sendto

// WS2_32.dll
#include <windows.h>

INT sendto(
    SOCKET s,
    LPCSTR buf,
    INT len,
    INT flags,
    const SOCKADDR* to,
    INT tolen
);

<DllImport("WS2_32.dll", SetLastError:=True, ExactSpelling:=True)>
Public Shared Function sendto(
    s As UIntPtr,   ' SOCKET
    <MarshalAs(UnmanagedType.LPStr)> buf As String,   ' LPCSTR
    len As Integer,   ' INT
    flags As Integer,   ' INT
    [to] As IntPtr,   ' SOCKADDR*
    tolen As Integer   ' INT
) As Integer
End Function

' s : SOCKET
' buf : LPCSTR
' len : INT
' flags : INT
' to : SOCKADDR*
' tolen : INT
Declare PtrSafe Function sendto Lib "ws2_32" ( _
    ByVal s As LongPtr, _
    ByVal buf As String, _
    ByVal len As Long, _
    ByVal flags As Long, _
    ByVal to As LongPtr, _
    ByVal tolen As Long) As Long
' VBA7前提(PtrSafe)。32bit Office では LongPtr→Long。Integer=16bit / Long=32bit / LongLong=64bit。

import ctypes
from ctypes import wintypes

sendto = ctypes.windll.ws2_32.sendto
sendto.restype = ctypes.c_int
sendto.argtypes = [
    ctypes.c_size_t,  # s : SOCKET
    wintypes.LPCSTR,  # buf : LPCSTR
    ctypes.c_int,  # len : INT
    ctypes.c_int,  # flags : INT
    ctypes.c_void_p,  # to : SOCKADDR*
    ctypes.c_int,  # tolen : INT
]
# GetLastError: use ctypes.GetLastError() (or ctypes.WinDLL(use_last_error=True))

require 'fiddle'
require 'fiddle/import'

lib = Fiddle.dlopen('WS2_32.dll')
sendto = Fiddle::Function.new(
  lib['sendto'],
  [
    Fiddle::TYPE_UINTPTR_T,  # s : SOCKET
    Fiddle::TYPE_VOIDP,  # buf : LPCSTR
    Fiddle::TYPE_INT,  # len : INT
    Fiddle::TYPE_INT,  # flags : INT
    Fiddle::TYPE_VOIDP,  # to : SOCKADDR*
    Fiddle::TYPE_INT,  # tolen : INT
  ],
  Fiddle::TYPE_INT)

#[link(name = "ws2_32")]
extern "system" {
    fn sendto(
        s: usize,  // SOCKET
        buf: *const u8,  // LPCSTR
        len: i32,  // INT
        flags: i32,  // INT
        to: *const SOCKADDR,  // SOCKADDR*
        tolen: i32  // INT
    ) -> i32;
}
// crates: windows-sys provides ready-made bindings for this API.

$sig = @"
[DllImport("WS2_32.dll", SetLastError = true)]
public static extern int sendto(UIntPtr s, [MarshalAs(UnmanagedType.LPStr)] string buf, int len, int flags, IntPtr to, int tolen);
"@
$api = Add-Type -MemberDefinition $sig -Name 'WS2_32_sendto' -Namespace Win32 -PassThru
# $api::sendto(s, buf, len, flags, to, tolen)

#uselib "WS2_32.dll"
#func global sendto "sendto" sptr, sptr, sptr, sptr, sptr, sptr
; sendto s, buf, len, flags, varptr(to), tolen   ; 戻り値は stat
; s : SOCKET -> "sptr"
; buf : LPCSTR -> "sptr"
; len : INT -> "sptr"
; flags : INT -> "sptr"
; to : SOCKADDR* -> "sptr"
; tolen : INT -> "sptr"
; ※HSP3.7は #func のため戻り値はシステム変数 stat に格納されます。

#uselib "WS2_32.dll"
#cfunc global sendto "sendto" sptr, str, int, int, var, int
; res = sendto(s, buf, len, flags, to, tolen)
; s : SOCKET -> "sptr"
; buf : LPCSTR -> "str"
; len : INT -> "int"
; flags : INT -> "int"
; to : SOCKADDR* -> "var"
; tolen : INT -> "int"
; ※出力/バッファ引数は var 方式(変数を直接渡す)。varptr 方式にも切替可。

; INT sendto(SOCKET s, LPCSTR buf, INT len, INT flags, SOCKADDR* to, INT tolen)
#uselib "WS2_32.dll"
#cfunc global sendto "sendto" intptr, str, int, int, var, int
; res = sendto(s, buf, len, flags, to, tolen)
; s : SOCKET -> "intptr"
; buf : LPCSTR -> "str"
; len : INT -> "int"
; flags : INT -> "int"
; to : SOCKADDR* -> "var"
; tolen : INT -> "int"
; ※出力/バッファ引数は var 方式(変数を直接渡す)。varptr 方式にも切替可。

import (
	"golang.org/x/sys/windows"
	"unsafe"
)

var (
	ws2_32 = windows.NewLazySystemDLL("WS2_32.dll")
	procsendto = ws2_32.NewProc("sendto")
)

// s (SOCKET), buf (LPCSTR), len (INT), flags (INT), to (SOCKADDR*), tolen (INT)
r1, _, err := procsendto.Call(
	uintptr(s),
	uintptr(unsafe.Pointer(windows.BytePtrFromString(buf))),
	uintptr(len),
	uintptr(flags),
	uintptr(to),
	uintptr(tolen),
)
_ = err  // syscall.Errno (valid when the call sets last-error)
_ = r1   // INT

function sendto(
  s: NativeUInt;   // SOCKET
  buf: PAnsiChar;   // LPCSTR
  len: Integer;   // INT
  flags: Integer;   // INT
  to: Pointer;   // SOCKADDR*
  tolen: Integer   // INT
): Integer; stdcall;
  external 'WS2_32.dll' name 'sendto';

result := DllCall("WS2_32\sendto"
    , "UPtr", s   ; SOCKET
    , "AStr", buf   ; LPCSTR
    , "Int", len   ; INT
    , "Int", flags   ; INT
    , "Ptr", to   ; SOCKADDR*
    , "Int", tolen   ; INT
    , "Int")   ; return: INT

●sendto(s, buf, len, flags, to, tolen) = DLL("WS2_32.dll", "int sendto(int, char*, int, int, void*, int)")
# 呼び出し: sendto(s, buf, len, flags, to, tolen)
# s : SOCKET -> "int"
# buf : LPCSTR -> "char*"
# len : INT -> "int"
# flags : INT -> "int"
# to : SOCKADDR* -> "void*"
# tolen : INT -> "int"
# なでしこ1は32bit・ANSI(Shift_JIS)。文字列=char*(ANSI)、ポインタ/ハンドル=void*(4byte)。