diff --git a/core/src/main/groovy/com/muwire/core/connection/ConnectionManager.groovy b/core/src/main/groovy/com/muwire/core/connection/ConnectionManager.groovy
index 0f9d6144..7af84855 100644
--- a/core/src/main/groovy/com/muwire/core/connection/ConnectionManager.groovy
+++ b/core/src/main/groovy/com/muwire/core/connection/ConnectionManager.groovy
@@ -21,5 +21,5 @@ abstract class ConnectionManager {
 	
 	abstract void drop(Destination d)
 	
-	abstract boolean hasConnection()
+	abstract Collection<Connection> getConnections()
 }
diff --git a/core/src/main/groovy/com/muwire/core/connection/LeafConnectionManager.groovy b/core/src/main/groovy/com/muwire/core/connection/LeafConnectionManager.groovy
index 6ce4babc..78cfd7d2 100644
--- a/core/src/main/groovy/com/muwire/core/connection/LeafConnectionManager.groovy
+++ b/core/src/main/groovy/com/muwire/core/connection/LeafConnectionManager.groovy
@@ -20,8 +20,8 @@ class LeafConnectionManager extends ConnectionManager {
 	}
 
 	@Override
-	public boolean hasConnection() {
+	public Collection<Connection> getConnections() {
 		// TODO implement
-		false
+		[]
 	}
 }
diff --git a/core/src/main/groovy/com/muwire/core/connection/UltrapeerConnectionManager.groovy b/core/src/main/groovy/com/muwire/core/connection/UltrapeerConnectionManager.groovy
index cc760f20..a6b2ee3b 100644
--- a/core/src/main/groovy/com/muwire/core/connection/UltrapeerConnectionManager.groovy
+++ b/core/src/main/groovy/com/muwire/core/connection/UltrapeerConnectionManager.groovy
@@ -1,5 +1,7 @@
 package com.muwire.core.connection
 
+import java.util.Collection
+
 import com.muwire.core.EventBus
 
 import net.i2p.data.Destination
@@ -20,8 +22,18 @@ class UltrapeerConnectionManager extends ConnectionManager {
 	}
 
 	@Override
-	public boolean hasConnection() {
-		// TODO: implement
-		false
+	public Collection<Connection> getConnections() {
+		// TODO implement
+		[]
+	}
+	
+	boolean hasLeafSlots() {
+		// TODO implement
+		true
+	}
+	
+	boolean hasPeerSlots() {
+		// TODO implement
+		true
 	}
 }
diff --git a/core/src/main/groovy/com/muwire/core/hostcache/CacheClient.groovy b/core/src/main/groovy/com/muwire/core/hostcache/CacheClient.groovy
index 36d8f120..340e96e8 100644
--- a/core/src/main/groovy/com/muwire/core/hostcache/CacheClient.groovy
+++ b/core/src/main/groovy/com/muwire/core/hostcache/CacheClient.groovy
@@ -3,17 +3,23 @@ package com.muwire.core.hostcache
 import com.muwire.core.EventBus
 import com.muwire.core.MuWireSettings
 import com.muwire.core.connection.ConnectionManager
+import com.muwire.core.connection.UltrapeerConnectionManager
 
 import groovy.json.JsonOutput
+import groovy.json.JsonSlurper
 import groovy.util.logging.Log
 import net.i2p.client.I2PSession
 import net.i2p.client.I2PSessionMuxedListener
 import net.i2p.client.SendMessageOptions
+import net.i2p.client.datagram.I2PDatagramDissector
 import net.i2p.client.datagram.I2PDatagramMaker
+import net.i2p.data.Destination
 
