          return new PresenceResult(occupancy, members);
+        });
+  }
+
+  /** Query presence and invoke handlers on Processing's animation thread. */
+  public DataNet getPresence(String channel, PresenceHandler handler) {
+    Objects.requireNonNull(handler, "handler");
+    getPresence(channel).whenComplete((presence, failure) -> {
+      if (failure != null) dispatch(() -> notifyError(asDataNetError(failure, "presence_failed")));
+      else dispatch(() -> handler.onPresence(presence));
+    });
+    return this;
+  }
+
+  private void authenticateAndOpen() {
+    JSONObject body = new JSONObject().setString("apiKey", config.apiKey);
+    if (config.deviceId != null) body.setString("deviceId", config.deviceId);
+    if (config.clientId != null) body.setString("clientId", config.clientId);
+    if (config.displayName != null) body.setString("deviceName", config.displayName);
+    HttpRequest request = HttpRequest.newBuilder(config.apiUrl.resolve("/auth/token"))
+        .timeout(config.requestTimeout)
+        .header("Content-Type", "application/json")
+        .POST(HttpRequest.BodyPublishers.ofString(body.toString(), StandardCharsets.UTF_8))
+        .build();
+    httpClient.sendAsync(request, HttpResponse.BodyHandlers.ofString(StandardCharsets.UTF_8))
+        .whenComplete((response, failure) -> {
+          if (failure != null) {
+            failConnect(new DataNetError("auth_failed", "DataNet: authentication failed", unwrap(failure)));
+            return;
+          }
+          if (response.statusCode() < 200 || response.statusCode() >= 300) {
+            failConnect(new DataNetError("auth_failed",
+                "DataNet: authentication failed (HTTP " + response.statusCode() + ")",
+                null, null, null, response.statusCode(), null, null));
+            return;
+          }
+          try {
+            String token = JSONObject.parse(response.body()).getString("token");
+            if (token == null || token.isBlank()) throw new IllegalArgumentException("missing token");
+            jwt = token;
+            openSocket(token);
+          } catch (RuntimeException exception) {
+            failConnect(new DataNetError("auth_failed", "DataNet: authentication returned an invalid token", exception));
+          }
+        });
+  }
+
+  private void openSocket(String token) {
+    final long generation;
+    synchronized (connectionLock) {
+      if (explicitlyDisconnected || fatalError) return;
+      generation = ++activeGeneration;
+      handledDisconnectGeneration = -1;
+    }
+    SocketListener listener = new SocketListener(generation);
+    httpClient.newWebSocketBuilder()
+        .connectTimeout(config.requestTimeout)
+        .subprotocols("bearer", token)
+        .buildAsync(config.wsUrl, listener)
+        .whenComplete((socket, failure) -> {
+          if (failure != null) handleSocketEnded(generation,
+              new DataNetError("connection_failed", "DataNet: WebSocket connection failed", unwrap(failure)));
+        });
+  }
+
+  private void handleText(long generation, String text) {
+    if (generation != activeGeneration) return;
+    final JSONObject message;
+    try {
+      message = JSONObject.parse(text);
+    } catch (RuntimeException exception) {
+      dispatch(() -> notifyError(new DataNetError("invalid_message", "DataNet: invalid JSON message", exception)));
+      return;
+    }
+    String type = message.getString("type", "");
+    String operation = message.getString("op", "");
+    if ("connected".equals(type)) {
+      connected = true;
+      connecting = false;
+      reconnectAttempts = 0;
+      startHeartbeat();
+      replaySubscriptions();
+      CompletableFuture<DataNet> pending = connectFuture;
