I was trying to fetch Mac addrs of all the devices present in WiFi environment(whole subnet).
Initially when i ran the code approx it took 10 mins to get the result for whole subnet so in order to reduce the time i used multithreaded concept in windows machine but this method is not at all working.
I am pasting the code snippet below.
Even i tried different logic like running 255, 100, 50 ,2 threads at a time but still it failed.
I suspect synchronization issue in this but i don't have any idea to resolve this, so please help me in this getting done.
DWORD WINAPI GetMacAddrOfSubNet(LPVOID lpParam)
{
DWORD dwRetVal;
IPAddr DestIp = 0;
IPAddr SrcIp = 0; /* default for src ip */
ULONG MacAddr[2]; /* for 6-byte hardware addresses */
ULONG PhysAddrLen = 6; /* default to length of six bytes */
char look[100];
strcpy(look ,(char *)lpParam);
DestIp = inet_addr(look);
memset(&MacAddr, 0xff, sizeof (MacAddr));
/*Pinging particular ip and retrning mac addrs if response is thr*/
dwRetVal = SendARP(DestIp, SrcIp, &MacAddr, &PhysAddrLen);
if (dwRetVal == NO_ERROR)
{
/**/
}
return 0;
}
extern "C" __declspec(dllexport) int __cdecl PopulateARPTable(char *IpSubNetMask)
{
char ipn[100];
char buffer[10];
unsigned int k;
DWORD dwThreadIdArray[260];
HANDLE hThreadArray[260];
/*Run 255 threads at once*/
for (k=1; k<255; k++)
{
itoa(k, buffer, 10);
strcpy(ipn, IpSubNetMask);
strcat(ipn, ".");
strcat(ipn, buffer);
/*Thread creation */
hThreadArray[k] = CreateThread( NULL, 0, GetMacAddrOfSubNet, ipn, 0, &dwThreadIdArray[k]);
if (hThreadArray[k] == NULL)
{
//ExitProcess(3);
}
}
WaitForMultipleObjects(255, hThreadArray, TRUE, INFINITE);
return 0;
}
The ipn buffer only exists once. You are using and modifying it as parameter for your (up to) 255 threads. And you expect that the statement strcpy(look ,(char *)lpParam) in the thread will be performed before the main thread modifies ipnagain for calling the next thread. But this is not the case, at least it's not guaranteed. So your threads may use wrong parameters.
Either use different buffers for each thread, or implement a synchronization, that ensures that the parameter has been copied by the thread before main thread modifies the buffer again.
I've done this already for Excel, wrote a multi-threaded DLL that in addition to getting MAC addresses, will do DNS reverse hostname and ICMP ping RT.
Lemme know if you want the VBA code that goes with it. The source for the C-based DLL (which you may be happy with as a template) is:
/*
ExcelNet library: Provide threaded networking functions
NOTE: Serially doing these on the network involves serially waiting for timeouts, much ouchies!
Written by: Danny Holstein
*/
#if 1 // header stuff
#include <windows.h>
#include <iphlpapi.h>
#include <icmpapi.h>
#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <stdbool.h>
#define MSEXPORT __declspec(dllexport)
#define MIN(a,b) (((a)<(b))?(a):(b))
#define MAX(a,b) (((a)>(b))?(a):(b))
#define BUFSZ 256
typedef struct {
char ip[BUFSZ]; // IP addresses in dotted notation.
