Merge branch 'master' into sync-multiple-blocks

# Conflicts:
#	src/main/java/org/qortal/settings/Settings.java

.gitignore

@@ -1,6 +1,7 @@
 /db*
 /bin/
 /target/
+/qortal-backup/
 /log.txt.*
 /arbitrary*
 /Qortal-BTC*
@@ -20,7 +21,7 @@
 /qortal.iml
 .DS_Store
 /src/main/resources/resources
-/src/main/resources/log*.properties
 /*.jar
 /run.pid
 /run.log
+/WindowsInstaller/Install Files/qortal.jar

WindowsInstaller/Qortal.aip

@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
 <DOCUMENT Type="Advanced Installer" CreateVersion="14.9" version="18.2" Modules="enterprise" RootPath="." Language="en_GB" Id="{713E21E0-28FC-422F-8A95-823D01A5F80B}">
   <COMPONENT cid="caphyon.advinst.msicomp.MsiPropsComponent">
     <ROW Property="AI_BITMAP_DISPLAY_MODE" Value="0"/>
@@ -17,10 +17,10 @@
     <ROW Property="Manufacturer" Value="Qortal"/>
     <ROW Property="MsiLogging" MultiBuildValue="DefaultBuild:vp"/>
     <ROW Property="NTP_GOOD" Value="false"/>
-    <ROW Property="ProductCode" Value="1033:{75ABAC87-9F88-4229-A7D5-DE07F082566D} 1049:{42997A88-BD5D-4829-9FFD-96D0F14A2572} 2052:{0F6AAF5B-3089-4837-AC63-DEEC282862D9} 2057:{F3CAA239-F0FC-456F-B3F8-D5D846030731} " Type="16"/>
+    <ROW Property="ProductCode" Value="1033:{EB5562C3-664E-4A8B-8907-6D2033B98836} 1049:{36D0E774-B970-4A13-BCC4-1BA6AB3B2633} 2052:{AF6B6B44-9404-403A-B00F-B7110C28E453} 2057:{68BB9EB8-5991-42E5-841C-E76ACE51166D} " Type="16"/>
     <ROW Property="ProductLanguage" Value="2057"/>
     <ROW Property="ProductName" Value="Qortal"/>
-    <ROW Property="ProductVersion" Value="1.5.2" Type="32"/>
+    <ROW Property="ProductVersion" Value="1.5.4" Type="32"/>
     <ROW Property="RECONFIG_NTP" Value="true"/>
     <ROW Property="REMOVE_BLOCKCHAIN" Value="YES" Type="4"/>
     <ROW Property="REPAIR_BLOCKCHAIN" Value="YES" Type="4"/>
@@ -212,7 +212,7 @@
     <ROW Component="ADDITIONAL_LICENSE_INFO_71" ComponentId="{12A3ADBE-BB7A-496C-8869-410681E6232F}" Directory_="jdk.zipfs_Dir" Attributes="0" KeyPath="ADDITIONAL_LICENSE_INFO_71" Type="0"/>
     <ROW Component="ADDITIONAL_LICENSE_INFO_8" ComponentId="{D53AD95E-CF96-4999-80FC-5812277A7456}" Directory_="java.naming_Dir" Attributes="0" KeyPath="ADDITIONAL_LICENSE_INFO_8" Type="0"/>
     <ROW Component="ADDITIONAL_LICENSE_INFO_9" ComponentId="{6B7EA9B0-5D17-47A8-B78C-FACE86D15E01}" Directory_="java.net.http_Dir" Attributes="0" KeyPath="ADDITIONAL_LICENSE_INFO_9" Type="0"/>
-    <ROW Component="AI_CustomARPName" ComponentId="{922F3242-D791-484E-B034-2EC3EBE7E57F}" Directory_="APPDIR" Attributes="260" KeyPath="DisplayName" Options="1"/>
+    <ROW Component="AI_CustomARPName" ComponentId="{83DFE721-3F68-4ABE-8697-8EC3A91EEB8A}" Directory_="APPDIR" Attributes="260" KeyPath="DisplayName" Options="1"/>
     <ROW Component="AI_ExePath" ComponentId="{3644948D-AE0B-41BB-9FAF-A79E70490A08}" Directory_="APPDIR" Attributes="260" KeyPath="AI_ExePath"/>
     <ROW Component="APPDIR" ComponentId="{680DFDDE-3FB4-47A5-8FF5-934F576C6F91}" Directory_="APPDIR" Attributes="0"/>
     <ROW Component="AccessBridgeCallbacks.h" ComponentId="{288055D1-1062-47A3-AA44-5601B4E38AED}" Directory_="bridge_Dir" Attributes="0" KeyPath="AccessBridgeCallbacks.h" Type="0"/>

WindowsInstaller/README.md

@@ -12,7 +12,7 @@ configured paths, or create a dummy `D:` drive with the expected layout.
 
 Typical build procedure:
 
-* Overwrite the `qortal.jar` file in `Install-Files\`
+* Place the `qortal.jar` file in `Install-Files\`
 * Open AdvancedInstaller with qortal.aip file
 * If releasing a new version, change version number in:
 	+ "Product Information" side menu

pom.xml

@@ -3,7 +3,7 @@
 	<modelVersion>4.0.0</modelVersion>
 	<groupId>org.qortal</groupId>
 	<artifactId>qortal</artifactId>
-	<version>1.5.3</version>
+	<version>1.5.4</version>
 	<packaging>jar</packaging>
 	<properties>
 		<skipTests>true</skipTests>

src/main/java/org/qortal/api/websocket/ChatMessagesWebSocket.java

@@ -115,6 +115,9 @@ public class ChatMessagesWebSocket extends ApiWebSocket {
 	}
 
 	private void onNotify(Session session, ChatTransactionData chatTransactionData, List<String> involvingAddresses) {
+		if (chatTransactionData == null)
+			return;
+
 		// We only want direct/non-group messages where sender/recipient match our addresses
 		String recipient = chatTransactionData.getRecipient();
 		if (recipient == null)

src/main/java/org/qortal/block/Block.java

@@ -476,6 +476,16 @@ public class Block {
 		return this.minter;
 	}
 
+
+	public void setRepository(Repository repository) throws DataException {
+		this.repository = repository;
+
+		for (Transaction transaction : this.getTransactions()) {
+			transaction.setRepository(repository);
+		}
+	}
+
+
 	// More information
 
 	/**
@@ -524,8 +534,10 @@ public class Block {
 		long nonAtTransactionCount = transactionsData.stream().filter(transactionData -> transactionData.getType() != TransactionType.AT).count();
 
 		// The number of non-AT transactions fetched from repository should correspond with Block's transactionCount
-		if (nonAtTransactionCount != this.blockData.getTransactionCount())
+		if (nonAtTransactionCount != this.blockData.getTransactionCount()) {
+			LOGGER.error(() -> String.format("Block's transactions from repository (%d) do not match block's transaction count (%d)", nonAtTransactionCount, this.blockData.getTransactionCount()));
 			throw new IllegalStateException("Block's transactions from repository do not match block's transaction count");
+		}
 
 		this.transactions = new ArrayList<>();
 

src/main/java/org/qortal/controller/Controller.java

@@ -68,9 +68,11 @@ import org.qortal.network.Network;
 import org.qortal.network.Peer;
 import org.qortal.network.message.ArbitraryDataMessage;
 import org.qortal.network.message.BlockSummariesMessage;
+import org.qortal.network.message.BlocksMessage;
 import org.qortal.network.message.CachedBlockMessage;
 import org.qortal.network.message.GetArbitraryDataMessage;
 import org.qortal.network.message.GetBlockMessage;
+import org.qortal.network.message.GetBlocksMessage;
 import org.qortal.network.message.GetBlockSummariesMessage;
 import org.qortal.network.message.GetOnlineAccountsMessage;
 import org.qortal.network.message.GetPeersMessage;
@@ -101,6 +103,8 @@ import org.qortal.utils.Triple;
 
 import com.google.common.primitives.Longs;
 
+import static org.qortal.network.Peer.FETCH_BLOCKS_TIMEOUT;
+
 public class Controller extends Thread {
 
 	static {
@@ -222,6 +226,18 @@ public class Controller extends Thread {
 		}
 		public GetBlockMessageStats getBlockMessageStats = new GetBlockMessageStats();
 
+		public static class GetBlocksMessageStats {
+			public AtomicLong requests = new AtomicLong();
+			public AtomicLong cacheHits = new AtomicLong();
+			public AtomicLong unknownBlocks = new AtomicLong();
+			public AtomicLong cacheFills = new AtomicLong();
+			public AtomicLong fullyFromCache = new AtomicLong();
+
+			public GetBlocksMessageStats() {
+			}
+		}
+		public GetBlocksMessageStats getBlocksMessageStats = new GetBlocksMessageStats();
+
 		public static class GetBlockSummariesStats {
 			public AtomicLong requests = new AtomicLong();
 			public AtomicLong cacheHits = new AtomicLong();
@@ -259,17 +275,29 @@ public class Controller extends Thread {
 			throw new RuntimeException("Can't read build.properties resource", e);
 		}
 