 @Log
 class CacheClient {
 	
+	private static final int CRAWLER_RETURN = 10
+	
 	final EventBus eventBus
 	final HostCache cache
 	final ConnectionManager manager
@@ -42,7 +48,7 @@ class CacheClient {
 	}
 	
 	private void queryIfNeeded() {
-		if (manager.hasConnection())
+		if (!manager.getConnections().isEmpty())
 			return
 		if (!cache.getHosts(1).isEmpty())
 			return
@@ -62,6 +68,8 @@ class CacheClient {
 	}
 	
 	class Listener implements I2PSessionMuxedListener {
+		
+		private final JsonSlurper slurper = new JsonSlurper()
 
 		@Override
 		public void messageAvailable(I2PSession session, int msgId, long size) {
@@ -69,8 +77,35 @@ class CacheClient {
 
 		@Override
 		public void messageAvailable(I2PSession session, int msgId, long size, int proto, int fromport, int toport) {
-			// TODO Auto-generated method stub
 			
+			if (proto != I2PSession.PROTO_DATAGRAM) {
+				log.warning "Received unexpected protocol $proto"
+				return
+			}
+			
+			def payload = session.receiveMessage(msgId)
+			def dissector = new I2PDatagramDissector()
+			try {
+				dissector.loadI2PDatagram(payload)
+				def sender = dissector.getSender()
+				log.info("Received something from ${sender.toBase32()}")
+				
+				payload = dissector.getPayload()
+				payload = slurper.parse(payload)
+				
+				if (payload.type == null) {
+					log.warning("type missing")
+					return
+				}
+				
+				switch(payload.type) {
+					case "Pong" : handlePong(sender, payload); break
+					case "CrawlerPing": handleCrawlerPing(session, sender, payload); break
+					default : log.warning("unknown type ${payload.type}")
+				}
+			} catch (Exception e) {
+				log.warning("Invalid datagram $e")
+			}
 		}
 
 		@Override
@@ -88,5 +123,64 @@ class CacheClient {
 		}
 		
 	}
+	
+	private void handlePong(Destination from, def pong) {
+		if (!CacheServers.isRegistered(from)) {
+			log.warning("received pong from non-registered destination")
+			return
+		}
+		
+		if (pong.pongs == null) {
+			log.warning("malformed pong - no pongs")
+			return
+		}
+		
+		pong.pongs.asList().each { eventBus.publish(new HostDiscoveredEvent(destination: new Destination(it))) }
+		
+	}
+	
+	private void handleCrawlerPing(I2PSession session, Destination from, def ping) {
+		if (settings.isLeaf()) {
+			log.warning("Received crawler ping but I'm a leaf")
+			return
+		}
+		
+		switch(settings.getCrawlerResponse()) {
+			case CrawlerResponse.NONE:
+				log.info("Responding to crawlers is disabled by user")
+				break
+			case CrawlerResponse.ALL:
+				respondToCrawler(session, from, ping)
+				break;
+			case CrawlerResponse.REGISTERED:
+				if (CacheServers.isRegistered(from))
+					respondToCrawler(session, from, ping)
+				else
+					log.warning("Ignoring crawler ping from non-registered crawler")
+				break
+		}
+	}
+	
+	private void respondToCrawler(I2PSession session, Destination from, def ping) {
+		log.info "responding to crawler ping"
+		
+		def neighbors = manager.getConnections().collect { c -> c.remoteSide.toBase64() }
+		Collections.shuffle(neighbors)
+		if (neighbors.size() > CRAWLER_RETURN)
+			neighbors = neighbors[0..CRAWLER_RETURN - 1]
+		
+		def upManager = (UltrapeerConnectionManager) manager;
+		def pong = [:]
+		pong.peers = neighbors
+		pong.uuid = ping.uuid
+		pong.version = 1
+		pong.leafSlots = upManager.hasLeafSlots()
+		pong.peerSlots = upManager.hasPeerSlots()
+		pong = JsonOutput.toJson(pong)
+		
+		def maker = new I2PDatagramMaker(session)
+		pong = maker.makeI2PDatagram(pong.bytes)
+		session.sendMessage(from, pong, I2PSession.PROTO_DATAGRAM, 0, 0)
+	}
 
 }