int ipSize; // size of IP address buffer
char data[BUFSZ]; // general network data (MAC, hostname, etc)
int dataSize; // size of data buffer ^
int err_no; // WinAPI error number
int (*func)(LPCSTR Addr, char* buf, int BufSz); // function address, &GetNameInfos, &GetARP or &GetICMP
} NET_DATA;
int GetARP(LPCSTR Addr, char* Buf, int BufSz);
int GetNameInfos(LPCSTR Addr, char* Buf, int BufSz);
int GetICMP(LPCSTR Addr, char* Buf, int BufSz);
char msg_dbg[BUFSZ], dan[BUFSZ];
#define DEBUG_PRT() {snprintf(msg_dbg, BUFSZ, "lineno = %d\tfunc = %s", __LINE__ , __func__); MessageBox(0, msg_dbg, "debug", 0);}
#define DEBUG_MSG(msg) {snprintf(msg_dbg, BUFSZ, "msg=\"%s\"\tlineno = %d\tfunc = %s", msg, __LINE__ , __func__); MessageBox(0, msg_dbg, "debug", 0);}
#if 0 // documentation indicates malloc/realloc/free shouldn't be used in DLLs
#define malloc(A) malloc(A)
#define realloc(A, B) realloc(A, B)
#define free(A) free(A)
// #define NOMEMLEAK // dudint work
#else // kinda works, when NOT allocating all the NET_DATA structure elements
#define malloc(A) HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY | HEAP_GENERATE_EXCEPTIONS, A)
#define realloc(A, B) HeapReAlloc(GetProcessHeap(), HEAP_GENERATE_EXCEPTIONS, A, B)
#define free(A) (void) HeapFree(A, HEAP_GENERATE_EXCEPTIONS, NULL)
#define NOMEMLEAK
#endif
#endif
MSEXPORT void __stdcall ArrayDGH(SAFEARRAY **IntArr, SAFEARRAY **StrArr)
{
SAFEARRAY *A = (SAFEARRAY*) (*IntArr);
SAFEARRAY *S = (SAFEARRAY*) (*StrArr);
int n = (*A).rgsabound[0].cElements;
snprintf(dan, BUFSZ, "a num elems = %d, str num elems = %d", n, (*S).rgsabound[0].cElements); DEBUG_MSG(dan);
// for (int i=0; i<n; i++) {snprintf(dan, BUFSZ, "elem[%d] = %d", i, ((int*) (*A).pvData)[i]); DEBUG_MSG(dan);}
OLECHAR* str[] = {L"Da",L"Fuk",L"Waz",L"Dat?",L"dot",L"dot"};
for (int i=0; i<n; i++) {SysReAllocString(&(((BSTR*) (*S).pvData)[i]), str[i]);}
}
DWORD dwMilliseconds = 10000;
MSEXPORT void __stdcall SetTIMO(DWORD Timo) {dwMilliseconds = Timo;}
MSEXPORT bool __stdcall ExcelSendARP(LPCSTR Addr, BSTR* MAC)
{
char buf[BUFSZ];
int err = GetARP(Addr, buf, BUFSZ);
*MAC = SysAllocStringByteLen(buf, strlen(buf)); // avoid WIDE to ANSI stuff
return !err;
}
MSEXPORT bool __stdcall ExcelICMPRT(LPCSTR Addr, BSTR* RoundTrip)
{
char buf[BUFSZ];
int err = GetICMP(Addr, buf, BUFSZ);
*RoundTrip = SysAllocStringByteLen(buf, strlen(buf)); // avoid WIDE to ANSI stuff
return !err;
}
MSEXPORT bool __stdcall ExcelGetNameInfo(LPCSTR Addr, BSTR* NameInfo)
{
char buf[BUFSZ];
#ifdef TEST_FUNC_PTR
int (*FunAddr[2])(LPCSTR Addr, char** buf, int BufSz);
FunAddr[0] = &GetARP; FunAddr[1] = &GetNameInfos; // DRY code hooks
int err = (*(FunAddr[1]))(Addr, buf, BUFSZ);
#else
int err = GetNameInfos(Addr, buf, BUFSZ);
#endif
*NameInfo = SysAllocStringByteLen(buf, strlen(buf)); // avoid WIDE to ANSI stuff
return !err;
}
int GetNameInfos(LPCSTR Addr, char* buf, int BufSz)
{
ULONG inet; DWORD resp = 0; HOSTENT *tHI;
struct in_addr addr = { 0 };
if ((inet = inet_addr(Addr)) == INADDR_NONE) {
if (strcpy_s(buf, BufSz, "inet_addr failed and returned INADDR_NONE")) DEBUG_MSG("strcpy_s error!");
return inet;
}
addr.s_addr = inet; tHI = gethostbyaddr((char *) &addr, 4, AF_INET);
if (tHI == NULL) { // no reponse for this IP condition, decode condition and place in PCHAR buf
resp = WSAGetLastError();
FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, 0, resp, 0, buf, BufSz, 0);
return resp;
}
_snprintf_s(buf, BufSz-1, _TRUNCATE, "%s", tHI->h_name); // place hostname in PCHAR buf
return resp; // <- resp = 0, we have a hostname associated with this IP, SUCCESS!