+		// Determine build timestamp
 		String buildTimestampProperty = properties.getProperty("build.timestamp");
-		if (buildTimestampProperty == null)
+		if (buildTimestampProperty == null) {
 			throw new RuntimeException("Can't read build.timestamp from build.properties resource");
-
-		this.buildTimestamp = LocalDateTime.parse(buildTimestampProperty, DateTimeFormatter.ofPattern("yyyyMMddHHmmss")).toEpochSecond(ZoneOffset.UTC);
+		}
+		if (buildTimestampProperty.startsWith("$")) {
+			// Maven vars haven't been replaced - this was most likely built using an IDE, not via mvn package
+			this.buildTimestamp = System.currentTimeMillis();
+			buildTimestampProperty = "unknown";
+		} else {
+			this.buildTimestamp = LocalDateTime.parse(buildTimestampProperty, DateTimeFormatter.ofPattern("yyyyMMddHHmmss")).toEpochSecond(ZoneOffset.UTC);
+		}
 		LOGGER.info(String.format("Build timestamp: %s", buildTimestampProperty));
 
+		// Determine build version
 		String buildVersionProperty = properties.getProperty("build.version");
-		if (buildVersionProperty == null)
+		if (buildVersionProperty == null) {
 			throw new RuntimeException("Can't read build.version from build.properties resource");
-
+		}
+		if (buildVersionProperty.contains("${git.commit.id.abbrev}")) {
+			// Maven vars haven't been replaced - this was most likely built using an IDE, not via mvn package
+			buildVersionProperty = buildVersionProperty.replace("${git.commit.id.abbrev}", "debug");
+		}
 		this.buildVersion = VERSION_PREFIX + buildVersionProperty;
 		LOGGER.info(String.format("Build version: %s", this.buildVersion));
 
@@ -678,7 +706,7 @@ public class Controller extends Thread {
 
 		final int peersRemoved = peersBeforeComparison - peers.size();
 		if (peersRemoved > 0 && peers.size() > 0)
-			LOGGER.info(String.format("Ignoring %d peers on inferior chains. Peers remaining: %d", peersRemoved, peers.size()));
+			LOGGER.debug(String.format("Ignoring %d peers on inferior chains. Peers remaining: %d", peersRemoved, peers.size()));
 
 		if (peers.isEmpty())
 			return;
@@ -687,7 +715,7 @@ public class Controller extends Thread {
 			StringBuilder finalPeersString = new StringBuilder();
 			for (Peer peer : peers)
 				finalPeersString = finalPeersString.length() > 0 ? finalPeersString.append(", ").append(peer) : finalPeersString.append(peer);
-			LOGGER.info(String.format("Choosing random peer from: [%s]", finalPeersString.toString()));
+			LOGGER.debug(String.format("Choosing random peer from: [%s]", finalPeersString.toString()));
 		}
 
 		// Pick random peer to sync with
@@ -710,6 +738,7 @@ public class Controller extends Thread {
 				hasStatusChanged = true;
 			}
 		}
+		peer.setSyncInProgress(true);
 
 		if (hasStatusChanged)
 			updateSysTray();
@@ -789,6 +818,7 @@ public class Controller extends Thread {
 			return syncResult;
 		} finally {
 			isSynchronizing = false;
+			peer.setSyncInProgress(false);
 		}
 	}
 
@@ -883,14 +913,19 @@ public class Controller extends Thread {
 
 			List<TransactionData> transactions = repository.getTransactionRepository().getUnconfirmedTransactions();
 
+			int deletedCount = 0;
 			for (TransactionData transactionData : transactions) {
 				Transaction transaction = Transaction.fromData(repository, transactionData);
 
 				if (now >= transaction.getDeadline()) {
-					LOGGER.info(() -> String.format("Deleting expired, unconfirmed transaction %s", Base58.encode(transactionData.getSignature())));
+					LOGGER.debug(() -> String.format("Deleting expired, unconfirmed transaction %s", Base58.encode(transactionData.getSignature())));
 					repository.getTransactionRepository().delete(transactionData);
+					deletedCount++;
 				}
 			}
+			if (deletedCount > 0) {
+				LOGGER.info(String.format("Deleted %d expired, unconfirmed transaction%s", deletedCount, (deletedCount == 1 ? "" : "s")));
+			}
 
 			repository.saveChanges();
 		} catch (DataException e) {
@@ -1182,6 +1217,10 @@ public class Controller extends Thread {
 				onNetworkGetBlockMessage(peer, message);
 				break;
 
+			case GET_BLOCKS:
+				onNetworkGetBlocksMessage(peer, message);
+				break;
+
 			case TRANSACTION:
 				onNetworkTransactionMessage(peer, message);
 				break;
@@ -1296,6 +1335,54 @@ public class Controller extends Thread {
 		}
 	}
 
+	private void onNetworkGetBlocksMessage(Peer peer, Message message) {
+		GetBlocksMessage getBlocksMessage = (GetBlocksMessage) message;
+		byte[] parentSignature = getBlocksMessage.getParentSignature();
+		this.stats.getBlocksMessageStats.requests.incrementAndGet();
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+
+			// If peer's parent signature matches our latest block signature
+			// then we can short-circuit with an empty response
+			BlockData chainTip = getChainTip();
+			if (chainTip != null && Arrays.equals(parentSignature, chainTip.getSignature())) {
+				Message blocksMessage = new BlocksMessage(Collections.emptyList());
+				blocksMessage.setId(message.getId());
+				if (!peer.sendMessage(blocksMessage))
+					peer.disconnect("failed to send blocks");
+
+				return;
+			}
+
+			// Ensure that we don't serve more blocks than the amount specified in the settings
+			// Serializing multiple blocks is very slow, so by default we are using a low limit
+			int blockLimitPerRequest = Settings.getInstance().getMaxBlocksPerResponse();
+			int untrimmedBlockLimitPerRequest = Settings.getInstance().getMaxBlocksPerResponse();
+			int numberRequested = Math.min(blockLimitPerRequest, getBlocksMessage.getNumberRequested());
+
+			List<Block> blocks = new ArrayList<>();
+			BlockData blockData = repository.getBlockRepository().fromReference(parentSignature);
+
+			while (blockData != null && blocks.size() < numberRequested) {
+				// If we're dealing with untrimmed blocks, ensure we don't go above the untrimmedBlockLimitPerRequest
+				if (blockData.isTrimmed() == false && blocks.size() >= untrimmedBlockLimitPerRequest) {
+					break;
+				}
+				Block block = new Block(repository, blockData);
+				blocks.add(block);
+				blockData = repository.getBlockRepository().fromReference(blockData.getSignature());
+			}
+
+			Message blocksMessage = new BlocksMessage(blocks);
+			blocksMessage.setId(message.getId());
+			if (!peer.sendMessageWithTimeout(blocksMessage, FETCH_BLOCKS_TIMEOUT))
+				peer.disconnect("failed to send blocks");
+
+		} catch (DataException e) {
+			LOGGER.error(String.format("Repository issue while sending blocks after %s to peer %s", Base58.encode(parentSignature), peer), e);
+		}
+	}
+
 	private void onNetworkTransactionMessage(Peer peer, Message message) {
 		TransactionMessage transactionMessage = (TransactionMessage) message;
 		TransactionData transactionData = transactionMessage.getTransactionData();

src/main/java/org/qortal/controller/Synchronizer.java

@@ -25,8 +25,10 @@ import org.qortal.data.transaction.RewardShareTransactionData;
 import org.qortal.data.transaction.TransactionData;
 import org.qortal.network.Peer;
 import org.qortal.network.message.BlockMessage;
+import org.qortal.network.message.BlocksMessage;
 import org.qortal.network.message.BlockSummariesMessage;
 import org.qortal.network.message.GetBlockMessage;
+import org.qortal.network.message.GetBlocksMessage;
 import org.qortal.network.message.GetBlockSummariesMessage;
 import org.qortal.network.message.GetSignaturesV2Message;
 import org.qortal.network.message.Message;
@@ -40,12 +42,14 @@ import org.qortal.transaction.Transaction;
 import org.qortal.utils.Base58;
 import org.qortal.utils.NTP;
 
+import static org.qortal.network.Peer.FETCH_BLOCKS_TIMEOUT;
+
 public class Synchronizer {
 
 	private static final Logger LOGGER = LogManager.getLogger(Synchronizer.class);
 
 	/** Max number of new blocks we aim to add to chain tip in each sync round */
-	private static final int SYNC_BATCH_SIZE = 200; // XXX move to Settings?
+	private static final int SYNC_BATCH_SIZE = 1000; // XXX move to Settings?
 
 	/** Initial jump back of block height when searching for common block with peer */
 	private static final int INITIAL_BLOCK_STEP = 8;
@@ -58,6 +62,14 @@ public class Synchronizer {
 	/** Maximum number of block signatures we ask from peer in one go */
 	private static final int MAXIMUM_REQUEST_SIZE = 200; // XXX move to Settings?
 
