From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: granny <contact@granny.dev>
Date: Mon, 23 Mar 2026 17:48:11 -0700
Subject: [PATCH] Alternative Keepalive Handling for Improved Keepalive Ping
 System


diff --git a/net/minecraft/server/network/ServerCommonPacketListenerImpl.java b/net/minecraft/server/network/ServerCommonPacketListenerImpl.java
index b8a4b4cc02a2fc6b70f4b840796eed501aad6239..02c6733ce1de543dab3bf558148879039e501257 100644
--- a/net/minecraft/server/network/ServerCommonPacketListenerImpl.java
+++ b/net/minecraft/server/network/ServerCommonPacketListenerImpl.java
@@ -40,10 +40,11 @@ public abstract class ServerCommonPacketListenerImpl implements ServerCommonPack
     public final Connection connection; // Paper
     private final boolean transferred;
     //private long keepAliveTime; // Paper - improve keepalives
-    //private boolean keepAlivePending; // Paper - improve keepalives
+    private boolean keepAlivePending; // Paper - improve keepalives // Purpur - Alternative Keepalive Handling
     //private long keepAliveChallenge; // Paper - improve keepalives
     private long closedListenerTime;
     private boolean closed = false;
+    private it.unimi.dsi.fastutil.longs.LongList keepAlives = new it.unimi.dsi.fastutil.longs.LongArrayList(); // Purpur - Alternative Keepalive Handling
     private volatile int latency; // Paper - improve keepalives - make volatile
     private final io.papermc.paper.util.KeepAlive keepAlive; // Paper - improve keepalives
     private volatile boolean suspendFlushingOnServerThread = false;
@@ -105,6 +110,18 @@ public abstract class ServerCommonPacketListenerImpl implements ServerCommonPack
         // Paper start - improve keepalives
         long now = System.nanoTime();
         io.papermc.paper.util.KeepAlive.PendingKeepAlive pending = this.keepAlive.pendingKeepAlives.peek();
+        // Purpur start - Alternative Keepalive Handling
+        if (org.purpurmc.purpur.PurpurConfig.useAlternateKeepAlive) {
+            if (this.keepAlivePending && !keepAlives.isEmpty() && keepAlives.contains(packet.getId())) {
+                int ping = (int) (Util.getMillis() - packet.getId());
+                int updatedLatency = (this.latency * 3 + ping) / 4;
+                this.latency = updatedLatency;
+                this.keepAlivePending = false;
+                keepAlives.clear(); // we got a valid response, lets roll with it and forget the rest
+            }
+            return;
+        } else
+        // Purpur end - Alternative Keepalive Handling
         if (pending != null && pending.challengeId() == packet.getId()) {
             this.keepAlive.pendingKeepAlives.remove(pending);
 
@@ -264,6 +287,23 @@ public abstract class ServerCommonPacketListenerImpl implements ServerCommonPack
         Profiler.get().push("keepAlive");
         long millis = Util.getMillis();
         // Paper start - improve keepalives
+        // Purpur start - Alternative Keepalive Handling
+        if (org.purpurmc.purpur.PurpurConfig.useAlternateKeepAlive) {
+            if (this.checkIfClosed(millis) && !this.processedDisconnect) {
+                long currTime = System.nanoTime();
+                if ((currTime - this.keepAlive.lastKeepAliveTx) >= java.util.concurrent.TimeUnit.SECONDS.toNanos(1L)) { // 1 second
+                    this.keepAlive.lastKeepAliveTx = currTime;
+                    if (this.keepAlivePending && !this.processedDisconnect && keepAlives.size() * 1000L >= KEEPALIVE_LIMIT) {
+                        this.disconnect(TIMEOUT_DISCONNECTION_MESSAGE, io.papermc.paper.connection.DisconnectionReason.TIMEOUT);
+                    } else if (this.checkIfClosed(millis)) {
+                        this.keepAlivePending = true;
+                        this.keepAlives.add(millis); // currentTime is ID
+                        this.send(new ClientboundKeepAlivePacket(millis));
+                    }
+                }
+            }
+        } else
+        // Purpur end - Alternative Keepalive Handling
         if (this.checkIfClosed(millis) && !this.processedDisconnect) {
             long currTime = System.nanoTime();