}
int GetARP(LPCSTR Addr, char* buf, int BufSz)
{
#define BUFLEN 6
ULONG pMacAddr[BUFLEN], inet, BufLen = BUFLEN; DWORD resp = 0;
if ((inet = inet_addr(Addr)) == INADDR_NONE) {
if (strcpy_s(buf, BufSz, "inet_addr failed and returned INADDR_NONE")) DEBUG_MSG("strcpy_s error!");
return inet;
}
resp = SendARP(inet, 0, pMacAddr, &BufLen);
if (resp) { // no reponse for this IP condition, decode condition and place in PCHAR buf
FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, 0, resp, 0, buf, BufSz, 0);
return resp;
}
UCHAR *pMacAddrBytes = (UCHAR *) pMacAddr;
_snprintf_s(buf, BufSz, _TRUNCATE, "%02x:%02x:%02x:%02x:%02x:%02x", pMacAddrBytes[0], pMacAddrBytes[1], pMacAddrBytes[2],
pMacAddrBytes[3], pMacAddrBytes[4], pMacAddrBytes[5]); // place MAC in PCHAR buf
return resp; // <- resp = 0, we have a MAC associated with this IP, SUCCESS!
}
int GetICMP(LPCSTR Addr, char* buf, int BufSz)
{
HANDLE hIcmpFile;
ULONG inet; DWORD resp = 0;
char SendData[] = "Data Buffer";
LPVOID ReplyBuffer = NULL;
DWORD ReplySize = 0;
if ((inet = inet_addr(Addr)) == INADDR_NONE) {
if (strcpy_s(buf, BufSz, "inet_addr failed and returned INADDR_NONE")) DEBUG_MSG("strcpy_s error!");
return inet;
}
hIcmpFile = IcmpCreateFile();
if (hIcmpFile == INVALID_HANDLE_VALUE) {
resp = GetLastError();
FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, 0, resp, 0, buf, BufSz, 0);
return resp;
}
// Allocate space for at a single reply
ReplySize = sizeof (ICMP_ECHO_REPLY) + sizeof (SendData) + 8;
ReplyBuffer = (VOID *) malloc(ReplySize);
resp = IcmpSendEcho2(hIcmpFile, NULL, NULL, NULL,
inet, SendData, sizeof (SendData), NULL,
ReplyBuffer, ReplySize, dwMilliseconds);
PICMP_ECHO_REPLY pEchoReply = (PICMP_ECHO_REPLY) ReplyBuffer;
if (resp == 0) { // no reponse for this IP condition, decode condition and place in PCHAR buf
resp = pEchoReply->Status; // WSAGetLastError();
FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, 0, resp, 0, buf, BufSz, 0);
return resp;
}
_snprintf_s(buf, BufSz-1, _TRUNCATE, "%d", ((PICMP_ECHO_REPLY) ReplyBuffer)->RoundTripTime); // place roundtrip time in PCHAR buf (ASCII representation)
IcmpCloseHandle(hIcmpFile);
return 0; // we have a RT time in milliseconds associated with this IP, SUCCESS!
}
NET_DATA *NetData;
DWORD WINAPI tGetDATA(LPVOID NetData)
{
char buf[BUFSZ];
NET_DATA *m = NetData; // stupid me, I had allocated the space, instead of address of, not thinking it all disappears on exit
m->err_no = (*(m->func))(m->ip, buf, BUFSZ); // GetARP, GetNameInfos or GetICMP
if (_snprintf_s(m->data, m->dataSize-1, _TRUNCATE, "%s", buf) == -1) DEBUG_MSG("_snprintf_s error!");
// A resources error may have hit AFTER the calling function has returned, including having the thread/memory deallocated in the calling function
return 0;
}
MSEXPORT BSTR __stdcall ExcelRngNetData(UCHAR *list, ULONG *ErrNos, BSTR *DataArry, DWORD dwMilliseconds, char sep, char FunctType)
{ // take list of IP addresses (newline-separated), create thread for each to get network data. Return results in (sep-separated) BSTR.