+      if (pending != null && !pending.isDone()) pending.complete(this);
+      dispatch(this::notifyConnected);
+      return;
+    }
+    if ("error".equals(type)) {
+      DataNetError error = Protocol.gatewayError(message);
+      dispatch(() -> notifyError(error));
+      if ("device_limit_reached".equals(error.code())) {
+        fatalError = true;
+        CompletableFuture<DataNet> pending = connectFuture;
+        if (pending != null && !pending.isDone()) pending.completeExceptionally(error);
+        WebSocket socket = webSocket;
+        if (socket != null) socket.abort();
+        handleSocketEnded(generation, null);
+      }
+      return;
+    }
+    if (!"message".equals(type) && !"pub".equals(operation)) return;
+    String channel = message.getString("ch", "");
+    String from = message.getString("from", "");
+    long timestamp = message.getLong("ts", System.currentTimeMillis());
+    if (message.getBoolean("bin", false)) {
+      try {
+        byte[] bytes = Protocol.decodeBinary(message.getString("b64", ""));
+        JSONObject metadata = message.hasKey("meta") && !message.isNull("meta")
+            ? message.getJSONObject("meta") : null;
+        BinaryMessageMeta meta = new BinaryMessageMeta(
+            channel,
+            from,
+            timestamp,
+            message.getString("ct", CONTENT_TYPE_BINARY),
+            message.getInt("bytes", bytes.length),
+            metadata);
+        Set<BinaryMessageHandler> handlers = binaryHandlers.get(channel);
+        if (handlers != null) {
+          for (BinaryMessageHandler handler : handlers) {
+            dispatch(() -> handler.onMessage(bytes.clone(), meta));
+          }
+        }
+      } catch (RuntimeException exception) {
+        dispatch(() -> notifyError(new DataNetError("invalid_binary", "DataNet: invalid binary message", exception)));
+      }
+      return;
+    }
+    Object data = message.hasKey("d") ? message.get("d") : null;
+    MessageMeta meta = new MessageMeta(channel, from, timestamp);
+    Set<MessageHandler> handlers = messageHandlers.get(channel);
+    if (handlers != null) {
+      for (MessageHandler handler : handlers) dispatch(() -> handler.onMessage(data, meta));
+    }
+  }
+
+  private void handleSocketEnded(long generation, DataNetError error) {
+    boolean wasConnected;
+    synchronized (connectionLock) {
+      if (generation != activeGeneration || handledDisconnectGeneration == generation) return;
+      handledDisconnectGeneration = generation;
+      wasConnected = connected;
+      connected = false;
+      connecting = false;
+      webSocket = null;
+      stopHeartbeat();
+    }
+    if (error != null) dispatch(() -> notifyError(error));
+    if (wasConnected) dispatch(this::notifyDisconnected);
+    if (!explicitlyDisconnected && !fatalError) scheduleReconnect();
+  }
+
+  private void scheduleReconnect() {
+    synchronized (connectionLock) {
+      if (reconnectAttempts >= config.maxReconnectAttempts) {
+        DataNetError error = new DataNetError("reconnect_failed", "DataNet: maximum reconnect attempts reached");
+        if (connectFuture != null && !connectFuture.isDone()) connectFuture.completeExceptionally(error);
+        dispatch(() -> notifyError(error));
+        return;
+      }
+      reconnectAttempts++;
+      long delay = Math.min(30_000L, 1_000L << Math.min(reconnectAttempts - 1, 5));
+      connecting = true;
+      reconnectTask = scheduler.schedule(this::authenticateAndOpen, delay, TimeUnit.MILLISECONDS);
+    }
+  }
+
+  private void failConnect(DataNetError error) {
+    connecting = false;
+    CompletableFuture<DataNet> pending = connectFuture;
