Simplify the utpSocket interface definition

utp.go

@@ -3,21 +3,16 @@ package torrent
 import (
 	"context"
 	"net"
-	"time"
 )
 
 // Abstracts the utp Socket, so the implementation can be selected from
 // different packages.
 type utpSocket interface {
+	net.PacketConn
+	// net.Listener, but we can't have duplicate Close.
 	Accept() (net.Conn, error)
 	Addr() net.Addr
-	Close() error
-	LocalAddr() net.Addr
-	ReadFrom([]byte) (int, net.Addr, error)
-	SetDeadline(time.Time) error
-	SetWriteDeadline(time.Time) error
-	SetReadDeadline(time.Time) error
-	WriteTo([]byte, net.Addr) (int, error)
+	// net.Dialer but there's no interface.
 	DialContext(ctx context.Context, addr string) (net.Conn, error)
 	Dial(addr string) (net.Conn, error)
 }