Some changes to how block chain download is done:

- Progress is now made available
- Fixes bug: can now wait for downloads of chains < 500 blocks
- Flesh out VersionMessage parsing, send BitCoinJ name in subVer field

src/com/google/bitcoin/core/AddressMessage.java

@@ -24,7 +24,7 @@ public class AddressMessage extends Message {
             throw new ProtocolException("Address message too large.");
         addresses = new ArrayList<PeerAddress>((int)numAddresses);
         for (int i = 0; i < numAddresses; i++) {
-            PeerAddress addr = new PeerAddress(params, bytes, cursor);
+            PeerAddress addr = new PeerAddress(params, bytes, cursor, protocolVersion);
             addresses.add(addr);
             cursor += addr.getMessageSize();
         }

src/com/google/bitcoin/core/GetBlocksMessage.java

@@ -48,7 +48,7 @@ public class GetBlocksMessage extends Message {
         try {
             ByteArrayOutputStream buf = new ByteArrayOutputStream();
             // Version, for some reason.
-            Utils.uint32ToByteStreamLE(VersionMessage.PROTOCOL_VERSION, buf);
+            Utils.uint32ToByteStreamLE(NetworkParameters.PROTOCOL_VERSION, buf);
             // Then a vector of block hashes. This is actually a "block locator", a set of block
             // identifiers that spans the entire chain with exponentially increasing gaps between
             // them, until we end up at the genesis block. See CBlockLocator::Set()

src/com/google/bitcoin/core/Message.java

@@ -16,10 +16,7 @@
 
 package com.google.bitcoin.core;
 
-import java.io.ByteArrayOutputStream;
+import java.io.*;
-import java.io.IOException;
-import java.io.OutputStream;
-import java.io.Serializable;
 import java.math.BigInteger;
 import java.util.Arrays;
 
@@ -44,8 +41,11 @@ public abstract class Message implements Serializable {
     // Note that it's relative to the start of the array NOT the start of the message.
     protected transient int cursor;
 
+    // The raw message bytes themselves.
     protected transient byte[] bytes;
 
+    protected transient int protocolVersion;
+
     // This will be saved by subclasses that implement Serializable.
     protected NetworkParameters params;
 
@@ -58,7 +58,8 @@ public abstract class Message implements Serializable {
     }
 
     @SuppressWarnings("unused")
-    Message(NetworkParameters params, byte[] msg, int offset) throws ProtocolException {
+    Message(NetworkParameters params, byte[] msg, int offset, int protocolVersion) throws ProtocolException {
+        this.protocolVersion = protocolVersion;
         this.params = params;
         this.bytes = msg;
         this.cursor = this.offset = offset;
@@ -75,6 +76,10 @@ public abstract class Message implements Serializable {
         this.bytes = null;
     }
 
+    Message(NetworkParameters params, byte[] msg, int offset) throws ProtocolException {
+        this(params, msg, offset, NetworkParameters.PROTOCOL_VERSION);
+    }
+    
     // These methods handle the serialization/deserialization using the custom BitCoin protocol.
     // It's somewhat painful to work with in Java, so some of these objects support a second 
     // serialization mechanism - the standard Java serialization system. This is used when things 
@@ -141,4 +146,20 @@ public abstract class Message implements Serializable {
         cursor += length;
         return b;
     }
+
+    String readStr() {
+        VarInt varInt = new VarInt(bytes, cursor);
+        if (varInt.value == 0) {
+            cursor += 1;
+            return "";
+        }
+        byte[] characters = new byte[(int)varInt.value];
+        System.arraycopy(bytes, cursor, characters, 0, characters.length);
+        cursor += varInt.getSizeInBytes();
+        try {
+            return new String(characters, "UTF-8");
+        } catch (UnsupportedEncodingException e) {
+            throw new RuntimeException(e);  // Cannot happen, UTF-8 is always supported.
+        }
+    }
 }

src/com/google/bitcoin/core/NetworkConnection.java

@@ -55,7 +55,8 @@ public class NetworkConnection {
     private final InetAddress remoteIp;
     private boolean usesChecksumming;
     private final NetworkParameters params;
-    static final private boolean PROTOCOL_LOG = false;
+    private final VersionMessage versionMessage;
+    private static final boolean PROTOCOL_LOG = false;
 
     /**
      * Connect to the given IP address using the port specified as part of the network parameters. Once construction
@@ -74,7 +75,7 @@ public class NetworkConnection {
 