+	/* Minimum peer version that supports syncing multiple blocks at once via GetBlocksMessage */
+	private static final long PEER_VERSION_160 = 0x0100060000L;
+
+
+
+
+	// Keep track of the size of the last re-org, so it can be logged
+	private int lastReorgSize;
 
 	private static Synchronizer instance;
 
@@ -139,7 +151,7 @@ public class Synchronizer {
 
 				if (wereNewRequestsMade) {
 					final long totalTimeTaken = System.currentTimeMillis() - startTime;
-					LOGGER.info(String.format("Finished searching for common blocks with %d peer%s. Found: %d. Total time taken: %d ms", peers.size(), (peers.size() != 1 ? "s" : ""), commonBlocksFound, totalTimeTaken));
+					LOGGER.debug(String.format("Finished searching for common blocks with %d peer%s. Found: %d. Total time taken: %d ms", peers.size(), (peers.size() != 1 ? "s" : ""), commonBlocksFound, totalTimeTaken));
 				}
 
 				return SynchronizationResult.OK;
@@ -506,9 +518,22 @@ public class Synchronizer {
 					byte[] peersLastBlockSignature = peerChainTipData.getLastBlockSignature();
 
 					byte[] ourLastBlockSignature = ourLatestBlockData.getSignature();
-					LOGGER.debug(String.format("Synchronizing with peer %s at height %d, sig %.8s, ts %d; our height %d, sig %.8s, ts %d", peer,
+					String syncString = String.format("Synchronizing with peer %s at height %d, sig %.8s, ts %d; our height %d, sig %.8s, ts %d", peer,
 							peerHeight, Base58.encode(peersLastBlockSignature), peer.getChainTipData().getLastBlockTimestamp(),
-							ourInitialHeight, Base58.encode(ourLastBlockSignature), ourLatestBlockData.getTimestamp()));
+							ourInitialHeight, Base58.encode(ourLastBlockSignature), ourLatestBlockData.getTimestamp());
+
+					// If our latest block is very old, we should log that we're attempting to sync with a peer
+					// Otherwise, it can appear as though nothing is happening for a while after launch
+					final Long minLatestBlockTimestamp = Controller.getMinimumLatestBlockTimestamp();
+					if (minLatestBlockTimestamp != null && ourLatestBlockData.getTimestamp() < minLatestBlockTimestamp) {
+						LOGGER.info(syncString);
+					}
+					else {
+						LOGGER.debug(syncString);
+					}
+
+					// Reset last re-org size as we are starting a new sync round
+					this.lastReorgSize = 0;
 
 					List<BlockSummaryData> peerBlockSummaries = new ArrayList<>();
 					SynchronizationResult findCommonBlockResult = fetchSummariesFromCommonBlock(repository, peer, ourInitialHeight, force, peerBlockSummaries, true);
@@ -567,10 +592,19 @@ public class Synchronizer {
 					// Commit
 					repository.saveChanges();
 
+					// Create string for logging
 					final BlockData newLatestBlockData = repository.getBlockRepository().getLastBlock();
-					LOGGER.info(String.format("Synchronized with peer %s to height %d, sig %.8s, ts: %d", peer,
+					String syncLog = String.format("Synchronized with peer %s to height %d, sig %.8s, ts: %d", peer,
 							newLatestBlockData.getHeight(), Base58.encode(newLatestBlockData.getSignature()),
-							newLatestBlockData.getTimestamp()));
+							newLatestBlockData.getTimestamp());
+
+					// Append re-org info
+					if (this.lastReorgSize > 0) {
+						syncLog = syncLog.concat(String.format(", size: %d", this.lastReorgSize));
+					}
+
+					// Log sync info
+					LOGGER.info(syncLog);
 
 					return SynchronizationResult.OK;
 				} finally {
@@ -765,7 +799,7 @@ public class Synchronizer {
 	}
 
 	private SynchronizationResult syncToPeerChain(Repository repository, BlockData commonBlockData, int ourInitialHeight,
-			Peer peer, final int peerHeight, List<BlockSummaryData> peerBlockSummaries) throws DataException, InterruptedException {
+												  Peer peer, final int peerHeight, List<BlockSummaryData> peerBlockSummaries) throws DataException, InterruptedException {
 		final int commonBlockHeight = commonBlockData.getHeight();
 		final byte[] commonBlockSig = commonBlockData.getSignature();
 		String commonBlockSig58 = Base58.encode(commonBlockSig);
@@ -795,19 +829,19 @@ public class Synchronizer {
 			if (Controller.isStopping())
 				return SynchronizationResult.SHUTTING_DOWN;
 
-            // Ensure we don't request more than MAXIMUM_REQUEST_SIZE
-            int numberRequested = Math.min(numberSignaturesRequired, MAXIMUM_REQUEST_SIZE);
+			// Ensure we don't request more than MAXIMUM_REQUEST_SIZE
+			int numberRequested = Math.min(numberSignaturesRequired, MAXIMUM_REQUEST_SIZE);
 
-            // Do we need more signatures?
+			// Do we need more signatures?
 			if (peerBlockSignatures.isEmpty() && numberRequested > 0) {
-                LOGGER.trace(String.format("Requesting %d signature%s after height %d, sig %.8s",
-                        numberRequested, (numberRequested != 1 ? "s" : ""), height, Base58.encode(latestPeerSignature)));
+				LOGGER.trace(String.format("Requesting %d signature%s after height %d, sig %.8s",
+						numberRequested, (numberRequested != 1 ? "s" : ""), height, Base58.encode(latestPeerSignature)));
 
-                peerBlockSignatures = this.getBlockSignatures(peer, latestPeerSignature, numberRequested);
+				peerBlockSignatures = this.getBlockSignatures(peer, latestPeerSignature, numberRequested);
 
-                if (peerBlockSignatures == null || peerBlockSignatures.isEmpty()) {
-                    LOGGER.info(String.format("Peer %s failed to respond with more block signatures after height %d, sig %.8s", peer,
-                            height, Base58.encode(latestPeerSignature)));
+				if (peerBlockSignatures == null || peerBlockSignatures.isEmpty()) {
+					LOGGER.info(String.format("Peer %s failed to respond with more block signatures after height %d, sig %.8s", peer,
+							height, Base58.encode(latestPeerSignature)));
 
 					// Clear our cache of common block summaries for this peer, as they are likely to be invalid
 					CommonBlockData cachedCommonBlockData = peer.getCommonBlockData();
@@ -817,7 +851,7 @@ public class Synchronizer {
                     // If we have already received newer blocks from this peer that what we have already, go ahead and apply them
                     if (peerBlocks.size() > 0) {
 						final BlockData ourLatestBlockData = repository.getBlockRepository().getLastBlock();
-                    	final Block peerLatestBlock = peerBlocks.get(peerBlocks.size() - 1);
+						final Block peerLatestBlock = peerBlocks.get(peerBlocks.size() - 1);
 						final Long minLatestBlockTimestamp = Controller.getMinimumLatestBlockTimestamp();
 						if (ourLatestBlockData != null && peerLatestBlock != null && minLatestBlockTimestamp != null) {
 
@@ -840,8 +874,8 @@ public class Synchronizer {
                     return SynchronizationResult.NO_REPLY;
                 }
 
-                numberSignaturesRequired = peerHeight - height - peerBlockSignatures.size();
-                LOGGER.trace(String.format("Received %s signature%s", peerBlockSignatures.size(), (peerBlockSignatures.size() != 1 ? "s" : "")));
+				numberSignaturesRequired = peerHeight - height - peerBlockSignatures.size();
+				LOGGER.trace(String.format("Received %s signature%s", peerBlockSignatures.size(), (peerBlockSignatures.size() != 1 ? "s" : "")));
 			}
 
 			if (peerBlockSignatures.isEmpty()) {
@@ -924,6 +958,7 @@ public class Synchronizer {
 		// Unwind to common block (unless common block is our latest block)
 		int ourHeight = ourInitialHeight;
 		LOGGER.debug(String.format("Orphaning blocks back to common block height %d, sig %.8s. Our height: %d", commonBlockHeight, commonBlockSig58, ourHeight));
+		int reorgSize = ourHeight - commonBlockHeight;
 
 		BlockData orphanBlockData = repository.getBlockRepository().fromHeight(ourInitialHeight);
 		while (ourHeight > commonBlockHeight) {
@@ -972,12 +1007,113 @@ public class Synchronizer {
 			Controller.getInstance().onNewBlock(newBlock.getBlockData());
 		}
 