+    if (pending != null && !pending.isDone()) pending.completeExceptionally(error);
+    dispatch(() -> notifyError(error));
+  }
+
+  private void replaySubscriptions() {
+    Set<String> channels = ConcurrentHashMap.newKeySet();
+    channels.addAll(messageHandlers.keySet());
+    channels.addAll(binaryHandlers.keySet());
+    for (String channel : channels) send(Protocol.subscribe(channel));
+  }
+
+  private boolean hasHandlers(String channel) {
+    Set<MessageHandler> json = messageHandlers.get(channel);
+    Set<BinaryMessageHandler> binary = binaryHandlers.get(channel);
+    return (json != null && !json.isEmpty()) || (binary != null && !binary.isEmpty());
+  }
+
+  private void unsubscribeIfUnused(String channel) {
+    if (!hasHandlers(channel)) send(Protocol.unsubscribe(channel));
+  }
+
+  private void send(String text) {
+    WebSocket socket = webSocket;
+    if (socket != null && connected) socket.sendText(text, true);
+  }
+
+  private void startHeartbeat() {
+    stopHeartbeat();
+    heartbeatTask = scheduler.scheduleAtFixedRate(
+        () -> send(Protocol.heartbeat()), 30, 30, TimeUnit.SECONDS);
+  }
+
+  private void stopHeartbeat() {
+    cancel(heartbeatTask);
+    heartbeatTask = null;
+  }
+
+  private void dispatch(Runnable callback) {
+    if (parent == null) callback.run();
+    else callbackQueue.add(callback);
+  }
+
+  private void notifyConnected() {
+    Runnable handler = connectHandler;
+    if (handler != null) handler.run();
+  }
+
+  private void notifyDisconnected() {
+    Runnable handler = disconnectHandler;
+    if (handler != null) handler.run();
+  }
+
+  private void notifyError(DataNetError error) {
+    ErrorHandler handler = errorHandler;
+    if (handler != null) handler.onError(error);
+    else System.err.println(error.getMessage());
+  }
+
+  private static void cancel(ScheduledFuture<?> task) {
+    if (task != null) task.cancel(false);
+  }
+
+  private static String encode(String value) {
+    return URLEncoder.encode(value, StandardCharsets.UTF_8);
+  }
+
+  private static String projectIdFromJwt(String token) {
+    try {
+      String[] parts = token.split("\\.");
+      if (parts.length < 2) return null;
+      byte[] decoded = Base64.getUrlDecoder().decode(parts[1]);
+      return JSONObject.parse(new String(decoded, StandardCharsets.UTF_8)).getString("pid", null);
+    } catch (RuntimeException ignored) {
+      return null;
+    }
+  }
+
+  private static Throwable unwrap(Throwable failure) {
+    return failure.getCause() == null ? failure : failure.getCause();
+  }
+
+  private static DataNetError asDataNetError(Throwable failure, String fallbackCode) {
+    Throwable cause = unwrap(failure);
+    if (cause instanceof DataNetError error) return error;
+    return new DataNetError(fallbackCode, "DataNet: " + cause.getMessage(), cause);
+  }
+
+  private final class SocketListener implements WebSocket.Listener {
+    private final long generation;
+    private final StringBuilder textBuffer = new StringBuilder();
+
+    private SocketListener(long generation) {
+      this.generation = generation;
+    }
+
+    @Override
+    public void onOpen(WebSocket socket) {
+      if (generation != activeGeneration || explicitlyDisconnected) {
+        socket.abort();
+        return;
+      }
+      webSocket = socket;
+      socket.request(1);
+    }
+
+    @Override
+    public CompletionStage<?> onText(WebSocket socket, CharSequence data, boolean last) {
+      synchronized (textBuffer) {
+        textBuffer.append(data);
+        if (last) {
+          String complete = textBuffer.toString();
+          textBuffer.setLength(0);
+          handleText(generation, complete);
+        }
+      }
+      socket.request(1);
+      return null;