         // When connecting, the remote peer sends us a version message with various bits of
         // useful data in it. We need to know the peer protocol version before we can talk to it.
-        VersionMessage ver = (VersionMessage) readMessage();
+        versionMessage = (VersionMessage) readMessage();
         // Now it's our turn ...
         writeMessage(MSG_VERSION, new VersionMessage(params));
         // Send an ACK message stating we accept the peers protocol version.
@@ -82,12 +83,13 @@ public class NetworkConnection {
         // And get one back ...
         readMessage();
         // Switch to the new protocol version.
-        int peerVersion = ver.clientVersion;
+        int peerVersion = versionMessage.clientVersion;
-        LOG("Connected to peer, version is " + peerVersion + ", services=" + Long.toHexString(
+        LOG(String.format("Connected to peer: version=%d, subVer='%s', services=0x%x, time=%s, blocks=%d",
-                ver.localServices) + ", time=" + new Date(ver.time.longValue() * 1000).toString());
+                peerVersion, versionMessage.subVer,
+                versionMessage.localServices, new Date(versionMessage.time * 1000).toString(), versionMessage.bestHeight));
         // BitCoinJ is a client mode implementation. That means there's not much point in us talking to other client
         // mode nodes because we can't download the data from them we need to find/verify transactions.
-        if (!ver.hasBlockChain())
+        if (!versionMessage.hasBlockChain())
             throw new ProtocolException("Peer does not have a copy of the block chain.");
         usesChecksumming = peerVersion >= 209;
         // Handshake is done!
@@ -198,9 +200,6 @@ public class NetworkConnection {
         if (size > Message.MAX_SIZE)
             throw new ProtocolException("Message size too large: " + size);
 
-        if (PROTOCOL_LOG)
-            LOG("Received " + size + " byte '" + command + "' command");
-
         // Old clients don't send the checksum.
         byte[] checksum = new byte[4];
         if (usesChecksumming) {
@@ -231,6 +230,9 @@ public class NetworkConnection {
             }
         }
 
+        if (PROTOCOL_LOG)
+            LOG("Received " + size + " byte '" + command + "' message: " + Utils.bytesToHexString(payloadBytes));
+
         try {
             Message message;
             if (command.equals(MSG_VERSION))
@@ -292,4 +294,9 @@ public class NetworkConnection {
         // TODO: Requiring "tag" here is redundant, the message object should know its own protocol tag.
         writeMessage(tag, message.bitcoinSerialize());
     }
+
+    /** Returns the version message received from the other end of the connection during the handshake. */
+    public VersionMessage getVersionMessage() {
+        return versionMessage;
+    }
 }

src/com/google/bitcoin/core/NetworkParameters.java

@@ -29,6 +29,11 @@ import java.math.BigInteger;
  * evolves there may be more. You can create your own as long as they don't conflict.
  */
 public class NetworkParameters implements Serializable {
+    /**
+     * The protocol version this library implements. A value of 31800 means 0.3.18.00.
+     */
+    public static final int PROTOCOL_VERSION = 31800;
+
     private static final long serialVersionUID = 2579833727976661964L;
 
     // TODO: Seed nodes and checkpoint values should be here as well.

src/com/google/bitcoin/core/Peer.java

@@ -106,9 +106,6 @@ public class Peer {
         }
     }
 
-    // This tracks whether we have received a block we could not connect to the chain in this session.
-    private boolean hasSeenUnconnectedBlock = false;
-
     private void processBlock(Block m) throws IOException {
         assert Thread.currentThread() == thread;
         try {
@@ -128,17 +125,13 @@ public class Peer {
             // Otherwise it's a block sent to us because the peer thought we needed it, so add it to the block chain.
             // This call will synchronize on blockChain.
             if (blockChain.add(m)) {
-                // The block was successfully linked into the chain.
+                // The block was successfully linked into the chain. Notify the user of our progress.
-                if (hasSeenUnconnectedBlock && blockChain.getUnconnectedBlock() == null) {
+                if (chainCompletionLatch != null) {
-                    // We cleared out our unconnected blocks. This likely means block chain download is "done" in the
+                    chainCompletionLatch.countDown();
-                    // sense that we were downloading blocks as part of the chained download,
+                    if (chainCompletionLatch.getCount() == 0) {
-                    // and there's no more to come. To some extent of course the download is never done.
+                        // All blocks fetched, so we don't need this anymore.
-                    LOG("Block chain download done.");
-                    if (chainCompletionLatch != null) {
-                        chainCompletionLatch.countDown();
                         chainCompletionLatch = null;
                     }
-                    hasSeenUnconnectedBlock = false;
                 }
             } else {
                 // This block is unconnected - we don't know how to get from it back to the genesis block yet. That
@@ -148,7 +141,6 @@ public class Peer {
                 // the others.
 