int i=0, j, NumIPs=0, k = strlen(list), l=0;
#define NMSZ 100
char nm[NMSZ];
void* FuncAddr[3]; // DRY code hooks
FuncAddr[0] = &GetARP; FuncAddr[1] = &GetNameInfos; FuncAddr[2] = &GetICMP;
while (i<k && sscanf_s(list+i, "%[^\n]\n", nm, NMSZ)){i += strnlen_s(nm, NMSZ) + 1; NumIPs++;} // count newline-separated items before doing malloc(), because realloc() is REALLY resource intensive
NetData = malloc(NumIPs * sizeof(NET_DATA)); i = 0;
while (i<k && sscanf_s(list+i, "%[^\n]\n", nm, NMSZ)){ // load calling routines list into structures
j = strnlen_s(nm, NMSZ) + 1; i += j;
NetData[l].err_no = WAIT_TIMEOUT; // easy way to preset the error to a TIMEOUT, if the thread successfully completes before the timeout, this will be set to reflect its timeout
NetData[l].dataSize = BUFSZ;
NetData[l].func = FuncAddr[FunctType]; // DRY (Don't Repeat Yourself) code hook
if (strncpy_s(NetData[l].ip, (NetData[l].ipSize = BUFSZ), nm, j)) DEBUG_MSG("strcpy_s error!");
l++;
}
HANDLE *tHandles = malloc(NumIPs * sizeof(HANDLE)); DWORD ThreadId;
for (i=0; i<NumIPs; i++){
tHandles[i] = CreateThread(NULL, 0, tGetDATA, &(NetData[i]), 0, &ThreadId);
if (tHandles[i] == NULL) {DEBUG_MSG("Could not create threads!\nExiting now"); ExitProcess(3);}
}
if(WaitForMultipleObjects(NumIPs, tHandles, TRUE, dwMilliseconds) == WAIT_FAILED) {
FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, 0, GetLastError(), 0, dan, BUFSZ, 0); DEBUG_MSG(dan);
// Prolly means too many threads, kicked in when I exceeded 64; ERROR_INVALID_PARAMETER = "The parameter is incorrect"
}
#define CHUNK 1024
#define DATASZ 256 // tested with intentionally small size to check "safe" string functions
wchar_t wcs[DATASZ]; char MacChunk[DATASZ];
char *ans = malloc(CHUNK); int anslen = 0, anssz = CHUNK;
char separator[2]; separator[0] = sep; separator[1] = 0;
for(i=0; i<NumIPs; i++) { // build return BSTR and load array with data
CloseHandle(tHandles[i]); ErrNos[i] = NetData[i].err_no;
if (strncpy_s(MacChunk, DATASZ-1, NetData[i].err_no == 0 ? NetData[i].data : "", NetData[i].dataSize-1)) DEBUG_MSG("strcpy_s error!");
if (i<NumIPs-1 && sep != 0) if (strncat_s(MacChunk, DATASZ-1, separator, 1)) DEBUG_MSG("strcpy_s error!");
while (strnlen_s(MacChunk, DATASZ) > anssz - anslen -1) ans = realloc(ans, (anssz += CHUNK)); // choose CHUNK size to avoid constant realloc(), because realloc() is REALLY resource intensive
if (strncpy_s(&(ans[anslen]), DATASZ-1, MacChunk, DATASZ-1)) DEBUG_MSG("strcpy_s error!"); anslen += strnlen_s(MacChunk, DATASZ); // return data in returned BSTR
MultiByteToWideChar(CP_UTF8, 0,
ErrNos[i] == WAIT_TIMEOUT ? "The wait operation timed out." : NetData[i].data,
-1, wcs, DATASZ-1); // return data in supplied array
SysReAllocString(&DataArry[i], wcs);
}
BSTR r = SysAllocStringByteLen(ans, strlen(ans));
#ifdef NOMEMLEAK
free(NetData); free(tHandles); free(ans);
#endif
return r;
}
Can someone provide me with a sample C code that list´s all device Names that i can open with Createfile()? i always get error code 3 : path does not exist
sample code that doesnt works:
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <windows.h>
#include <regstr.h>
#include <devioctl.h>
#include <usb.h>
#include <usbiodef.h>
#include <usbioctl.h>
#include <usbprint.h>