+    }
+
+    @Override
+    public CompletionStage<?> onBinary(WebSocket socket, ByteBuffer data, boolean last) {
+      socket.request(1);
+      return null;
+    }
+
+    @Override
+    public CompletionStage<?> onClose(WebSocket socket, int statusCode, String reason) {
+      handleSocketEnded(generation,
+          explicitlyDisconnected ? null : new DataNetError("connection_closed",
+              "DataNet: connection closed (" + statusCode + (reason.isBlank() ? "" : " " + reason) + ")"));
+      return null;
+    }
+
+    @Override
+    public void onError(WebSocket socket, Throwable failure) {
+      handleSocketEnded(generation,
+          new DataNetError("connection_error", "DataNet: WebSocket error", failure));
+    }
+  }
+}
diff --git a/src/main/java/art/datanet/DataNetConfig.java b/src/main/java/art/datanet/DataNetConfig.java
new file mode 100644
index 0000000..b0b5d92
--- /dev/null
+++ b/src/main/java/art/datanet/DataNetConfig.java
@@ -0,0 +1,106 @@
+package art.datanet;
+
+import java.net.URI;
+import java.time.Duration;
+import java.util.Objects;
+
+/** Connection settings for a {@link DataNet} client. */
+public final class DataNetConfig {
+  static final URI DEFAULT_API_URL = URI.create("https://api.datanet.art");
+  static final URI DEFAULT_WS_URL = URI.create("wss://ws.datanet.art/ws");
+
+  final String apiKey;
+  final String deviceId;
+  final String clientId;
+  final String displayName;
+  final URI apiUrl;
+  final URI wsUrl;
+  final int maxReconnectAttempts;
+  final Duration requestTimeout;
+
+  private DataNetConfig(Builder builder) {
+    this.apiKey = requireText(builder.apiKey, "apiKey");
+    this.deviceId = trimToNull(builder.deviceId);
+    this.clientId = trimToNull(builder.clientId);
+    this.displayName = trimToNull(builder.displayName);
+    this.apiUrl = Objects.requireNonNull(builder.apiUrl, "apiUrl");
+    this.wsUrl = Objects.requireNonNull(builder.wsUrl, "wsUrl");
+    if (builder.maxReconnectAttempts < 0) {
+      throw new IllegalArgumentException("maxReconnectAttempts must be at least 0");
+    }
+    this.maxReconnectAttempts = builder.maxReconnectAttempts;
+    this.requestTimeout = Objects.requireNonNull(builder.requestTimeout, "requestTimeout");
+  }
+
+  /** Start configuring a client with a DataNet project API key. */
+  public static Builder builder(String apiKey) {
+    return new Builder(apiKey);
+  }
+
+  /** Fluent builder for optional device identity and endpoint settings. */
+  public static final class Builder {
+    private final String apiKey;
+    private String deviceId;
+    private String clientId = "processing";
+    private String displayName = "DataNet's Processing Sketch";
+    private URI apiUrl = DEFAULT_API_URL;
+    private URI wsUrl = DEFAULT_WS_URL;
+    private int maxReconnectAttempts = 5;
+    private Duration requestTimeout = Duration.ofSeconds(10);
+
+    private Builder(String apiKey) {
+      this.apiKey = apiKey;
+    }
+
+    public Builder deviceId(String value) {
+      this.deviceId = value;
+      return this;
+    }
+
+    public Builder clientId(String value) {
+      this.clientId = value;
+      return this;
+    }
+
+    /** Set the human-readable device name shown in DataNet dashboards. */
+    public Builder displayName(String value) {
+      this.displayName = value;
+      return this;
+    }
+
+    public Builder apiUrl(String value) {
+      this.apiUrl = URI.create(requireText(value, "apiUrl"));
+      return this;
+    }
+
+    public Builder webSocketUrl(String value) {
+      this.wsUrl = URI.create(requireText(value, "webSocketUrl"));
+      return this;
+    }
+
+    public Builder maxReconnectAttempts(int value) {
+      this.maxReconnectAttempts = value;