+		this.lastReorgSize = reorgSize;
 		return SynchronizationResult.OK;
 	}
 
 	private SynchronizationResult applyNewBlocks(Repository repository, BlockData commonBlockData, int ourInitialHeight,
+												 Peer peer, int peerHeight, List<BlockSummaryData> peerBlockSummaries) throws InterruptedException, DataException {
+
+		final BlockData ourLatestBlockData = repository.getBlockRepository().getLastBlock();
+		if (Settings.getInstance().isFastSyncEnabled() && peer.getPeersVersion() >= PEER_VERSION_160 && ourLatestBlockData.isTrimmed())
+			// This peer supports syncing multiple blocks at once via GetBlocksMessage, and it is enabled in the settings
+			return this.applyNewBlocksUsingFastSync(repository, commonBlockData, ourInitialHeight, peer, peerHeight, peerBlockSummaries);
+		else
+			// Older peer version, or fast sync is disabled in the settings - use slow sync
+			return this.applyNewBlocksUsingSlowSync(repository, commonBlockData, ourInitialHeight, peer, peerHeight, peerBlockSummaries);
+
+	}
+
+	private SynchronizationResult applyNewBlocksUsingFastSync(Repository repository, BlockData commonBlockData, int ourInitialHeight,
+												 Peer peer, int peerHeight, List<BlockSummaryData> peerBlockSummaries) throws InterruptedException, DataException {
+		LOGGER.debug(String.format("Fetching new blocks from peer %s using fast sync", peer));
+
+		final int commonBlockHeight = commonBlockData.getHeight();
+		final byte[] commonBlockSig = commonBlockData.getSignature();
+		byte[] latestPeerSignature = commonBlockSig;
+
+		int ourHeight = ourInitialHeight;
+
+		// Fetch, and apply, blocks from peer
+		int maxBatchHeight = commonBlockHeight + SYNC_BATCH_SIZE;
+
+		// Ensure that we don't request more blocks than specified in the settings
+		int maxBlocksPerRequest = Settings.getInstance().getMaxBlocksPerRequest();
+
+		while (ourHeight < peerHeight && ourHeight < maxBatchHeight) {
+			if (Controller.isStopping())
+				return SynchronizationResult.SHUTTING_DOWN;
+
+			int numberRequested = Math.min(maxBatchHeight - ourHeight, maxBlocksPerRequest);
+
+			LOGGER.trace(String.format("Fetching %d blocks after height %d, sig %.8s from %s", numberRequested, ourHeight, Base58.encode(latestPeerSignature), peer));
+			List<Block> blocks = this.fetchBlocks(repository, peer, latestPeerSignature, numberRequested);
+			if (blocks == null || blocks.isEmpty()) {
+				LOGGER.info(String.format("Peer %s failed to respond with more blocks after height %d, sig %.8s", peer,
+						ourHeight, Base58.encode(latestPeerSignature)));
+				return SynchronizationResult.NO_REPLY;
+			}
+			LOGGER.trace(String.format("Received %d blocks after height %d, sig %.8s from %s", blocks.size(), ourHeight, Base58.encode(latestPeerSignature), peer));
+
+			for (Block newBlock : blocks) {
+				++ourHeight;
+
+				if (Controller.isStopping())
+					return SynchronizationResult.SHUTTING_DOWN;
+
+				if (newBlock == null) {
+					LOGGER.info(String.format("Peer %s failed to respond with block for height %d, sig %.8s", peer,
+							ourHeight, Base58.encode(latestPeerSignature)));
+					return SynchronizationResult.NO_REPLY;
+				}
+
+				if (!newBlock.isSignatureValid()) {
+					LOGGER.info(String.format("Peer %s sent block with invalid signature for height %d, sig %.8s", peer,
+							ourHeight, Base58.encode(latestPeerSignature)));
+					return SynchronizationResult.INVALID_DATA;
+				}
+
+				// Set the repository, because we couldn't do that when originally constructing the Block
+				newBlock.setRepository(repository);
+
+				// Transactions are transmitted without approval status so determine that now
+				for (Transaction transaction : newBlock.getTransactions()) {
+					transaction.setInitialApprovalStatus();
+				}
+
+				ValidationResult blockResult = newBlock.isValid();
+				if (blockResult != ValidationResult.OK) {
+					LOGGER.info(String.format("Peer %s sent invalid block for height %d, sig %.8s: %s", peer,
+							ourHeight, Base58.encode(latestPeerSignature), blockResult.name()));
+					return SynchronizationResult.INVALID_DATA;
+				}
+
+				// Save transactions attached to this block
+				for (Transaction transaction : newBlock.getTransactions()) {
+					TransactionData transactionData = transaction.getTransactionData();
+					repository.getTransactionRepository().save(transactionData);
+				}
+
+				newBlock.process();
+
+				LOGGER.trace(String.format("Processed block height %d, sig %.8s", newBlock.getBlockData().getHeight(), Base58.encode(newBlock.getBlockData().getSignature())));
+
+				repository.saveChanges();
+
+				Controller.getInstance().onNewBlock(newBlock.getBlockData());
+
+				// Update latestPeerSignature so that subsequent batches start requesting from the correct block
+				latestPeerSignature = newBlock.getSignature();
+			}
+
+		}
+
+		return SynchronizationResult.OK;
+	}
+
+	private SynchronizationResult applyNewBlocksUsingSlowSync(Repository repository, BlockData commonBlockData, int ourInitialHeight,
 			Peer peer, int peerHeight, List<BlockSummaryData> peerBlockSummaries) throws InterruptedException, DataException {
-		LOGGER.debug(String.format("Fetching new blocks from peer %s", peer));
+		LOGGER.debug(String.format("Fetching new blocks from peer %s using slow sync", peer));
 
 		final int commonBlockHeight = commonBlockData.getHeight();
 		final byte[] commonBlockSig = commonBlockData.getSignature();
@@ -1098,6 +1234,22 @@ public class Synchronizer {
 		return new Block(repository, blockMessage.getBlockData(), blockMessage.getTransactions(), blockMessage.getAtStates());
 	}
 
+	private List<Block> fetchBlocks(Repository repository, Peer peer, byte[] parentSignature, int numberRequested) throws InterruptedException {
+		Message getBlocksMessage = new GetBlocksMessage(parentSignature, numberRequested);
+
+		Message message = peer.getResponseWithTimeout(getBlocksMessage, FETCH_BLOCKS_TIMEOUT);
+		if (message == null || message.getType() != MessageType.BLOCKS) {
+			return null;
+		}
+
+		BlocksMessage blocksMessage = (BlocksMessage) message;
+		if (blocksMessage == null || blocksMessage.getBlocks() == null) {
+			return null;
+		}
+
+		return blocksMessage.getBlocks();
+	}
+
 	private void populateBlockSummariesMinterLevels(Repository repository, List<BlockSummaryData> blockSummaries) throws DataException {
 		final int firstBlockHeight = blockSummaries.get(0).getHeight();
 

src/main/java/org/qortal/controller/tradebot/BitcoinACCTv1TradeBot.java

@@ -383,15 +383,6 @@ public class BitcoinACCTv1TradeBot implements AcctTradeBot {
 			atData = repository.getATRepository().fromATAddress(tradeBotData.getAtAddress());
 			if (atData == null) {
 				LOGGER.debug(() -> String.format("Unable to fetch trade AT %s from repository", tradeBotData.getAtAddress()));
-
-				// If it has been over 24 hours since we last updated this trade-bot entry then assume AT is never coming back
-				// and so wipe the trade-bot entry
-				if (tradeBotData.getTimestamp() + MAX_AT_CONFIRMATION_PERIOD < NTP.getTime()) {
-					LOGGER.info(() -> String.format("AT %s has been gone for too long - deleting trade-bot entry", tradeBotData.getAtAddress()));
-					repository.getCrossChainRepository().delete(tradeBotData.getTradePrivateKey());
-					repository.saveChanges();
-				}
-
 				return;
 			}
 

src/main/java/org/qortal/controller/tradebot/LitecoinACCTv1TradeBot.java

@@ -387,15 +387,6 @@ public class LitecoinACCTv1TradeBot implements AcctTradeBot {
 			atData = repository.getATRepository().fromATAddress(tradeBotData.getAtAddress());
 			if (atData == null) {
 				LOGGER.debug(() -> String.format("Unable to fetch trade AT %s from repository", tradeBotData.getAtAddress()));
-
-				// If it has been over 24 hours since we last updated this trade-bot entry then assume AT is never coming back
-				// and so wipe the trade-bot entry
-				if (tradeBotData.getTimestamp() + MAX_AT_CONFIRMATION_PERIOD < NTP.getTime()) {
-					LOGGER.info(() -> String.format("AT %s has been gone for too long - deleting trade-bot entry", tradeBotData.getAtAddress()));
-					repository.getCrossChainRepository().delete(tradeBotData.getTradePrivateKey());
-					repository.saveChanges();
-				}
-
 				return;
 			}
 
@@ -725,9 +716,9 @@ public class LitecoinACCTv1TradeBot implements AcctTradeBot {
 			// Not finished yet
 			return;
 
