Direct connections with peers now prefer those with the highest number of chunks for a resource. Once a connection has been attempted with a peer, remove it from the list so that it isn't attempted again in the same round.

src/main/java/org/qortal/controller/arbitrary/ArbitraryDataFileManager.java

@@ -293,6 +293,10 @@ public class ArbitraryDataFileManager extends Thread {
         }
     }
 
+    private void removeDirectConnectionInfo(ArbitraryDirectConnectionInfo connectionInfo) {
+        this.directConnectionInfo.remove(connectionInfo);
+    }
+
     public boolean fetchDataFilesFromPeersForSignature(byte[] signature) {
         String signature58 = Base58.encode(signature);
 
@@ -305,9 +309,19 @@ public class ArbitraryDataFileManager extends Thread {
 
         LOGGER.debug("Attempting a direct peer connection for signature {}...", signature58);
 
-        // Peers found, so pick a random one and request data from it
-        int index = new SecureRandom().nextInt(connectionInfoList.size());
-        ArbitraryDirectConnectionInfo directConnectionInfo = connectionInfoList.get(index);
+        // Peers found, so pick one with the highest number of chunks
+        Comparator<ArbitraryDirectConnectionInfo> highestChunkCountFirstComparator =
+                Comparator.comparingInt(ArbitraryDirectConnectionInfo::getHashCount).reversed();
+        ArbitraryDirectConnectionInfo directConnectionInfo = connectionInfoList.stream()
+                .sorted(highestChunkCountFirstComparator).findFirst().orElse(null);
+
+        if (directConnectionInfo == null) {
+            return false;
+        }
+
+        // Remove from the list so that a different peer is tried next time
+        removeDirectConnectionInfo(directConnectionInfo);
+
         String peerAddressString = directConnectionInfo.getPeerAddress();
         boolean success = Network.getInstance().requestDataFromPeer(peerAddressString, signature);
 

src/main/java/org/qortal/data/arbitrary/ArbitraryDirectConnectionInfo.java

@@ -1,6 +1,8 @@
 package org.qortal.data.arbitrary;
 
+import java.util.Arrays;
 import java.util.List;
+import java.util.Objects;
 
 public class ArbitraryDirectConnectionInfo {
 
@@ -31,4 +33,27 @@ public class ArbitraryDirectConnectionInfo {
     public long getTimestamp() {
         return this.timestamp;
     }
+
+    public int getHashCount() {
+        if (this.hashes == null) {
+            return 0;
+        }
+        return this.hashes.size();
+    }
+
+    @Override
+    public boolean equals(Object other) {
+        if (other == this)
+            return true;
+
+        if (!(other instanceof ArbitraryDirectConnectionInfo))
+            return false;
+
+        ArbitraryDirectConnectionInfo otherDirectConnectionInfo = (ArbitraryDirectConnectionInfo) other;
+
+        return Arrays.equals(this.signature, otherDirectConnectionInfo.getSignature())
+                && Objects.equals(this.peerAddress, otherDirectConnectionInfo.getPeerAddress())
+                && Objects.equals(this.hashes, otherDirectConnectionInfo.getHashes())
+                && Objects.equals(this.timestamp, otherDirectConnectionInfo.getTimestamp());
+    }
 }