diff --git a/kcp.go b/kcp.go
index 2c0a105..c5d6603 100644
--- a/kcp.go
+++ b/kcp.go
@@ -230,19 +230,21 @@ func (kcp *KCP) PeekSize() (length int) {
 	return
 }
 
-// Recv is user/upper level recv: returns size, returns below zero for EAGAIN
+// Receive data from kcp state machine
+//
+// Return number of bytes read.
+//
+// Return -1 when there is no readable data.
+//
+// Return -2 if len(buffer) is smaller than kcp.PeekSize().
 func (kcp *KCP) Recv(buffer []byte) (n int) {
-	if len(kcp.rcv_queue) == 0 {
+	peeksize := kcp.PeekSize()
+	if peeksize < 0 {
 		return -1
 	}
 
-	peeksize := kcp.PeekSize()
-	if peeksize < 0 {
-		return -2
-	}
-
 	if peeksize > len(buffer) {
-		return -3
+		return -2
 	}
 
 	var fast_recover bool
diff --git a/sess.go b/sess.go
index 2d45548..9935d5f 100644
--- a/sess.go
+++ b/sess.go
@@ -1,4 +1,4 @@
-// Package kcp-go is a reliable-udp library for golang.
+// Package kcp-go is a Reliable-UDP library for golang.
 //
 // This library intents to provide a smooth, resilient, ordered,
 // error-checked and anonymous delivery of streams over UDP packets.
@@ -430,7 +430,9 @@ func (s *UDPSession) SetACKNoDelay(nodelay bool) {
 	s.ackNoDelay = nodelay
 }
 
-// SetDUP duplicates udp packets for kcp output, for testing purpose only
+// (deprecated)
+//
+// SetDUP duplicates udp packets for kcp output.
 func (s *UDPSession) SetDUP(dup int) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
@@ -930,10 +932,16 @@ func ServeConn(block BlockCrypt, dataShards, parityShards int, conn net.PacketCo
 	return l, nil
 }
 
-// Dial connects to the remote address "raddr" on the network "udp"
+// Dial connects to the remote address "raddr" on the network "udp" without encryption and FEC
 func Dial(raddr string) (net.Conn, error) { return DialWithOptions(raddr, nil, 0, 0) }
 
 // DialWithOptions connects to the remote address "raddr" on the network "udp" with packet encryption
+//
+// 'block' is the block encryption algorithm to encrypt packets.
+//
+// 'dataShards', 'parityShards' specifiy how many parity packets will be generated following the data packets.
+//
+// Check https://github.com/klauspost/reedsolomon for details
 func DialWithOptions(raddr string, block BlockCrypt, dataShards, parityShards int) (*UDPSession, error) {
 	// network type detection
 	udpaddr, err := net.ResolveUDPAddr("udp", raddr)