Implement Net Send

Problem/Question/Abstract:

How to implement netsend?

Answer:

function NetSend(dest, Source, Msg: string): Longint; overload;
type
  TNetMessageBufferSendFunction = function(servername, msgname, fromname: PWideChar;
    buf: PWideChar; buflen: Cardinal): Longint; stdcall;
var
  NetMessageBufferSend: TNetMessageBufferSendFunction;
  SourceWideChar: PWideChar;
  DestWideChar: PWideChar;
  MessagetextWideChar: PWideChar;
  Handle: THandle;
begin
  Handle := LoadLibrary('NETAPI32.DLL');
  if Handle = 0 then
  begin
    Result := GetLastError;
    Exit;
  end;
  @NetMessageBufferSend := GetProcAddress(Handle, 'NetMessageBufferSend');
  if @NetMessageBufferSend = nil then
  begin
    Result := GetLastError;
    Exit;
  end;

  MessagetextWideChar := nil;
  SourceWideChar := nil;
  DestWideChar := nil;

  try
    GetMem(MessagetextWideChar, Length(Msg) * SizeOf(WideChar) + 1);
    GetMem(DestWideChar, 20 * SizeOf(WideChar) + 1);
    StringToWideChar(Msg, MessagetextWideChar, Length(Msg) * SizeOf(WideChar) + 1);
    StringToWideChar(Dest, DestWideChar, 20 * SizeOf(WideChar) + 1);

    if Source = '' then
      Result := NetMessageBufferSend(nil, DestWideChar, nil,
        MessagetextWideChar, Length(Msg) * SizeOf(WideChar) + 1)
    else
    begin
      GetMem(SourceWideChar, 20 * SizeOf(WideChar) + 1);
      StringToWideChar(Source, SourceWideChar, 20 * SizeOf(WideChar) + 1);
      Result := NetMessageBufferSend(nil, DestWideChar, SourceWideChar,
        MessagetextWideChar, Length(Msg) * SizeOf(WideChar) + 1);
      FreeMem(SourceWideChar);
    end;
  finally
    FreeMem(MessagetextWideChar);
    FreeLibrary(Handle);
  end;
end;

function NetSend(Dest, Msg: string): Longint; overload;
begin
  Result := NetSend(Dest, '', Msg);
end;

function NetSend(Msg: string): Longint; overload;
begin
  Result := NetSend('', '', Msg);
end;

Example:

procedure TForm1.Button1Click(Sender: TObject);
const
  NERR_BASE = 2100;
  NERR_NameNotFound = NERR_BASE + 173;
  NERR_NetworkError = NERR_BASE + 36;
  NERR_Success = 0;
var
  Res: Longint;
  sMsg: string;
begin
  Res := NetSend('LoginName', 'Your Message...');
  case Res of
    ERROR_ACCESS_DENIED: sMsg :=
      'user does not have access to the requested information.';
    ERROR_INVALID_PARAMETER: sMsg := 'The specified parameter is invalid.';
    ERROR_NOT_SUPPORTED: sMsg := 'This network request is not supported.';
    NERR_NameNotFound: sMsg := 'The user name could not be found.';
    NERR_NetworkError: sMsg := 'A general failure occurred in the network hardware.';
    NERR_Success: sMsg := 'Message sent!';
  end;
  ShowMessage(sMsg);
end;