#include <setupapi.h>
#include <devguid.h>
#include <wdmguid.h>
#pragma comment(lib, "Setupapi.lib")
int main(void){
HDEVINFO deviceInfoList;
deviceInfoList = SetupDiGetClassDevs(NULL, NULL, NULL, DIGCF_ALLCLASSES | DIGCF_PRESENT);
if (deviceInfoList != INVALID_HANDLE_VALUE)
{
SP_DEVINFO_DATA deviceInfoData;
deviceInfoData.cbSize = sizeof(SP_DEVINFO_DATA);
for (DWORD i = 0; SetupDiEnumDeviceInfo(deviceInfoList, i, &deviceInfoData); i++)
{
LPTSTR buffer = NULL;
DWORD buffersize = 0;
while (!SetupDiGetDeviceInstanceIdA(deviceInfoList, &deviceInfoData, buffer, buffersize, &buffersize))
{
if (GetLastError() == ERROR_INSUFFICIENT_BUFFER)
{
if (buffer) delete buffer;
buffer = new TCHAR[buffersize];
}
else
{
printf("%ls\n", "error");
break;
}
}
HANDLE hFile = CreateFileA(buffer,
GENERIC_READ,
0,
NULL,
OPEN_EXISTING,
0,
NULL);
if (hFile == INVALID_HANDLE_VALUE) {
printf("InvalidHandle, error code: %d\n", GetLastError());
}
CloseHandle(hFile);
printf("%s\n", buffer);
if (buffer) { delete buffer; buffer = NULL; }
}
}
getchar();
}
my Goal is to print all valid device Names and try to get a valid handle on it that i can later user for sending ioctl`s
thx
EDIT:
ok abhineet so thats what i got now :
DWORD EnumerateDevices(){
DWORD dwResult = 0;
HDEVINFO hdev = SetupDiGetClassDevs(&GUID_DEVCLASS_BATTERY, 0, 0, DIGCF_PRESENT | DIGCF_DEVICEINTERFACE);// DIGCF_ALLCLASSES
/*HDEVINFO hdev =SetupDiGetClassDevs(NULL,
0, // Enumerator
0,
DIGCF_PRESENT | DIGCF_ALLCLASSES); */
if (INVALID_HANDLE_VALUE != hdev) {
for (int idev = 0; idev < 100; idev++)
{
SP_DEVICE_INTERFACE_DATA did = { 0 };
did.cbSize = sizeof(did);
if (SetupDiEnumDeviceInterfaces(hdev, NULL, &GUID_DEVCLASS_BATTERY, idev, &did))
{
DWORD cbRequired = 0;
SetupDiGetDeviceInterfaceDetail(hdev,
&did,
NULL,
0,
&cbRequired,
0);
if (ERROR_INSUFFICIENT_BUFFER == GetLastError())
{
PSP_DEVICE_INTERFACE_DETAIL_DATA pdidd = (PSP_DEVICE_INTERFACE_DETAIL_DATA)LocalAlloc(LPTR, cbRequired);
if (pdidd) {
pdidd->cbSize = sizeof(*pdidd);
if (SetupDiGetDeviceInterfaceDetail(hdev, &did, pdidd, cbRequired, &cbRequired, 0)) {
wprintf(L"%s\n", pdidd->DevicePath);
HANDLE hBattery = CreateFile(pdidd->DevicePath,
GENERIC_READ | GENERIC_WRITE,
FILE_SHARE_READ | FILE_SHARE_WRITE,
NULL,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL,
NULL);
if (INVALID_HANDLE_VALUE != hBattery)
{
printf("Successfully opened Handle\n");
CloseHandle(hBattery);
}
else{
wprintf(L"CreateFile(%s) failed %d\n", pdidd->DevicePath, GetLastError());
}
}
else{
printf("SetupDiGetDeviceInterfaceDetail() failed %d\n", GetLastError());
}
LocalFree(pdidd);
}
}
else{
printf("SetupDiGetDeviceInterfaceDetail() failed %d\n", GetLastError());
}
}
else if (ERROR_NO_MORE_ITEMS == GetLastError())
{
printf("-NoMoreItems-");
break; // Enumeration failed - perhaps we're out of items
}
}
SetupDiDestroyDeviceInfoList(hdev);
}
else{
printf("SetupDiGetClassDevs() failed %d\n", GetLastError());
}
return dwResult;
}
i ripped the most from here : https://msdn.microsoft.com/en-us/library/windows/desktop/bb204769(v=vs.85).aspx
and my Output is :
\\?\acpi#pnp0c0a#1#{72631e54-78a4-11d0-bcf7-00aa00b7b32a}
Successfully opened Handle
-NoMoreItems-
at least i got a valid handle!
so i wanna do this an all devices avaible on the System , how to do that?