-		// If AT is not REDEEMED then something has gone wrong
-		if (crossChainTradeData.mode != AcctMode.REDEEMED) {
-			// Not redeemed so must be refunded/cancelled
+		// If AT is REFUNDED or CANCELLED then something has gone wrong
+		if (crossChainTradeData.mode == AcctMode.REFUNDED || crossChainTradeData.mode == AcctMode.CANCELLED) {
+			// Alice hasn't redeemed the QORT, so there is no point in trying to redeem the LTC
 			TradeBot.updateTradeBotState(repository, tradeBotData, State.BOB_REFUNDED,
 					() -> String.format("AT %s has auto-refunded - trade aborted", tradeBotData.getAtAddress()));
 

src/main/java/org/qortal/crosschain/Bitcoin.java

@@ -67,7 +67,11 @@ public class Bitcoin extends Bitcoiny {
 						new Server("192.166.219.200", Server.ConnectionType.SSL, 50002),
 						new Server("2ex.digitaleveryware.com", Server.ConnectionType.SSL, 50002),
 						new Server("dxm.no-ip.biz", Server.ConnectionType.SSL, 50002),
-						new Server("caleb.vegas", Server.ConnectionType.SSL, 50002));
+						new Server("caleb.vegas", Server.ConnectionType.SSL, 50002),
+						new Server("ecdsa.net", Server.ConnectionType.SSL, 110),
+						new Server("electrum.hsmiths.com", Server.ConnectionType.SSL, 995),
+						new Server("elec.luggs.co", Server.ConnectionType.SSL, 443),
+						new Server("btc.smsys.me", Server.ConnectionType.SSL, 995));
 			}
 
 			@Override

src/main/java/org/qortal/crosschain/Litecoin.java

@@ -51,7 +51,10 @@ public class Litecoin extends Bitcoiny {
 						new Server("ltc.rentonisk.com", Server.ConnectionType.TCP, 50001),
 						new Server("ltc.rentonisk.com", Server.ConnectionType.SSL, 50002),
 						new Server("electrum-ltc.petrkr.net", Server.ConnectionType.SSL, 60002),
-						new Server("ltc.litepay.ch", Server.ConnectionType.SSL, 50022));
+						new Server("ltc.litepay.ch", Server.ConnectionType.SSL, 50022),
+						new Server("electrum-ltc-bysh.me", Server.ConnectionType.TCP, 50002),
+						new Server("electrum.jochen-hoenicke.de", Server.ConnectionType.TCP, 50005),
+						new Server("node.ispol.sk", Server.ConnectionType.TCP, 50004));
 			}
 
 			@Override

src/main/java/org/qortal/data/block/BlockData.java

@@ -9,7 +9,10 @@ import javax.xml.bind.annotation.XmlAccessorType;
 import javax.xml.bind.annotation.XmlElement;
 import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
 
+import org.qortal.block.BlockChain;
+import org.qortal.settings.Settings;
 import org.qortal.crypto.Crypto;
+import org.qortal.utils.NTP;
 
 // All properties to be converted to JSON via JAX-RS
 @XmlAccessorType(XmlAccessType.FIELD)
@@ -204,6 +207,13 @@ public class BlockData implements Serializable {
 		return this.onlineAccountsSignatures;
 	}
 
+	public boolean isTrimmed() {
+		long onlineAccountSignaturesTrimmedTimestamp = NTP.getTime() - BlockChain.getInstance().getOnlineAccountSignaturesMaxLifetime();
+		long currentTrimmableTimestamp = NTP.getTime() - Settings.getInstance().getAtStatesMaxLifetime();
+		long blockTimestamp = this.getTimestamp();
+		return blockTimestamp < onlineAccountSignaturesTrimmedTimestamp && blockTimestamp < currentTrimmableTimestamp;
+	}
+
 	// JAXB special
 
 	@XmlElement(name = "minterAddress")

src/main/java/org/qortal/network/Network.java

@@ -72,7 +72,8 @@ public class Network {
     private static final String[] INITIAL_PEERS = new String[]{
             "node1.qortal.org", "node2.qortal.org", "node3.qortal.org", "node4.qortal.org", "node5.qortal.org",
             "node6.qortal.org", "node7.qortal.org", "node8.qortal.org", "node9.qortal.org", "node10.qortal.org",
-            "node.qortal.ru", "node2.qortal.ru", "node3.qortal.ru", "node.qortal.uk"
+            "node.qortal.ru", "node2.qortal.ru", "node3.qortal.ru", "node.qortal.uk", "node22.qortal.org",
+            "cinfu1.crowetic.com", "node.cwd.systems"
     };
 
     private static final long NETWORK_EPC_KEEPALIVE = 10L; // seconds
@@ -80,6 +81,8 @@ public class Network {
     public static final int MAX_SIGNATURES_PER_REPLY = 500;
     public static final int MAX_BLOCK_SUMMARIES_PER_REPLY = 500;
 
+    private static final long DISCONNECTION_CHECK_INTERVAL = 10 * 1000L; // milliseconds
+
     // Generate our node keys / ID
     private final Ed25519PrivateKeyParameters edPrivateKeyParams = new Ed25519PrivateKeyParameters(new SecureRandom());
     private final Ed25519PublicKeyParameters edPublicKeyParams = edPrivateKeyParams.generatePublicKey();
@@ -89,6 +92,8 @@ public class Network {
     private final int minOutboundPeers;
     private final int maxPeers;
 
+    private long nextDisconnectionCheck = 0L;
+
     private final List<PeerData> allKnownPeers = new ArrayList<>();
     private final List<Peer> connectedPeers = new ArrayList<>();
     private final List<PeerAddress> selfPeers = new ArrayList<>();
@@ -150,9 +155,23 @@ public class Network {
         }
 
         // Load all known peers from repository
-        try (Repository repository = RepositoryManager.getRepository()) {
-            synchronized (this.allKnownPeers) {
-                this.allKnownPeers.addAll(repository.getNetworkRepository().getAllPeers());
+        synchronized (this.allKnownPeers) { List<String> fixedNetwork = Settings.getInstance().getFixedNetwork();
+            if (fixedNetwork != null && !fixedNetwork.isEmpty()) {
+                Long addedWhen = NTP.getTime();
+                String addedBy = "fixedNetwork";
+                List<PeerAddress> peerAddresses = new ArrayList<>();
+                for (String address : fixedNetwork) {
+                    PeerAddress peerAddress = PeerAddress.fromString(address);
+                    peerAddresses.add(peerAddress);
+                }
+                List<PeerData> peers = peerAddresses.stream()
+                        .map(peerAddress -> new PeerData(peerAddress, addedWhen, addedBy))
+                        .collect(Collectors.toList());
+                this.allKnownPeers.addAll(peers);
+            } else {
+                try (Repository repository = RepositoryManager.getRepository()) {
+                    this.allKnownPeers.addAll(repository.getNetworkRepository().getAllPeers());
+                }
             }
         }
 
@@ -508,14 +527,24 @@ public class Network {
         if (socketChannel == null) {
             return;
         }
+        PeerAddress address = PeerAddress.fromSocket(socketChannel.socket());
+        List<String> fixedNetwork = Settings.getInstance().getFixedNetwork();
+        if (fixedNetwork != null && !fixedNetwork.isEmpty() && ipNotInFixedList(address, fixedNetwork)) {
+            try {
+                LOGGER.debug("Connection discarded from peer {} as not in the fixed network list", address);
+                socketChannel.close();
+            } catch (IOException e) {
+                // IGNORE
+            }
+            return;
+        }
 
         final Long now = NTP.getTime();
         Peer newPeer;
 
         try {
             if (now == null) {
-                LOGGER.debug("Connection discarded from peer {} due to lack of NTP sync",
-                        PeerAddress.fromSocket(socketChannel.socket()));
+                LOGGER.debug("Connection discarded from peer {} due to lack of NTP sync", address);
                 socketChannel.close();
                 return;
             }
@@ -523,12 +552,12 @@ public class Network {
             synchronized (this.connectedPeers) {
                 if (connectedPeers.size() >= maxPeers) {
                     // We have enough peers
-                    LOGGER.debug("Connection discarded from peer {}", PeerAddress.fromSocket(socketChannel.socket()));
+                    LOGGER.debug("Connection discarded from peer {} because the server is full", address);
                     socketChannel.close();
                     return;
                 }
 
-                LOGGER.debug("Connection accepted from peer {}", PeerAddress.fromSocket(socketChannel.socket()));
+                LOGGER.debug("Connection accepted from peer {}", address);
 
                 newPeer = new Peer(socketChannel, channelSelector);
                 this.connectedPeers.add(newPeer);
@@ -536,6 +565,7 @@ public class Network {
         } catch (IOException e) {
             if (socketChannel.isOpen()) {
                 try {
+                    LOGGER.debug("Connection failed from peer {} while connecting/closing", address);
                     socketChannel.close();
                 } catch (IOException ce) {
                     // Couldn't close?
@@ -547,6 +577,16 @@ public class Network {
         this.onPeerReady(newPeer);
     }
 
+    private boolean ipNotInFixedList(PeerAddress address, List<String> fixedNetwork) {
+        for (String ipAddress : fixedNetwork) {
+            String[] bits = ipAddress.split(":");
+            if (bits.length >= 1 && bits.length <= 2 && address.getHost().equals(bits[0])) {
+                return false;
+            }
+        }
+        return true;
+    }
+
     private Peer getConnectablePeer(final Long now) throws InterruptedException {
         // We can't block here so use tryRepository(). We don't NEED to connect a new peer.
         try (Repository repository = RepositoryManager.tryRepository()) {
@@ -576,6 +616,8 @@ public class Network {
                 // Don't consider already connected peers (resolved address match)
                 // XXX This might be too slow if we end up waiting a long time for hostnames to resolve via DNS
                 peers.removeIf(isResolvedAsConnectedPeer);
+
+                this.checkLongestConnection(now);
             }
 
