Thread: Searching User Currently Logged On

Hi, like every time before , I have a problem...
I am on a network and given a username (Login User Name).
How can I determine that wether that user is logged on network or not?
If logged on than on which workstation (name) is the user logged on...

Assuming all workstations have win NT 4.0 and I do not have adminisitrative rights!!!!

Mention any c functions that are required (with lots of lots of info )


Thanx....

I heard from some one that netbios may help.
How can I get netbios from a pc...

I suspected that net send uses net-bios names. With a little research and a lot of trial and error, I created a function. It would be helpful, in the future, if you posted a link to other threads where you have asked the same question so that we don't have to start from scratch.

Code:

#include <winsock2.h>
#include <windows.h>
#include <stdio.h>
#include <nb30.h>

#if defined(_MSC_VER)
#pragma comment(lib, "wsock32.lib")
#pragma comment(lib, "Netapi32.lib")
#endif

/*
 * This function attempts to find a logged-on user on the local network.
 * It uses net-bios names registered by the messenger service to perform the lookup.
 * 
 * Requirements:
 *   - The messenger service must be running on the target machines.
 *   - The user name must not contain non-ascii characters or be longer than 16 characters.
 *
 * Paramaters:
 *   - szUser:     The user name to look up.
 *   - szMachine:  A buffer in which to return the net-bios machine name where
 *                 the user is logged-on. This buffer must be at least NCBNAMSZ + 1
 *                 characters in size. Upon return the machine name can be passed
 *                 to the gethostbyname function to obtain its IP address.
 *   - cchMachine: The size of the szMachine buffer.
 *
 * Returns:
 *   A non-zero value upon success. Zero on failure. GetLastError() can NOT be called
 *   to obtain a reason code.
 *
 * Note:
 *   This function is intended for use when you don't have administrator privileges
 *   on the target machines. If you do, use NetServerEnum and NetWkstaUserEnum instead.
 */
BOOL FindUserOnNetwork(LPCSTR szUser, LPSTR szMachine, UINT cchMachine)
{
	NCB  ncb;
	BYTE buf[sizeof (ADAPTER_STATUS) + (255 * sizeof (NAME_BUFFER))];
	ADAPTER_STATUS* pStatus = (ADAPTER_STATUS*) buf;
	NAME_BUFFER*    pNames  = (NAME_BUFFER*) (pStatus + 1);
	int             cchUser = lstrlenA(szUser);
	int             i       = 0;
	BOOL            bFound  = FALSE;

	if (cchMachine > 0)
		szMachine[0] = '\0';

	/* Check arguments. */
	if (cchUser > NCBNAMSZ ||
	    cchMachine < NCBNAMSZ + 1)
		return FALSE;

	/* Net-Bios Reset. */
	ZeroMemory(&ncb, sizeof(ncb));
	ncb.ncb_command  = NCBRESET;
	ncb.ncb_lana_num = 0;
	Netbios(&ncb);

	if (NRC_GOODRET != ncb.ncb_retcode)
		return FALSE;

	ZeroMemory(&ncb, sizeof(ncb));

	/* Make a space padded net-bios name. */
	memset(ncb.ncb_callname, ' ',    NCBNAMSZ);
	memcpy(ncb.ncb_callname, szUser, cchUser);

	/* The last character in a net-bios name registered
	 * by the messenger service is 0x3. */
	ncb.ncb_callname[NCBNAMSZ - 1] = 0x03;

	/* Retrieve the net-bios adapter status for the given net-bios name. */
	ncb.ncb_command  = NCBASTAT;
	ncb.ncb_lana_num = 0;
	ncb.ncb_buffer   = buf;
	ncb.ncb_length   = sizeof(buf);
	Netbios(&ncb);

	if (NRC_GOODRET != ncb.ncb_retcode)
		return FALSE;

	for (i = 0; i < pStatus->name_count; i++)
	{
		if (!(pNames[i].name_flags & GROUP_NAME) &&
		     (pNames[i].name[NCBNAMSZ - 1] == 0x00))
		{
			lstrcpyA(szMachine, pNames[i].name);
			bFound = TRUE;
		}
#if defined(DEBUG)
		printf("Flags: 0x%02x\nType:  0x%02x\nName:  %.16s\n\n",
		        pNames[i].name_flags, pNames[i].name[15], pNames[i].name);
#endif
	}

	/* Remove trailing spaces. */
	for (i = lstrlenA(szMachine) - 1; i >= 0 && szMachine[i] == ' '; i--)
		szMachine[i] = '\0';

	return bFound;
}

int main(void)
{
	WSADATA  wsad;
	CHAR     buf[NCBNAMSZ + 1];
	struct hostent* host;
	struct in_addr  addr;

	FindUserOnNetwork("USER1", buf, sizeof(buf));
	printf("Machine name: %s\n", buf);

	WSAStartup(MAKEWORD(2, 2), &wsad);

	host = gethostbyname(buf);
	if (host != NULL)
	{
		memcpy(&addr.S_un.S_addr, host->h_addr_list[0], sizeof(ULONG));
		printf("IP Address: %s\n", inet_ntoa(addr));
	}

	getchar();
	return 0;
}

Wow great friend, and you know what I found the reverse .i.e. finding user logged on a machine by giving machine name using net bios.