callbacks.go | 7 +++++++
 peerconn.go  | 3 +++

diff --git a/callbacks.go b/callbacks.go
index fa9fea5bea3d3c824ee04467da51c1ee781453b8..f78c58545e4d41c75daf3aa8d7cc57e957d858a0 100644
--- a/callbacks.go
+++ b/callbacks.go
@@ -18,4 +18,11 @@ 	PeerConnClosed        func(*PeerConn)
 
 	// Provides secret keys to be tried against incoming encrypted connections.
 	ReceiveEncryptedHandshakeSkeys mse.SecretKeyIter
+
+	ReceivedUsefulData []func(ReceivedUsefulDataEvent)
+}
+
+type ReceivedUsefulDataEvent struct {
+	Peer    *Peer
+	Message *pp.Message
 }
diff --git a/peerconn.go b/peerconn.go
index 4fcb4f3d772594233336dbd53418274fab7c664d..25d29b340469fefce107d99ef68c46640b615860 100644
--- a/peerconn.go
+++ b/peerconn.go
@@ -1378,6 +1378,9 @@ 	piece := &t.pieces[req.Index]
 
 	c.allStats(add(1, func(cs *ConnStats) *Count { return &cs.ChunksReadUseful }))
 	c.allStats(add(int64(len(msg.Piece)), func(cs *ConnStats) *Count { return &cs.BytesReadUsefulData }))
+	for _, f := range c.t.cl.config.Callbacks.ReceivedUsefulData {
+		f(ReceivedUsefulDataEvent{c, msg})
+	}
 	c.lastUsefulChunkReceived = time.Now()
 	// if t.fastestPeer != c {
 	// log.Printf("setting fastest connection %p", c)