             // Any left?
@@ -633,6 +675,29 @@ public class Network {
         return null;
     }
 
+    private void checkLongestConnection(Long now) {
+        if (now == null || now < nextDisconnectionCheck) {
+            return;
+        }
+
+        // Find peers that have reached their maximum connection age, and disconnect them
+        List<Peer> peersToDisconnect = this.connectedPeers.stream()
+                .filter(peer -> !peer.isSyncInProgress())
+                .filter(peer -> peer.hasReachedMaxConnectionAge())
+                .collect(Collectors.toList());
+
+        if (peersToDisconnect != null && peersToDisconnect.size() > 0) {
+            for (Peer peer : peersToDisconnect) {
+                LOGGER.info("Forcing disconnection of peer {} because connection age ({} ms) " +
+                        "has reached the maximum ({} ms)", peer, peer.getConnectionAge(), peer.getMaxConnectionAge());
+                peer.disconnect("Connection age too old");
+            }
+        }
+
+        // Check again after a minimum fixed interval
+        nextDisconnectionCheck = now + DISCONNECTION_CHECK_INTERVAL;
+    }
+
     // Peer callbacks
 
     protected void wakeupChannelSelector() {
@@ -1115,6 +1180,10 @@ public class Network {
 
     private boolean mergePeers(Repository repository, String addedBy, long addedWhen, List<PeerAddress> peerAddresses)
             throws DataException {
+        List<String> fixedNetwork = Settings.getInstance().getFixedNetwork();
+        if (fixedNetwork != null && !fixedNetwork.isEmpty()) {
+            return false;
+        }
         List<PeerData> newPeers;
         synchronized (this.allKnownPeers) {
             for (PeerData knownPeerData : this.allKnownPeers) {

src/main/java/org/qortal/network/Peer.java

@@ -47,6 +47,11 @@ public class Peer {
      */
     private static final int RESPONSE_TIMEOUT = 3000; // ms
 
+    /**
+     * Maximum time to wait for a peer to respond with blocks (ms)
+     */
+    public static final int FETCH_BLOCKS_TIMEOUT = 10000;
+
     /**
      * Interval between PING messages to a peer. (ms)
      * <p>
@@ -79,6 +84,7 @@ public class Peer {
     private Handshake handshakeStatus = Handshake.STARTED;
     private volatile boolean handshakeMessagePending = false;
     private long handshakeComplete = -1L;
+    private long maxConnectionAge = 0L;
 
     /**
      * Timestamp of when socket was accepted, or connected.
@@ -96,6 +102,8 @@ public class Peer {
 
     byte[] ourChallenge;
 
+    private boolean syncInProgress = false;
+
     // Versioning
     public static final Pattern VERSION_PATTERN = Pattern.compile(Controller.VERSION_PREFIX
             + "(\\d{1,3})\\.(\\d{1,5})\\.(\\d{1,5})");
@@ -192,10 +200,24 @@ public class Peer {
             this.handshakeStatus = handshakeStatus;
             if (handshakeStatus.equals(Handshake.COMPLETED)) {
                 this.handshakeComplete = System.currentTimeMillis();
+                this.generateRandomMaxConnectionAge();
             }
         }
     }
 
+    private void generateRandomMaxConnectionAge() {
+        // Retrieve the min and max connection time from the settings, and calculate the range
+        final int minPeerConnectionTime = Settings.getInstance().getMinPeerConnectionTime();
+        final int maxPeerConnectionTime = Settings.getInstance().getMaxPeerConnectionTime();
+        final int peerConnectionTimeRange = maxPeerConnectionTime - minPeerConnectionTime;
+
+        // Generate a random number between the min and the max
+        Random random = new Random();
+        this.maxConnectionAge = (random.nextInt(peerConnectionTimeRange) + minPeerConnectionTime) * 1000L;
+        LOGGER.debug(String.format("Generated max connection age for peer %s. Min: %ds, max: %ds, range: %ds, random max: %dms", this, minPeerConnectionTime, maxPeerConnectionTime, peerConnectionTimeRange, this.maxConnectionAge));
+
+    }
+
     protected void resetHandshakeMessagePending() {
         this.handshakeMessagePending = false;
     }
@@ -325,6 +347,14 @@ public class Peer {
         }
     }
 
+    public boolean isSyncInProgress() {
+        return this.syncInProgress;
+    }
+
+    public void setSyncInProgress(boolean syncInProgress) {
+        this.syncInProgress = syncInProgress;
+    }
+
     @Override
     public String toString() {
         // Easier, and nicer output, than peer.getRemoteSocketAddress()
@@ -519,12 +549,22 @@ public class Peer {
     }
 
     /**
-     * Attempt to send Message to peer.
+     * Attempt to send Message to peer, using default RESPONSE_TIMEOUT.
      *
      * @param message message to be sent
      * @return <code>true</code> if message successfully sent; <code>false</code> otherwise
      */
     public boolean sendMessage(Message message) {
+        return this.sendMessageWithTimeout(message, RESPONSE_TIMEOUT);
+    }
+
+    /**
+     * Attempt to send Message to peer, using custom timeout.
+     *
+     * @param message message to be sent
+     * @return <code>true</code> if message successfully sent; <code>false</code> otherwise
+     */
+    public boolean sendMessageWithTimeout(Message message, int timeout) {
         if (!this.socketChannel.isOpen()) {
             return false;
         }
@@ -558,7 +598,7 @@ public class Peer {
                          */
                         Thread.sleep(1L); //NOSONAR squid:S2276
 
-                        if (System.currentTimeMillis() - sendStart > RESPONSE_TIMEOUT) {
+                        if (System.currentTimeMillis() - sendStart > timeout) {
                             // We've taken too long to send this message
                             return false;
                         }
@@ -579,7 +619,7 @@ public class Peer {
     }
 
     /**
-     * Send message to peer and await response.
+     * Send message to peer and await response, using default RESPONSE_TIMEOUT.
      * <p>
      * Message is assigned a random ID and sent.
      * If a response with matching ID is received then it is returned to caller.
@@ -593,6 +633,24 @@ public class Peer {
      * @throws InterruptedException if interrupted while waiting
      */
     public Message getResponse(Message message) throws InterruptedException {
+        return getResponseWithTimeout(message, RESPONSE_TIMEOUT);
+    }
+
+    /**
+     * Send message to peer and await response.
+     * <p>
+     * Message is assigned a random ID and sent.
+     * If a response with matching ID is received then it is returned to caller.
+     * <p>
+     * If no response with matching ID within timeout, or some other error/exception occurs,
+     * then return <code>null</code>.<br>
+     * (Assume peer will be rapidly disconnected after this).
+     *
+     * @param message message to send
+     * @return <code>Message</code> if valid response received; <code>null</code> if not or error/exception occurs
+     * @throws InterruptedException if interrupted while waiting
+     */
+    public Message getResponseWithTimeout(Message message, int timeout) throws InterruptedException {
         BlockingQueue<Message> blockingQueue = new ArrayBlockingQueue<>(1);
 
         // Assign random ID to this message
@@ -607,13 +665,13 @@ public class Peer {
         message.setId(id);
 
         // Try to send message
-        if (!this.sendMessage(message)) {
+        if (!this.sendMessageWithTimeout(message, timeout)) {
             this.replyQueues.remove(id);
             return null;
         }
 
         try {
-            return blockingQueue.poll(RESPONSE_TIMEOUT, TimeUnit.MILLISECONDS);
+            return blockingQueue.poll(timeout, TimeUnit.MILLISECONDS);
         } finally {
             this.replyQueues.remove(id);
         }
@@ -777,4 +835,12 @@ public class Peer {
         }
         return handshakeComplete;
     }
+
+    public long getMaxConnectionAge() {
+        return maxConnectionAge;
+    }
+
+    public boolean hasReachedMaxConnectionAge() {
+        return this.getConnectionAge() > this.getMaxConnectionAge();
+    }
 }