IMHO, I don't think, you can do a CreateFile on InstanceID. To do a CreateFile, you need the symbolic name of the device. You can use the following SetupAPIs,
SetupDiEnumDeviceInterfaces
SetupDiGetDeviceInterfaceDetail
The Remark section of both APIs state that,
SetupDiEnumDeviceInterfaces:: DeviceInterfaceData points to a structure that identifies a requested
device interface. To get detailed information about an interface, call
SetupDiGetDeviceInterfaceDetail. The detailed information includes the
name of the device interface that can be passed to a Win32 function
such as CreateFile (described in Microsoft Windows SDK documentation)
to get a handle to the interface.
SetupDiGetDeviceInterfaceDetail:: The interface detail returned by this function consists of a device path that can be passed to Win32
functions such as CreateFile. Do not attempt to parse the device path
symbolic name. The device path can be reused across system starts.
This might be of your use, how to get DevicePath from DeviceID
I am trying to send arguments to my arduino. so i made this code:
#include <windows.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
HANDLE serialPortHandler;
char *comPort[8] = {"1", "2", "3", "4", "5", "6", "7", "8"};
char comPortName[5] = "COM";
int i = 1;
int openPort(char *name){
serialPortHandler = CreateFile(name, GENERIC_READ | GENERIC_WRITE, 0, 0, OPEN_EXISTING, 0, 0);
if(serialPortHandler == INVALID_HANDLE_VALUE){
return -1;
}else{
DCB dcb;
FillMemory(&dcb, sizeof(dcb), 0);
if (!GetCommState(serialPortHandler, &dcb)){
return -1;
}
dcb.BaudRate = CBR_9600 ;
if (!SetCommState(serialPortHandler, &dcb)){
return -1;
}
}
return 1;
}
int writePort(char *lpBuf,DWORD dwToWrite){
DWORD dwWritten;
if(WriteFile(serialPortHandler, lpBuf, dwToWrite, &dwWritten, NULL)){
while(dwWritten < dwToWrite);
printf("User: %s, %d", lpBuf, dwWritten);
return 0;
}else{
printf("Error");
CloseHandle(serialPortHandler);
return 1;
}
return 0;
}
int main(int argc, char *argv[]){
if(argc != 2)
return 1;
strcat(comPortName, comPort[0]);
while(openPort(comPortName) < 0 && i < sizeof(comPort) / sizeof(int)){
comPortName[3] = *comPort[i];
//printf("%s", comPortName);
i++;
Sleep(0);
}if(i >= sizeof(comPort) / sizeof(int)){
printf("Cannot Find Port");
scanf("%d");
return 1;
}
printf("Port %s Is Opened - BaudRate 9600\n", comPortName);
printf("Sent Frequency: %s\n", argv[1]);
writePort(argv[1], strlen(argv[1]));
}
But it only works if i run it on debug mode and wait for a few moments at WriteFile.If i run it from cmd it doesnt output to my arduino.
The WriteFile function has the ability to run asynchronously. Have you checked for this case?
From:https://msdn.microsoft.com/en-us/library/windows/desktop/aa365747(v=vs.85).aspx
If the function fails, or is completing asynchronously, the return value is zero (FALSE). To get extended error information, call the GetLastError function.
The WriteFile function returns when one of the following conditions occur:
The number of bytes requested is written.
A read operation releases buffer space on the read end of the pipe (if the write was blocked). For more information, see the Pipes section.
An asynchronous handle is being used and the write is occurring asynchronously.
An error occurs.
(Meta: Can't blockquote a bullet list, I guess)
The problem was it takes time to initiate these two things:
1.SetCommState(serialPortHandler, &dcb)
so i added Sleep before and it fixed the problem.
I'm (synchronously) reading serial input in Windows using ReadFile(), but instead of waiting for the serial port to have input then returning that as I thought it should, ReadFile() instead returns immediately with a value of FALSE, and a GetLastError() of 0. (Yes, I'm certain I have the right error code and am not making syscalls in between).