                 // TODO: Should actually request root of orphan chain here.
-                hasSeenUnconnectedBlock = true;
                 blockChainDownload(m.getHash());
             }
         } catch (VerificationException e) {
@@ -319,14 +311,20 @@ public class Peer {
     }
 
     /**
-     * Starts an asynchronous download of the block chain. Completion of the download is a somewhat vague concept in
+     * Starts an asynchronous download of the block chain. The chain download is deemed to be complete once we've
-     * BitCoin as the chain is constantly growing, but essentially we deem the download complete once we have
+     * downloaded the same number of blocks that the peer advertised having in its version handshake message.
-     * received the block that the peer told us was the head when we first started the download.
      *
-     * @return a {@link CountDownLatch} that can be used to wait until the chain download is "complete".
+     * @return a {@link CountDownLatch} that can be used to track progress and wait for completion.
      */
     public CountDownLatch startBlockChainDownload() throws IOException {
-        chainCompletionLatch = new CountDownLatch(1);
+        // Chain will overflow signed int blocks in ~41,000 years.
+        int chainHeight = (int) conn.getVersionMessage().bestHeight;
+        if (chainHeight <= 0) {
+            // This should not happen because we shouldn't have given the user a Peer that is to another client-mode
+            // node. If that happens it means the user overrode us somewhere.
+            throw new  RuntimeException("Peer does not have block chain");
+        }
+        chainCompletionLatch = new CountDownLatch(chainHeight);
         blockChainDownload(params.genesisBlock.getHash());
         return chainCompletionLatch;
     }

src/com/google/bitcoin/core/PeerAddress.java

@@ -36,9 +36,10 @@ public class PeerAddress extends Message {
     InetAddress addr;
     int port;
     BigInteger services;
+    long time;
 
-    public PeerAddress(NetworkParameters params, byte[] payload, int offset) throws ProtocolException {
+    public PeerAddress(NetworkParameters params, byte[] payload, int offset, int protocolVersion) throws ProtocolException {
-        super(params, payload, offset);
+        super(params, payload, offset, protocolVersion);
     }
     
     public PeerAddress(InetAddress addr, int port) {
@@ -72,7 +73,10 @@ public class PeerAddress extends Message {
         //   uint64 services   (flags determining what the node can do)
         //   16 bytes ip address
         //   2 bytes port num
-        long time = readUint32();
+        if (protocolVersion > 31402)
+            time = readUint32();
+        else
+            time = -1;
         services = readUint64();
         byte[] addrBytes = readBytes(16);
         try {

src/com/google/bitcoin/core/VersionMessage.java

@@ -25,22 +25,28 @@ import java.net.UnknownHostException;
 public class VersionMessage extends Message {
     private static final long serialVersionUID = 7313594258967483180L;
 
-    /**
-     * The protocol version this library implements. A value of 31800 means 0.3.18.00.
-     */
-    public static final int PROTOCOL_VERSION = 31800;
-
     /**
      * A services flag that denotes whether the peer has a copy of the block chain or not.
      */
     public static final int NODE_NETWORK = 1;
 
+    /** The version number of the protocol spoken. */
     public int clientVersion;
-    // Flags defining what the other side supports. Right now there's only one flag and it's
+    /** Flags defining what is supported. Right now {@link #NODE_NETWORK} is the only flag defined. */
-    // always set 1 by the official client, but we have to set it to zero as we don't store
-    // the block chain. In future there may be more services bits.
     public long localServices;
-    public BigInteger time;
+    /** What the other side believes the current time to be, in seconds. */
+    public long time;
+    /** What the other side believes the address of this program is. Not used. */
+    public PeerAddress myAddr;
+    /** What the other side believes their own address is. Not used. */
+    public PeerAddress theirAddr;
+    /**
+     * An additional string that today the official client sets to the empty string. We treat it as something like an
+     * HTTP User-Agent header.
+     */
+    public String subVer;
+    /** How many blocks are in the chain, according to the other side. */
+    public long bestHeight;
 
     public VersionMessage(NetworkParameters params, byte[] msg) throws ProtocolException {
         super(params, msg, 0);
@@ -48,43 +54,51 @@ public class VersionMessage extends Message {
 
     public VersionMessage(NetworkParameters params) {
         super(params);
-        clientVersion = PROTOCOL_VERSION;
+        clientVersion = NetworkParameters.PROTOCOL_VERSION;
         localServices = 0;
-        time = BigInteger.valueOf(System.currentTimeMillis() / 1000);
+        time = System.currentTimeMillis() / 1000;
+        // Note that the official client doesn't do anything with these, and finding out your own external IP address
+        // is kind of tricky anyway, so we just put nonsense here for now.
+        try {
+            myAddr = new PeerAddress(InetAddress.getLocalHost(), params.port);
+            theirAddr = new PeerAddress(InetAddress.getLocalHost(), params.port);
+        } catch (UnknownHostException e) {
+            throw new RuntimeException(e);  // Cannot happen.
+        }
+        subVer = "BitCoinJ 0.1.99";
+        bestHeight = 0;
     }
     
