c.Close()
				t.Fatalf("%s succeeded, want error", op)
			}
			if perr := parseDialError(err); perr != nil {
				t.Fatal(perr)
			}
			operr := err.(*OpError).Err
			aerr, ok := operr.(*AddrError)
			if !ok {
				t.Fatalf("OpError.Err is %T, want *AddrError", operr)
			}
			want := tt.lit
			if tt.lit == "" {
				want = tt.addr.IP.String()
			}
			if aerr.Addr != want {

		}
		return nil, nil
	})
	defer sw.Set(socktest.FilterAccept, nil)

	operr := make(chan error, 1)
	handler := func(ls *localServer, ln Listener) {
		defer close(operr)
		c, err := ln.Accept()
		if err != nil {
			if perr := parseAcceptError(err); perr != nil {
				operr <- perr
			}
			operr <- err
			return
		}
		c.Close()
	}
	ls := newLocalServer(t, "tcp")

	if err != nil {
		err = &OpError{Op: "read", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
	}
	return n, addr, err
}

// ReadFrom implements the [PacketConn] ReadFrom method.
func (c *UnixConn) ReadFrom(b []byte) (int, Addr, error) {
	if !c.ok() {
		return 0, nil, syscall.EINVAL
	}
	n, addr, err := c.readFrom(b)
	if err != nil {

	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 {

	if err != nil && err != io.EOF {
		err = &OpError{Op: "readfrom", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
	}
	return n, err
}

// WriteTo implements the io.WriterTo WriteTo method.
func (c *TCPConn) WriteTo(w io.Writer) (int64, error) {
	if !c.ok() {
		return 0, syscall.EINVAL
	}
	n, err := c.writeTo(w)
	if err != nil && err != io.EOF {

}

// DialContext connects to the provided address on the provided
// network.
//
// The returned error value may be a net.OpError. When the Op field of
// net.OpError contains "socks", the Source field contains a proxy
// server address and the Addr field contains a command target
// address.
//
// See func Dial of the net package of standard library for a

	if err != nil && err != io.EOF {
		err = &OpError{Op: "read", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
	}
	return n, err
}

// Write implements the Conn Write method.
func (c *conn) Write(b []byte) (int, error) {
	if !c.ok() {
		return 0, syscall.EINVAL
	}
	n, err := c.fd.Write(b)
	if err != nil {

	case *UnixAddr:
		la, _ := la.(*UnixAddr)
		c, err = sd.dialUnix(ctx, la, ra)
	default:
		return nil, &OpError{Op: "dial", Net: sd.network, Source: la, Addr: ra, Err: &AddrError{Err: "unexpected address type", Addr: sd.address}}
	}
	if err != nil {
		return nil, &OpError{Op: "dial", Net: sd.network, Source: la, Addr: ra, Err: err} // c is non-nil interface containing nil pointer
	}
	return c, nil
}

	"io"
	"os"
	"os/exec"
	"regexp"
	"slices"
	"strings"
	"syscall"
	"testing"
	"time"
)

func toErrno(err error) (syscall.Errno, bool) {
	operr, ok := err.(*OpError)
	if !ok {
		return 0, false
	}
	syserr, ok := operr.Err.(*os.SyscallError)
	if !ok {
		return 0, false
	}
	errno, ok := syserr.Err.(syscall.Errno)
	if !ok {
		return 0, false
	}
	return errno, true
}

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