n, oobn, flags, addr, err = c.readMsg(b, oob)
	if err != nil {
		err = &OpError{Op: "read", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
	}
	return
}

// WriteToUDP acts like WriteTo but takes a UDPAddr.
func (c *UDPConn) WriteToUDP(b []byte, addr *UDPAddr) (int, error) {
	if !c.ok() {
		return 0, syscall.EINVAL
	}
	n, err := c.writeTo(b, addr)
	if err != nil {

		t.Fatal(err)
	}
	defer c.Close()

	ra, err := ResolveUDPAddr("udp", raddr)
	if err != nil {
		t.Fatal(err)
	}

	b := []byte("CONNECTED-MODE SOCKET")
	_, err = c.(*UDPConn).WriteToUDP(b, ra)
	if err == nil {
		t.Fatal("should fail")
	}
	if err != nil && err.(*OpError).Err != ErrWriteToConnected {
		t.Fatalf("should fail as ErrWriteToConnected: %v", err)
	}