The ReadFile() documentation says that when the function "is completing asynchronously, the return value is zero (FALSE)." How is it that a synchronous read can be completing asychronously? Why would this be an error? It's worth noting that the data read is garbage data, as one might expect.
More generally, how can I force ReadFile() to behave like a simple synchronous read of a serial port, or at least behave something like the UNIX read()?
Edit: Here is some source code:
HANDLE my_connect(char *port_name)
{
DCB dcb;
COMMTIMEOUTS timeouts;
HANDLE hdl = CreateFile(port_name,
GENERIC_READ | GENERIC_WRITE,
0,
NULL,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL,
0);
GetCommState(port_name, &dcb);
dcb.BaudRate = 115200;
dcb.ByteSize = 8;
dcb.StopBits = ONESTOPBIT;
dcb.Parity = NOPARITY;
if(SetCommState(hdl, &dcb) == 0)
{
fprintf(stderr, "SetCommState failed with error code %d.\n",
GetLastError());
return (HANDLE) -1;
}
/* TODO: Set a variable timeout. */
timeouts.ReadIntervalTimeout = 0;
timeouts.ReadTotalTimeoutMultiplier = 0;
timeouts.ReadTotalTimeoutConstant = 5000; /* wait 5s for input */
timeouts.WriteTotalTimeoutMultiplier = 0;
timeouts.WriteTotalTimeoutConstant = 5000;
if(SetCommTimeouts(hdl, &timeouts) == 0)
{
fprintf(stderr, "SetCommTimeouts failed with error code %d.\n",
GetLastError());
return (HANDLE) -1;
}
return hdl;
}
int my_disconnect(HANDLE hdl)
{
return CloseHandle(hdl);
}
int my_send(HANDLE hdl, char *cmd)
{
DWORD nb = 0;
if(WriteFile(hdl, cmd, strlen(cmd), &nb, NULL) == 0)
{
fprintf(stderr, "WriteFile failed with error code %d.\n",
GetLastError());
return -1;
}
return (int) nb;
}
int my_receive(HANDLE hdl, char *dst, int dstlen)
{
int i;
DWORD r;
BOOL err;
char c = '\0';
for (i = 0; i < dstlen; err = ReadFile(hdl, &c, 1, &r, NULL))
{
if (err == 0)
{
fprintf(stderr, "ReadFile failed with error code %d.\n",
GetLastError());
return -1;
}
if (r > 0)
{
dst[i++] = c;
if (c == '\n') break;
}
}
if (i == dstlen)
{
fprintf(stderr, "Error: read destination buffer not large enough.\
Recommended size: 256B. Your size: %dB.\n", dstlen);
return -1;
}
else
{
dst[i] = '\0'; /* null-terminate the string. */
}
return i;
}
And my test code:
HANDLE hdl = my_connect("COM4");
char *cmd = "/home\n"; /* basic command */
char reply[256];
my_send(hdl, cmd);
my_receive(hdl, reply, 256);
puts(reply);
It's not completing asynchronously. If it were, GetLastError would return ERROR_IO_PENDING.
To do synchronous I/O, open the file without FILE_FLAG_OVERLAPPED.
It should not be possible for ReadFile to fail without a valid GetLastError code. ReadFile only returns false when the driver sets a non-success status code.
I am trying to make a named Windows pipe in C. The pipe is used by a user and a server. The user sends trough the pipe a random int. Then the server searches in its current directory a file with the size greater or equal with the received int, and then sends back to the user the file name and a maximum of 100 bytes from the file.
My problem is that i don't know how to verify the size of every file from the directory, and then to return the filename and 100 bytes.
