if want, have := "Produced ", buf.String(); have != want {
		t.Errorf("unexpected server reply %q, want %q", have, want)
	}

	for err := range errc {
		t.Error(err)
	}
}

func TestSendfileSeeked(t *testing.T) {
	ln := newLocalListener(t, "tcp")
	defer ln.Close()

	const seekTo = 65 << 10
	const sendSize = 10 << 10

	errc := make(chan error, 1)
	go func(ln Listener) {