+      return this;
+    }
+
+    public Builder requestTimeout(Duration value) {
+      this.requestTimeout = value;
+      return this;
+    }
+
+    public DataNetConfig build() {
+      return new DataNetConfig(this);
+    }
+  }
+
+  private static String requireText(String value, String name) {
+    if (value == null || value.trim().isEmpty()) {
+      throw new IllegalArgumentException(name + " must not be blank");
+    }
+    return value.trim();
+  }
+
+  private static String trimToNull(String value) {
+    return value == null || value.trim().isEmpty() ? null : value.trim();
+  }
+}
diff --git a/src/main/java/art/datanet/DataNetError.java b/src/main/java/art/datanet/DataNetError.java
new file mode 100644
index 0000000..889a547
--- /dev/null
+++ b/src/main/java/art/datanet/DataNetError.java
@@ -0,0 +1,38 @@
+package art.datanet;
+
+/** A structured error returned by DataNet or raised by the client. */
+public final class DataNetError extends RuntimeException {
+  private static final long serialVersionUID = 1L;
+  private final String code;
+  private final String channel;
+  private final Long retryMs;
+  private final String scope;
+  private final Integer status;
+  private final Integer limit;
+
+  DataNetError(String code, String message) {
+    this(code, message, null, null, null, null, null, null);
+  }
+
+  DataNetError(String code, String message, Throwable cause) {
+    this(code, message, null, null, null, null, null, cause);
+  }
+
+  DataNetError(String code, String message, String channel, Long retryMs,
+      String scope, Integer status, Integer limit, Throwable cause) {
+    super(message, cause);
+    this.code = code;
+    this.channel = channel;
+    this.retryMs = retryMs;
+    this.scope = scope;
+    this.status = status;
+    this.limit = limit;
+  }
+
+  public String code() { return code; }
+  public String channel() { return channel; }
+  public Long retryMs() { return retryMs; }
+  public String scope() { return scope; }
+  public Integer status() { return status; }
+  public Integer limit() { return limit; }
+}
diff --git a/src/main/java/art/datanet/ErrorHandler.java b/src/main/java/art/datanet/ErrorHandler.java
new file mode 100644
index 0000000..77492d0
--- /dev/null
+++ b/src/main/java/art/datanet/ErrorHandler.java
@@ -0,0 +1,7 @@
+package art.datanet;
+
+/** Receives structured connection, protocol, and API errors. */
+@FunctionalInterface
+public interface ErrorHandler {
+  void onError(DataNetError error);
+}
diff --git a/src/main/java/art/datanet/MessageHandler.java b/src/main/java/art/datanet/MessageHandler.java
new file mode 100644
index 0000000..84cb6d4
--- /dev/null
+++ b/src/main/java/art/datanet/MessageHandler.java
@@ -0,0 +1,7 @@
+package art.datanet;
+
+/** Receives a JSON-compatible value and its message metadata. */
+@FunctionalInterface
+public interface MessageHandler {
+  void onMessage(Object data, MessageMeta meta);
+}
diff --git a/src/main/java/art/datanet/MessageMeta.java b/src/main/java/art/datanet/MessageMeta.java
new file mode 100644
index 0000000..356819e
--- /dev/null
+++ b/src/main/java/art/datanet/MessageMeta.java
@@ -0,0 +1,4 @@
+package art.datanet;
+
+/** Sender and timing information accompanying a JSON message. */
+public record MessageMeta(String channel, String from, long timestamp) {}
diff --git a/src/main/java/art/datanet/PresenceHandler.java b/src/main/java/art/datanet/PresenceHandler.java
new file mode 100644
index 0000000..a2cadb2
--- /dev/null
+++ b/src/main/java/art/datanet/PresenceHandler.java
@@ -0,0 +1,7 @@
+package art.datanet;
+
+/** Receives a presence lookup result on the Processing animation thread. */
+@FunctionalInterface
+public interface PresenceHandler {
