diff --git a/udp.go b/udp.go
index 02dbfda..375a068 100644
--- a/udp.go
+++ b/udp.go
@@ -20,18 +20,18 @@ type UDPConn struct {
 }
 
 func (s *UDPConn) ReadFrom(b []byte) (int, net.Addr, error) {
-	_, _, err := s.PacketConn.ReadFrom(b)
+	nr, _, err := s.PacketConn.ReadFrom(b)
 	if err != nil {
 		return 0, nil, err
 	}
 
-	datagram, err := NewDatagramFrom(bytes.NewReader(b))
+	datagram, err := NewDatagramFrom(bytes.NewReader(b[:nr]))
 	if err != nil {
 		return 0, nil, err
 	}
 
-	n := copy(b, datagram.Data)
-	return n, AddrFromSocks(datagram.ATYP, datagram.DstAddr, datagram.DstPort), nil
+	nc := copy(b, datagram.Data)
+	return nc, AddrFromSocks(datagram.ATYP, datagram.DstAddr, datagram.DstPort), nil
 }
 
 func (s *UDPConn) Read(b []byte) (int, error) {