Implement MDNS based discovery for local networks

README.md

@@ -29,6 +29,7 @@ Currently implemented properties:
 * bloom/[infini filtered](https://www.rasmuspagh.net/papers/infinifilter.pdf) blockstore
 * connect bitswap to kademlia for discovery, with a faster version with supplied peerids
 * configurable cid publishing function
+* mDNS peer discovery
 * Android compatibility
 * example serverless chat app using p2p http proxy for Android
 * interop tests with other implementations - https://github.com/libp2p/test-plans/
@@ -37,7 +38,6 @@ In the future we will add:
 * circuit-relay
 * dcutr (direct connection upgrade through relay)
 * AutoRelay
-* mDNS peer discovery
 * example iOS chat app
 * QUIC transport (and encryption and multiplexing)
 

src/main/java/org/peergos/EmbeddedIpfs.java

@@ -7,6 +7,7 @@
 import io.libp2p.core.crypto.*;
 import io.libp2p.core.multiformats.*;
 import io.libp2p.core.multistream.*;
+import io.libp2p.discovery.*;
 import io.libp2p.protocol.*;
 import org.peergos.blockstore.*;
 import org.peergos.blockstore.metadatadb.BlockMetadataStore;
@@ -26,6 +27,7 @@
 import org.peergos.protocol.ipns.*;
 import org.peergos.util.Logging;
 
+import java.net.*;
 import java.nio.file.*;
 import java.sql.Connection;
 import java.sql.DriverManager;
@@ -152,6 +154,18 @@ public void start() {
         LOG.info("Bootstrapping IPFS kademlia");
         dht.bootstrap(node);
         dht.startBootstrapThread(node);
+        InetAddress address = null;
+        MDnsDiscovery mdns = new MDnsDiscovery(node, "_ipfs-discovery._udp.local.", 60, address);
+        mdns.getNewPeerFoundListeners().add(peerInfo -> {
+            PeerId remote = PeerId.fromBase58(peerInfo.getPeerId().toBase58().substring(1)); // Not what's wrong with peerInfo, but this works
+            if (! remote.equals(node.getPeerId())) {
+                LOG.info(node.getPeerId() + " found local peer: " + peerInfo.getPeerId().toBase58() + ", addrs: " + peerInfo.getAddresses());
+                KademliaController ctr = dht.dial(node, remote, peerInfo.getAddresses().toArray(new Multiaddr[0])).getController().join();
+                ctr.closerPeers(node.getPeerId().getBytes()).join();
+            }
+            return null;
+        });
+        mdns.start();
 
         blockProvider.ifPresent(p -> p.start());
     }

src/test/java/org/peergos/EmbeddedIpfsTest.java

@@ -43,6 +43,25 @@ public void largeBlock() throws Exception {
         node2.stop();
     }
 
+    @Test
+    public void mdnsDiscovery() throws Exception {
+        EmbeddedIpfs node1 = build(Collections.emptyList(), List.of(new MultiAddress("/ip4/127.0.0.1/tcp/" + TestPorts.getPort())));
+        node1.start();
+        EmbeddedIpfs node2 = build(Collections.emptyList(), List.of(new MultiAddress("/ip4/127.0.0.1/tcp/" + TestPorts.getPort())));
+        node2.start();
+
+        Thread.sleep(5_000);
+        Cid block = node2.blockstore.put(new byte[1024], Cid.Codec.Raw).join();
+        PeerId peerId2 = node2.node.getPeerId();
+        List<HashedBlock> retrieved = ForkJoinPool.commonPool().submit(
+                () -> node1.getBlocks(List.of(new Want(block)), Set.of(peerId2), false))
+                .get(5, TimeUnit.SECONDS);
+        Assert.assertTrue(retrieved.size() == 1);
+
+        node1.stop();
+        node2.stop();
+    }
+
     @Test
     public void publishValue() throws Exception {
         EmbeddedIpfs node1 = build(BootstrapTest.BOOTSTRAP_NODES, List.of(new MultiAddress("/ip4/127.0.0.1/tcp/" + TestPorts.getPort())));