     @Override
     public void parse() throws ProtocolException {
-        // There is probably a more Java-ish way to do this.
         clientVersion = (int) readUint32();
         localServices = readUint64().longValue();
-        time = readUint64();
+        time = readUint64().longValue();
-        // The next fields are:
+        myAddr = new PeerAddress(params, bytes, cursor, 0);
-        //   CAddress my address
+        cursor += myAddr.getMessageSize();
-        //   CAddress their address
+        theirAddr = new PeerAddress(params, bytes, cursor, 0);
-        //   uint64 localHostNonce  (random data)
+        cursor += theirAddr.getMessageSize();
+        // uint64 localHostNonce  (random data)
+        // We don't care about the localhost nonce. It's used to detect connecting back to yourself in cases where
+        // there are NATs and proxies in the way. However we don't listen for inbound connections so it's irrelevant.
+        readUint64();
         //   string subVer  (currently "")
+        subVer = readStr();
         //   int bestHeight (size of known block chain).
-        //
+        bestHeight = readUint32();
-        // However, we don't care about these fields right now.
     }
     
-    
     @Override
     public void bitcoinSerializeToStream(OutputStream buf) throws IOException {
         Utils.uint32ToByteStreamLE(clientVersion, buf);
         Utils.uint32ToByteStreamLE(localServices, buf);
-        long ltime = time.longValue();
+        Utils.uint32ToByteStreamLE(time >> 32, buf);
-        Utils.uint32ToByteStreamLE(ltime >> 32, buf);
+        Utils.uint32ToByteStreamLE(time, buf);
-        Utils.uint32ToByteStreamLE(ltime, buf);
         try {
-            // Now there are two address structures. Note that the official client doesn't do anything with these, and
-            // finding out your own external IP address is kind of tricky anyway, so we just serialize nonsense here.
-
             // My address.
-            new PeerAddress(InetAddress.getLocalHost(), params.port).bitcoinSerializeToStream(buf);
+            myAddr.bitcoinSerializeToStream(buf);
             // Their address.
-            new PeerAddress(InetAddress.getLocalHost(), params.port).bitcoinSerializeToStream(buf);
+            theirAddr.bitcoinSerializeToStream(buf);
         } catch (UnknownHostException e) {
             throw new RuntimeException(e);  // Can't happen.
         } catch (IOException e) {
@@ -95,10 +109,12 @@ public class VersionMessage extends Message {
         // connections.
         Utils.uint32ToByteStreamLE(0, buf);
         Utils.uint32ToByteStreamLE(0, buf);
-        // Now comes an empty string.
+        // Now comes subVer.
-        buf.write(0);
+        byte[] subVerBytes = subVer.getBytes("UTF-8");
-        // Size of known block chain. Claim we never saw any blocks.
+        buf.write(new VarInt(subVerBytes.length).encode());
-        Utils.uint32ToByteStreamLE(0, buf);
+        buf.write(subVerBytes);
+        // Size of known block chain.
+        Utils.uint32ToByteStreamLE(bestHeight, buf);
     }
 
     /**

src/com/google/bitcoin/examples/PingService.java

@@ -22,6 +22,8 @@ import java.io.File;
 import java.io.IOException;
 import java.math.BigInteger;
 import java.net.InetAddress;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
 
 /**
  * PingService demonstrates basic usage of the library. It sits on the network and when it receives coins, simply
@@ -29,7 +31,7 @@ import java.net.InetAddress;
  */
 public class PingService {
     public static void main(String[] args) throws Exception {
-        final NetworkParameters params = NetworkParameters.prodNet();
+        final NetworkParameters params = NetworkParameters.testNet();
 
         // Try to read the wallet from storage, create a new one if not possible.
         Wallet wallet;
@@ -51,7 +53,6 @@ public class PingService {
         BlockChain chain = new BlockChain(params, wallet);
         final Peer peer = new Peer(params, conn, chain);
         peer.start();
-        peer.startBlockChainDownload().await();
 
         // We want to know when the balance changes.
         wallet.addEventListener(new WalletEventListener() {
@@ -82,6 +83,15 @@ public class PingService {
             }
         });
 
+        CountDownLatch progress = peer.startBlockChainDownload();
+        long max = progress.getCount();  // Racy but no big deal.
+        long current = max;
+        while (current > 0) {
+            double pct = 100.0 - (100.0 * (current / (double)max));
+            System.out.println(String.format("Chain download %d%% done", (int)pct));
+            progress.await(1, TimeUnit.SECONDS);
+            current = progress.getCount();
+        }
         System.out.println("Send coins to: " + key.toAddress(params).toString());
         System.out.println("Waiting for coins to arrive. Press Ctrl-C to quit.");
         // The peer thread keeps us alive until something kills the process.