t.Fatal("should fail")
	} else if err.(*OpError).Err != ErrWriteToConnected {
		t.Fatalf("should fail as ErrWriteToConnected: %v", err)
	}
	if _, err = c.(*UnixConn).WriteTo(b, raddr); err == nil {
		t.Fatal("should fail")
	} else if err.(*OpError).Err != ErrWriteToConnected {
		t.Fatalf("should fail as ErrWriteToConnected: %v", err)
	}
	if _, _, err = c.(*UnixConn).WriteMsgUnix(b, nil, raddr); err == nil {

	if c.fd.isConnected {
		return 0, ErrWriteToConnected
	}
	if addr == nil {
		return 0, errMissingAddress
	}
	sa, err := addr.sockaddr(c.fd.family)
	if err != nil {
		return 0, err
	}
	return c.fd.writeTo(b, sa)
}

func (c *IPConn) writeMsg(b, oob []byte, addr *IPAddr) (n, oobn int, err error) {
	if c.fd.isConnected {
		return 0, 0, ErrWriteToConnected
	}
	if addr == nil {

		t.Fatal("should fail")
	}
	if err != nil && err.(*OpError).Err != ErrWriteToConnected {
		t.Fatalf("should fail as ErrWriteToConnected: %v", err)
	}
	_, err = c.(*UDPConn).WriteTo(b, ra)
	if err == nil {
		t.Fatal("should fail")
	}
	if err != nil && err.(*OpError).Err != ErrWriteToConnected {
		t.Fatalf("should fail as ErrWriteToConnected: %v", err)
	}
	_, err = c.Write(b)
	if err != nil {
		t.Fatal(err)

		addr = netip.AddrPortFrom(ip, uint16(sa.Port))
	}
	return
}

func (c *UDPConn) writeTo(b []byte, addr *UDPAddr) (int, error) {
	if c.fd.isConnected {
		return 0, ErrWriteToConnected
	}
	if addr == nil {
		return 0, errMissingAddress
	}

	switch c.fd.family {
	case syscall.AF_INET:
		sa, err := ipToSockaddrInet4(addr.IP, addr.Port)
		if err != nil {
			return 0, err

			addr = &UnixAddr{Name: sa.Name, Net: sotypeToNet(c.fd.sotype)}
		}
	}
	return
}

func (c *UnixConn) writeTo(b []byte, addr *UnixAddr) (int, error) {
	if c.fd.isConnected {
		return 0, ErrWriteToConnected
	}
	if addr == nil {
		return 0, errMissingAddress
	}
	if addr.Net != sotypeToNet(c.fd.sotype) {
		return 0, syscall.EAFNOSUPPORT
	}
	sa := &syscall.SockaddrUnix{Name: addr.Name}

		return nil
	case *os.SyscallError:
		nestedErr = err.Err
		goto third
	}
	switch nestedErr {
	case errCanceled, ErrClosed, errMissingAddress, errTimeout, os.ErrDeadlineExceeded, ErrWriteToConnected, io.ErrUnexpectedEOF:
		return nil
	}
	return fmt.Errorf("unexpected type on 2nd nested level: %T", nestedErr)

third:
	if isPlatformError(nestedErr) {
		return nil
	}

	// For connection setup and write operations.
	errMissingAddress = errors.New("missing address")

	// For both read and write operations.
	errCanceled         = canceledError{}
	ErrWriteToConnected = errors.New("use of WriteTo with pre-connected connection")
)

// canceledError lets us return the same error string we have always
// returned, while still being Is context.Canceled.
type canceledError struct{}

		{"Dialer.FallbackDelay", Field, 5},
		{"Dialer.KeepAlive", Field, 3},
		{"Dialer.LocalAddr", Field, 1},
		{"Dialer.Resolver", Field, 8},
		{"Dialer.Timeout", Field, 1},
		{"ErrClosed", Var, 16},
		{"ErrWriteToConnected", Var, 0},
		{"Error", Type, 0},
		{"FileConn", Func, 0},
		{"FileListener", Func, 0},
		{"FilePacketConn", Func, 0},
		{"FlagBroadcast", Const, 0},
		{"FlagLoopback", Const, 0},

pkg net, type UnixAddr struct, Name string
pkg net, type UnixAddr struct, Net string
pkg net, type UnixConn struct
pkg net, type UnixListener struct
pkg net, type UnknownNetworkError string
pkg net, var ErrWriteToConnected error
pkg net, var IPv4allrouter IP
pkg net, var IPv4allsys IP
pkg net, var IPv4bcast IP
pkg net, var IPv4zero IP
pkg net, var IPv6interfacelocalallnodes IP
pkg net, var IPv6linklocalallnodes IP