+  void onPresence(PresenceResult presence);
+}
diff --git a/src/main/java/art/datanet/PresenceResult.java b/src/main/java/art/datanet/PresenceResult.java
new file mode 100644
index 0000000..ddb684a
--- /dev/null
+++ b/src/main/java/art/datanet/PresenceResult.java
@@ -0,0 +1,10 @@
+package art.datanet;
+
+import java.util.List;
+
+/** Current authoritative occupancy for one DataNet channel. */
+public record PresenceResult(int occupancy, List<String> members) {
+  public PresenceResult {
+    members = List.copyOf(members);
+  }
+}
diff --git a/src/main/java/art/datanet/Protocol.java b/src/main/java/art/datanet/Protocol.java
new file mode 100644
index 0000000..a145c67
--- /dev/null
+++ b/src/main/java/art/datanet/Protocol.java
@@ -0,0 +1,75 @@
+package art.datanet;
+
+import java.util.Base64;
+import processing.data.JSONObject;
+
+final class Protocol {
+  private Protocol() {}
+
+  static String subscribe(String channel) {
+    return new JSONObject().setString("op", "sub").setString("ch", channel).toString();
+  }
+
+  static String unsubscribe(String channel) {
+    return new JSONObject().setString("op", "unsub").setString("ch", channel).toString();
+  }
+
+  static String publish(String channel, Object data) {
+    return new JSONObject().setString("op", "pub").setString("ch", channel).put("d", data).toString();
+  }
+
+  static String publishBinary(String channel, byte[] data, String contentType, JSONObject metadata) {
+    JSONObject envelope = new JSONObject()
+        .setString("op", "pub")
+        .setString("ch", channel)
+        .setBoolean("bin", true)
+        .setString("b64", Base64.getEncoder().encodeToString(data))
+        .setString("ct", contentType);
+    if (metadata != null) envelope.setJSONObject("meta", metadata);
+    return envelope.toString();
+  }
+
+  static String heartbeat() {
+    return new JSONObject().setString("op", "hb").toString();
+  }
+
+  static byte[] decodeBinary(String encoded) {
+    return Base64.getDecoder().decode(encoded);
+  }
+
+  static DataNetError gatewayError(JSONObject message) {
+    String code = message.getString("code", message.getString("error", "gateway_error"));
+    String channel = message.getString("channel", message.getString("ch", null));
+    Long retryMs = numberAsLong(message, "retry_ms");
+    String scope = message.getString("scope", null);
+    Integer limit = numberAsInteger(message, "limit");
+    return new DataNetError(
+        code,
+        "DataNet: " + message.getString("error", code) + (channel == null ? "" : " (" + channel + ")"),
+        channel,
+        retryMs,
+        scope,
+        null,
+        limit,
+        null);
+  }
+
+  static String requireChannel(String channel) {
+    if (channel == null || channel.trim().isEmpty()) {
+      throw new IllegalArgumentException("channel must not be blank");
+    }
+    return channel.trim();
+  }
+
+  private static Long numberAsLong(JSONObject object, String key) {
+    if (!object.hasKey(key) || object.isNull(key)) return null;
+    Object value = object.get(key);
+    return value instanceof Number number ? number.longValue() : null;
+  }
+
+  private static Integer numberAsInteger(JSONObject object, String key) {
+    if (!object.hasKey(key) || object.isNull(key)) return null;
+    Object value = object.get(key);
+    return value instanceof Number number ? number.intValue() : null;
+  }
+}
diff --git a/src/main/java/art/datanet/package-info.java b/src/main/java/art/datanet/package-info.java
new file mode 100644
index 0000000..0968ae9
--- /dev/null
+++ b/src/main/java/art/datanet/package-info.java
@@ -0,0 +1,2 @@
+/** Realtime DataNet pub/sub client types for Processing 4 sketches. */
+package art.datanet;
