[WIP] try RxJava

server-api/build.gradle

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+ext {
+    netty_version = '4.1.22.Final';
+
+    library = [
+            rxjava: ['io.reactivex.rxjava3:rxjava:3.0.3'],
+            netty: [
+                    "io.netty:netty-transport:$netty_version"
+            ]
+    ]
+}
+
+dependencies {
+    /* COMPONENTS */
+    compile project(':protocol')
+    compile library.rxjava
+
+    implementation library.netty
+}

server-api/src/main/java/mc/server/reactive/NetworkContainer.java

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+package mc.server.reactive;
+
+import io.netty.channel.Channel;
+import lombok.Data;
+import mc.protocol.Packet;
+
+@Data
+public class NetworkContainer<T extends Packet> {
+
+    private final Channel channel;
+    private final T packet;
+}

server-api/src/main/java/mc/server/reactive/RxProvider.java

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+package mc.server.reactive;
+
+import io.reactivex.rxjava3.core.Observable;
+import io.reactivex.rxjava3.core.Observer;
+import io.reactivex.rxjava3.subjects.PublishSubject;
+import io.reactivex.rxjava3.subjects.Subject;
+import mc.protocol.Packet;
+
+import java.util.HashMap;
+import java.util.Map;
+
+@SuppressWarnings({ "rawtypes", "unchecked" })
+public class RxProvider {
+
+    private final Map<Class, Subject> subjectMap = new HashMap<>();
+
+    public <T extends Packet> Observable<NetworkContainer<T>> getPacketObservable(Class<T> packetType) {
+        return giveSubject(packetType);
+    }
+
+    public Observer<NetworkContainer<? extends Packet>> getPacketObserver(Class<? extends Packet> packetType) {
+        return giveSubject(packetType);
+    }
+
+    private Subject giveSubject(Class<? extends Packet> packetType) {
+        return subjectMap.computeIfAbsent(packetType, key -> PublishSubject.create());
+    }
+}