src/main/java/org/qortal/network/message/BlocksMessage.java

@@ -0,0 +1,91 @@
+package org.qortal.network.message;
+
+import com.google.common.primitives.Ints;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.qortal.block.Block;
+import org.qortal.data.at.ATStateData;
+import org.qortal.data.block.BlockData;
+import org.qortal.data.transaction.TransactionData;
+import org.qortal.transform.TransformationException;
+import org.qortal.transform.block.BlockTransformer;
+import org.qortal.utils.Triple;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.UnsupportedEncodingException;
+import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.List;
+
+public class BlocksMessage extends Message {
+
+	private static final Logger LOGGER = LogManager.getLogger(BlocksMessage.class);
+
+	private List<Block> blocks;
+
+	public BlocksMessage(List<Block> blocks) {
+		this(-1, blocks);
+	}
+
+	private BlocksMessage(int id, List<Block> blocks) {
+		super(id, MessageType.BLOCKS);
+
+		this.blocks = blocks;
+	}
+
+	public List<Block> getBlocks() {
+		return this.blocks;
+	}
+
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException {
+
+		int count = bytes.getInt();
+		List<Block> blocks = new ArrayList<>();
+
+		for (int i = 0; i < count; ++i) {
+			int height = bytes.getInt();
+
+			try {
+				boolean finalBlockInBuffer = (i == count-1);
+
+				Triple<BlockData, List<TransactionData>, List<ATStateData>> blockInfo = null;
+				blockInfo = BlockTransformer.fromByteBuffer(bytes, finalBlockInBuffer);
+				BlockData blockData = blockInfo.getA();
+				blockData.setHeight(height);
+
+				// We are unable to obtain a valid Repository instance here, so set it to null and we will attach it later
+				Block block = new Block(null, blockData, blockInfo.getB(), blockInfo.getC());
+				blocks.add(block);
+
+			} catch (TransformationException e) {
+				return null;
+			}
+
+		}
+
+		return new BlocksMessage(id, blocks);
+	}
+
+	@Override
+	protected byte[] toData() {
+		try {
+			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+
+			bytes.write(Ints.toByteArray(this.blocks.size()));
+
+			for (Block block : this.blocks) {
+				bytes.write(Ints.toByteArray(block.getBlockData().getHeight()));
+				bytes.write(BlockTransformer.toBytes(block));
+			}
+			LOGGER.trace(String.format("Total length of %d blocks is %d bytes", this.blocks.size(), bytes.size()));
+
+			return bytes.toByteArray();
+		} catch (IOException e) {
+			return null;
+		} catch (TransformationException e) {
+			return null;
+		}
+	}
+
+}

src/main/java/org/qortal/network/message/GetBlocksMessage.java

@@ -0,0 +1,65 @@
+package org.qortal.network.message;
+
+import com.google.common.primitives.Ints;
+import org.qortal.transform.Transformer;
+import org.qortal.transform.block.BlockTransformer;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.UnsupportedEncodingException;
+import java.nio.ByteBuffer;
+
+public class GetBlocksMessage extends Message {
+
+	private static final int BLOCK_SIGNATURE_LENGTH = BlockTransformer.BLOCK_SIGNATURE_LENGTH;
+
+	private byte[] parentSignature;
+	private int numberRequested;
+
+	public GetBlocksMessage(byte[] parentSignature, int numberRequested) {
+		this(-1, parentSignature, numberRequested);
+	}
+
+	private GetBlocksMessage(int id, byte[] parentSignature, int numberRequested) {
+		super(id, MessageType.GET_BLOCKS);
+
+		this.parentSignature = parentSignature;
+		this.numberRequested = numberRequested;
+	}
+
+	public byte[] getParentSignature() {
+		return this.parentSignature;
+	}
+
+	public int getNumberRequested() {
+		return this.numberRequested;
+	}
+
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException {
+		if (bytes.remaining() != BLOCK_SIGNATURE_LENGTH + Transformer.INT_LENGTH)
+			return null;
+
+		byte[] parentSignature = new byte[BLOCK_SIGNATURE_LENGTH];
+		bytes.get(parentSignature);
+
+		int numberRequested = bytes.getInt();
+
+		return new GetBlocksMessage(id, parentSignature, numberRequested);
+	}
+
+	@Override
+	protected byte[] toData() {
+		try {
+			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+
+			bytes.write(this.parentSignature);
+
+			bytes.write(Ints.toByteArray(this.numberRequested));
+
+			return bytes.toByteArray();
+		} catch (IOException e) {
+			return null;
+		}
+	}
+
+}

src/main/java/org/qortal/network/message/GetOnlineAccountsMessage.java

@@ -6,6 +6,7 @@ import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.stream.Collectors;
 
 import org.qortal.data.network.OnlineAccountData;
 import org.qortal.transform.Transformer;
@@ -25,7 +26,7 @@ public class GetOnlineAccountsMessage extends Message {
 	private GetOnlineAccountsMessage(int id, List<OnlineAccountData> onlineAccounts) {
 		super(id, MessageType.GET_ONLINE_ACCOUNTS);
 
-		this.onlineAccounts = onlineAccounts;
+		this.onlineAccounts = onlineAccounts.stream().limit(MAX_ACCOUNT_COUNT).collect(Collectors.toList());
 	}
 
 	public List<OnlineAccountData> getOnlineAccounts() {
@@ -35,12 +36,9 @@ public class GetOnlineAccountsMessage extends Message {
 	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException {
 		final int accountCount = bytes.getInt();
 
-		if (accountCount > MAX_ACCOUNT_COUNT)
-			return null;
-
 		List<OnlineAccountData> onlineAccounts = new ArrayList<>(accountCount);
 
-		for (int i = 0; i < accountCount; ++i) {
+		for (int i = 0; i < Math.min(MAX_ACCOUNT_COUNT, accountCount); ++i) {
 			long timestamp = bytes.getLong();
 
 			byte[] publicKey = new byte[Transformer.PUBLIC_KEY_LENGTH];

src/main/java/org/qortal/network/message/Message.java

@@ -25,7 +25,7 @@ public abstract class Message {
 	private static final int MAGIC_LENGTH = 4;
 	private static final int CHECKSUM_LENGTH = 4;
 
-	private static final int MAX_DATA_SIZE = 1024 * 1024; // 1MB
+	private static final int MAX_DATA_SIZE = 10 * 1024 * 1024; // 10MB
 
 	@SuppressWarnings("serial")
 	public static class MessageException extends Exception {
@@ -80,7 +80,10 @@ public abstract class Message {
 		GET_ONLINE_ACCOUNTS(81),
 
 		ARBITRARY_DATA(90),
-		GET_ARBITRARY_DATA(91);
+		GET_ARBITRARY_DATA(91),
+
+		BLOCKS(100),
+		GET_BLOCKS(101);
 
 		public final int value;
 		public final Method fromByteBufferMethod;

src/main/java/org/qortal/network/message/OnlineAccountsMessage.java

@@ -6,6 +6,7 @@ import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.stream.Collectors;
 
 import org.qortal.data.network.OnlineAccountData;
 import org.qortal.transform.Transformer;
@@ -25,7 +26,7 @@ public class OnlineAccountsMessage extends Message {
 	private OnlineAccountsMessage(int id, List<OnlineAccountData> onlineAccounts) {
 		super(id, MessageType.ONLINE_ACCOUNTS);
 
-		this.onlineAccounts = onlineAccounts;
+		this.onlineAccounts = onlineAccounts.stream().limit(MAX_ACCOUNT_COUNT).collect(Collectors.toList());
 	}
 
 	public List<OnlineAccountData> getOnlineAccounts() {
@@ -35,12 +36,9 @@ public class OnlineAccountsMessage extends Message {
 	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws UnsupportedEncodingException {
 		final int accountCount = bytes.getInt();
 
-		if (accountCount > MAX_ACCOUNT_COUNT)
-			return null;
-
 		List<OnlineAccountData> onlineAccounts = new ArrayList<>(accountCount);
 
-		for (int i = 0; i < accountCount; ++i) {
+		for (int i = 0; i < Math.min(MAX_ACCOUNT_COUNT, accountCount); ++i) {
 			long timestamp = bytes.getLong();
 
 			byte[] signature = new byte[Transformer.SIGNATURE_LENGTH];

src/main/java/org/qortal/settings/Settings.java

@@ -5,6 +5,7 @@ import java.io.FileNotFoundException;
 import java.io.FileReader;
 import java.io.IOException;
 import java.io.Reader;
+import java.util.List;
 import java.util.Locale;
 
 import javax.xml.bind.JAXBContext;
@@ -132,6 +133,22 @@ public class Settings {
 	 * If false, sync will be blocked both ways, and they will not appear in the peers list */
 	private boolean allowConnectionsWithOlderPeerVersions = true;
 
+	/** Minimum time (in seconds) that we should attempt to remain connected to a peer for */
+	private int minPeerConnectionTime = 2 * 60; // seconds
+	/** Maximum time (in seconds) that we should attempt to remain connected to a peer for */
+	private int maxPeerConnectionTime = 20 * 60; // seconds
+
+	/** Whether to sync multiple blocks at once in normal operation */
+	private boolean fastSyncEnabled = true;
+	/** Whether to sync multiple blocks at once when the peer has a different chain */
+	private boolean fastSyncEnabledWhenResolvingFork = true;
+	/** Maximum number of blocks to request at once */
+	private int maxBlocksPerRequest = 100;
+	/** Maximum number of blocks this node will serve in a single response */
+	private int maxBlocksPerResponse = 200;
+	/** Maximum number of untrimmed blocks this node will serve in a single response */
+	private int maxUntrimmedBlocksPerResponse = 10;
+
 	// Which blockchains this node is running
 	private String blockchainConfig = null; // use default from resources
 	private BitcoinNet bitcoinNet = BitcoinNet.MAIN;
@@ -147,6 +164,7 @@ public class Settings {
 	private String repositoryPath = "db";
 	/** Repository connection pool size. Needs to be a bit bigger than maxNetworkThreadPoolSize */
 	private int repositoryConnectionPoolSize = 100;
+	private List<String> fixedNetwork;
 