diff --git a/src/test/java/art/datanet/DataNetConfigTest.java b/src/test/java/art/datanet/DataNetConfigTest.java
new file mode 100644
index 0000000..99f55d0
--- /dev/null
+++ b/src/test/java/art/datanet/DataNetConfigTest.java
@@ -0,0 +1,35 @@
+package art.datanet;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+
+final class DataNetConfigTest {
+  @Test
+  void suppliesProcessingFriendlyDefaults() {
+    DataNetConfig config = DataNetConfig.builder("ak_test").build();
+
+    assertEquals("processing", config.clientId);
+    assertEquals("DataNet's Processing Sketch", config.displayName);
+    assertEquals(5, config.maxReconnectAttempts);
+  }
+
+  @Test
+  void supportsCustomDeviceIdentity() {
+    DataNetConfig config = DataNetConfig.builder("ak_test")
+        .deviceId("gallery-screen-1")
+        .displayName("DataNet's Gallery Screen")
+        .build();
+
+    assertEquals("gallery-screen-1", config.deviceId);
+    assertEquals("DataNet's Gallery Screen", config.displayName);
+  }
+
+  @Test
+  void rejectsMissingApiKeyAndNegativeReconnects() {
+    assertThrows(IllegalArgumentException.class, () -> DataNetConfig.builder(" ").build());
+    assertThrows(IllegalArgumentException.class,
+        () -> DataNetConfig.builder("ak_test").maxReconnectAttempts(-1).build());
+  }
+}
diff --git a/src/test/java/art/datanet/ProtocolTest.java b/src/test/java/art/datanet/ProtocolTest.java
new file mode 100644
index 0000000..6c9724f
--- /dev/null
+++ b/src/test/java/art/datanet/ProtocolTest.java
@@ -0,0 +1,67 @@
+package art.datanet;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.Test;
+import processing.data.JSONObject;
+
+final class ProtocolTest {
+  @Test
+  void buildsJsonPublishEnvelope() {
+    JSONObject data = new JSONObject().setInt("value", 42);
+    JSONObject envelope = JSONObject.parse(Protocol.publish("project.demo.sensor", data));
+
+    assertEquals("pub", envelope.getString("op"));
+    assertEquals("project.demo.sensor", envelope.getString("ch"));
+    assertEquals(42, envelope.getJSONObject("d").getInt("value"));
+  }
+
+  @Test
+  void roundTripsBinaryEnvelopeAndMetadata() {
+    byte[] payload = new byte[] {0, 1, (byte) 255};
+    JSONObject metadata = new JSONObject().setInt("universe", 1);
+    JSONObject envelope = JSONObject.parse(
+        Protocol.publishBinary("project.demo.lights", payload, "binary/dmx", metadata));
+
+    assertTrue(envelope.getBoolean("bin"));
+    assertEquals("binary/dmx", envelope.getString("ct"));
+    assertEquals(1, envelope.getJSONObject("meta").getInt("universe"));
+    assertArrayEquals(payload, Protocol.decodeBinary(envelope.getString("b64")));
+  }
+
+  @Test
+  void omitsMetadataWhenItWasNotProvided() {
+    JSONObject envelope = JSONObject.parse(
+        Protocol.publishBinary("project.demo.bytes", new byte[] {1}, "application/octet-stream", null));
+
+    assertFalse(envelope.hasKey("meta"));
+  }
+
+  @Test
+  void convertsGatewayErrorsToStructuredErrors() {
+    JSONObject envelope = new JSONObject()
+        .setString("type", "error")
+        .setString("error", "rate_limited")
+        .setString("channel", "project.demo.sensor")
+        .setLong("retry_ms", 2500)
+        .setString("scope", "connection")
+        .setInt("limit", 20);
+
+    DataNetError error = Protocol.gatewayError(envelope);
+
+    assertEquals("rate_limited", error.code());
+    assertEquals("project.demo.sensor", error.channel());
+    assertEquals(2500L, error.retryMs());
+    assertEquals("connection", error.scope());
+    assertEquals(20, error.limit());
+  }
+
+  @Test
+  void rejectsBlankChannels() {
+    assertThrows(IllegalArgumentException.class, () -> Protocol.requireChannel("  "));
+  }
+}