 	// Auto-update sources
 	private String[] autoUpdateRepos = new String[] {
@@ -423,6 +441,10 @@ public class Settings {
 
 	public boolean getAllowConnectionsWithOlderPeerVersions() { return this.allowConnectionsWithOlderPeerVersions; }
 
+	public int getMinPeerConnectionTime() { return this.minPeerConnectionTime; }
+
+	public int getMaxPeerConnectionTime() { return this.maxPeerConnectionTime; }
+
 	public String getBlockchainConfig() {
 		return this.blockchainConfig;
 	}
@@ -451,6 +473,20 @@ public class Settings {
 		return this.repositoryConnectionPoolSize;
 	}
 
+	public boolean isFastSyncEnabled() {
+		return this.fastSyncEnabled;
+	}
+
+	public boolean isFastSyncEnabledWhenResolvingFork() {
+		return this.fastSyncEnabledWhenResolvingFork;
+	}
+
+	public int getMaxBlocksPerRequest() { return this.maxBlocksPerRequest; }
+
+	public int getMaxBlocksPerResponse() { return this.maxBlocksPerResponse; }
+
+	public int getMaxUntrimmedBlocksPerResponse() { return this.maxUntrimmedBlocksPerResponse; }
+
 	public boolean isAutoUpdateEnabled() {
 		return this.autoUpdateEnabled;
 	}
@@ -507,4 +543,7 @@ public class Settings {
 		return this.onlineSignaturesTrimBatchSize;
 	}
 
+	public List<String> getFixedNetwork() {
+		return fixedNetwork;
+	}
 }

src/main/java/org/qortal/transaction/Transaction.java

@@ -315,6 +315,10 @@ public abstract class Transaction {
 		return this.transactionData;
 	}
 
+	public void setRepository(Repository repository) {
+		this.repository = repository;
+	}
+
 	// More information
 
 	public static long getDeadline(TransactionData transactionData) {

src/main/java/org/qortal/transform/block/BlockTransformer.java

@@ -74,19 +74,30 @@ public class BlockTransformer extends Transformer {
 	}
 
 	/**
-	 * Extract block data and transaction data from serialized bytes.
-	 * 
+	 * Extract block data and transaction data from serialized bytes containing a single block.
+	 *
 	 * @param bytes
 	 * @return BlockData and a List of transactions.
 	 * @throws TransformationException
 	 */
 	public static Triple<BlockData, List<TransactionData>, List<ATStateData>> fromByteBuffer(ByteBuffer byteBuffer) throws TransformationException {
+		return BlockTransformer.fromByteBuffer(byteBuffer, true);
+	}
+
+	/**
+	 * Extract block data and transaction data from serialized bytes containing one or more blocks.
+	 * 
+	 * @param bytes
+	 * @return the next block's BlockData and a List of transactions.
+	 * @throws TransformationException
+	 */
+	public static Triple<BlockData, List<TransactionData>, List<ATStateData>> fromByteBuffer(ByteBuffer byteBuffer, boolean finalBlockInBuffer) throws TransformationException {
 		int version = byteBuffer.getInt();
 
-		if (byteBuffer.remaining() < BASE_LENGTH + AT_BYTES_LENGTH - VERSION_LENGTH)
+		if (finalBlockInBuffer && byteBuffer.remaining() < BASE_LENGTH + AT_BYTES_LENGTH - VERSION_LENGTH)
 			throw new TransformationException("Byte data too short for Block");
 
-		if (byteBuffer.remaining() > BlockChain.getInstance().getMaxBlockSize())
+		if (finalBlockInBuffer && byteBuffer.remaining() > BlockChain.getInstance().getMaxBlockSize())
 			throw new TransformationException("Byte data too long for Block");
 
 		long timestamp = byteBuffer.getLong();
@@ -210,7 +221,8 @@ public class BlockTransformer extends Transformer {
 			byteBuffer.get(onlineAccountsSignatures);
 		}
 
-		if (byteBuffer.hasRemaining())
+		// We should only complain about excess byte data if we aren't expecting more blocks in this ByteBuffer
+		if (finalBlockInBuffer && byteBuffer.hasRemaining())
 			throw new TransformationException("Excess byte data found after parsing Block");
 
 		// We don't have a height!

tools/block-timings.sh

@@ -69,11 +69,13 @@ function fetch_and_process_blocks {
     online_accounts_count=$(echo "${block_minting_info}" | jq -r .onlineAccountsCount)
     key_distance_ratio=$(echo "${block_minting_info}" | jq -r .keyDistanceRatio)
     time_delta=$(echo "${block_minting_info}" | jq -r .timeDelta)
+    timestamp=$(echo "${block_minting_info}" | jq -r .timestamp)
 
     time_offset=$(calculate_time_offset "${key_distance_ratio}")
     block_time=$((target-deviation+time_offset))
 
     echo "=== BLOCK ${height} ==="
+    echo "Timestamp: ${timestamp}"
     echo "Minter level: ${minter_level}"
     echo "Online accounts: ${online_accounts_count}"
     echo "Key distance ratio: ${key_distance_ratio}"

tools/build-release.sh

@@ -1,7 +1,8 @@
 #!/usr/bin/env bash
 
 # Change this to where AdvancedInstaller outputs built EXE installers
-WINDOWS_INSTALLER_DIR=/home/transfer/Qortal/Qortal-SetupFiles
+SCRIPT_DIR=$(dirname $(realpath "$0"))
+WINDOWS_INSTALLER_DIR="${SCRIPT_DIR}/../WindowsInstaller/Qortal-SetupFiles"
 
 set -e
 shopt -s expand_aliases
@@ -16,6 +17,16 @@ saved_pwd=$PWD
 
 alias SHA256='(sha256 -q || sha256sum | cut -d" " -f1) 2>/dev/null'
 
+function 3hash {
+  local zip_src=$1
+  local md5hash=$(md5 ${zip_src} | awk '{ print $NF }')
+  local sha1hash=$(shasum ${zip_src} | awk '{ print $1 }')
+  local sha256hash=$(sha256sum ${zip_src} | awk '{ print $1 }')
+  echo "\`MD5: ${md5hash}\`"
+  echo "\`SHA1: ${sha1hash}\`"
+  echo "\`SHA256: ${sha256hash}\`"
+}
+
 # Check we are within a git repo
 git_dir=$( git rev-parse --show-toplevel )
 if [ -z "${git_dir}" ]; then
@@ -27,7 +38,7 @@ fi
 cd ${git_dir}
 
 # Check we are in 'master' branch
-# branch_name=$( git symbolic-ref -q HEAD )
+# branch_name=$( git symbolic-ref -q HEAD ) || echo "Cannot determine branch name" && exit 1
 # branch_name=${branch_name##refs/heads/}
 # if [ "${branch_name}" != "master" ]; then
 	# echo "Unexpected current branch '${branch_name}' - expecting 'master'"
@@ -56,7 +67,7 @@ git_url=https://github.com/${git_url##*:}
 git_url=${git_url%%.git}
 
 # Check for EXE
-exe=${project^}-${git_tag#v}.exe
+exe=${project}-${git_tag#v}.exe
 exe_src="${WINDOWS_INSTALLER_DIR}/${exe}"
 if [ ! -r "${exe_src}" ]; then
 	echo "Cannot find EXE installer at ${exe_src}"

tools/build-zip.sh

@@ -21,13 +21,13 @@ fi
 cd ${git_dir}
 
 # Check we are in 'master' branch
-branch_name=$( git symbolic-ref -q HEAD )
-branch_name=${branch_name##refs/heads/}
-echo "Current git branch: ${branch_name}"
-if [ "${branch_name}" != "master" ]; then
-	echo "Unexpected current branch '${branch_name}' - expecting 'master'"
-	exit 1
-fi
+# branch_name=$( git symbolic-ref -q HEAD ) || echo "Cannot determine branch name" && exit 1
+# branch_name=${branch_name##refs/heads/}
+# echo "Current git branch: ${branch_name}"
+# if [ "${branch_name}" != "master" ]; then
+# 	echo "Unexpected current branch '${branch_name}' - expecting 'master'"
+# 	exit 1
+# fi
 
 # Determine project name
 project=$( perl -n -e 'if (m/<artifactId>(\w+)<.artifactId>/) { print $1; exit }' pom.xml $)
@@ -60,7 +60,7 @@ git show HEAD:stop.sh > ${build_dir}/stop.sh
 
 printf "{\n}\n" > ${build_dir}/settings.json
 
-touch -d ${commit_ts%%+??:??} ${build_dir} ${build_dir}/*
+gtouch -d ${commit_ts%%+??:??} ${build_dir} ${build_dir}/*
 
 rm -f ${saved_pwd}/${project}.zip
 (cd ${build_dir}/..; 7z a -r -tzip ${saved_pwd}/${project}-${git_tag#v}.zip ${project}/)