This is the function i'm trying to use for measuring a file size:
int fsize(char* file)
{
FILE * f = fopen(file, "r");
fseek(f, 0, SEEK_END);
int len = (unsigned long)ftell(f);
fclose(f);
return len;
}
This is the "client" code:
#include <stdio.h>
#include <windows.h>
#define MAXLINIE 100
int main(int argc, char* argv[]) {
char rcvMsg[100];
char sndMsg[100];
DWORD rez;
HANDLE readHandle, writeHandle;
int r = rand();
char str[15];
sprintf(str, "%d", r);
writeHandle = CreateFile("\\\\.\\PIPE\\FirstPipe", GENERIC_WRITE, FILE_SHARE_WRITE,
NULL, OPEN_EXISTING, 0, NULL);
readHandle = CreateFile("\\\\.\\PIPE\\SecondPipe",GENERIC_READ, FILE_SHARE_READ,
NULL, OPEN_EXISTING, 0, NULL);
strcpy(sndMsg, r);
printf("Sending message to server: %s\n", sndMsg);
WriteFile(writeHandle, sndMsg, strlen(sndMsg), &rez, NULL);
printf("Message sent! Waiting for server to read the message!\n");
printf("Waiting for SERVER to write in the pipe...\n");
ReadFile(readHandle, rcvMsg, 100, &rez, NULL);
printf("Client revceived message: %s\n", rcvMsg);
CloseHandle(readHandle);
CloseHandle(writeHandle);
return 1;
}
This is the "server" code, excepting the file parsing part:
>
#include <stdio.h>
#include <windows.h>
#define MAXLINIE 100
//file lenght
int fsize(char* file)
{
FILE * f = fopen(file, "r");
fseek(f, 0, SEEK_END);
int len = (unsigned long)ftell(f);
fclose(f);
return len;
}
int main(int argc, char* argv[]) {
char rcvMsg[100];
char sndMsg[100];
DWORD rez;
HANDLE readHandle, writeHandle;
readHandle = CreateNamedPipe("\\\\.\\PIPE\\FirstPipe", PIPE_ACCESS_INBOUND,
PIPE_TYPE_BYTE|PIPE_WAIT,3,0,0,0,NULL);
writeHandle = CreateNamedPipe("\\\\.\\PIPE\\SecondPipe", PIPE_ACCESS_OUTBOUND,
PIPE_TYPE_BYTE|PIPE_WAIT, 3, 0, 0, 0, NULL);
printf("Waiting for clients to connect...\n");
ConnectNamedPipe(writeHandle, NULL);
ConnectNamedPipe(readHandle, NULL);
printf("Waiting for a CLIENT to write in the pipe...\n");
ReadFile(readHandle, rcvMsg, 100, &rez, NULL);
printf("Server revceived message: %s\n", rcvMsg);
int num = atoi(rcvMsg); //the file lenght i'm looking for
//here i should process the files
strcpy(sndMsg, "File_name + 100 bytes");
printf("Server sends an answer: %s\n", sndMsg);
WriteFile(writeHandle, sndMsg, strlen(sndMsg), &rez, NULL);
printf("Waiting for client to read the message...\n");
// disconnecting and closing the handles
DisconnectNamedPipe(writeHandle);
CloseHandle(writeHandle);
DisconnectNamedPipe(readHandle);
CloseHandle(readHandle);
return 1;
}
FindFirstFile() and FindNextFile() to iterate through files... supports wildcards. When done call FindClose()
http://msdn.microsoft.com/en-us/library/windows/desktop/aa364418(v=vs.85).aspx
Here is example code using FindFirstFile from cprogramming: (look in wfd struct for size attributes)
see other comments below code example
#include <stdio.h>
#include <string.h>
#include <windows.h>
void find(char* path,char* file) //Note: pass the path string appropriate for your scenario
{
static int found =0;
HANDLE fh;
WIN32_FIND_DATA wfd;
int i=0;
int j=0;
fh=FindFirstFile(path,&wfd);
if(fh)
{
if(strcmp(wfd.cFileName,file)==0)
{
path[strlen(path)-3]='\0';
strcat(path,file);
FindClose(fh);
return;
}
else
{
while(FindNextFile(fh,&wfd) && found ==0)
{
if(strcmp(wfd.cFileName,file)==0)
{
path[strlen(path)-3]='\0';
strcat(path,file);
FindClose(fh);
found =1;
return;
}
if(wfd.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY &&
strcmp(wfd.cFileName,"..")!=0 && strcmp(wfd.cFileName,".")!=0)
{
path[strlen(path)-3]='\0';
strcat(path,wfd.cFileName);
strcat(path,"\\*.*");
find(path,file);
}
}
if(found==0)
{
for(i=strlen(path)-1;i>0;i--)
{
if(j==1 && path[i]=='\\')
{
path[i]='\0';
strcat(path,"\\*.*");
break;
}
if(path[i]=='\\')
j=1;
}
}
}
FindClose(fh);
}
}
int main()
{
TCHAR path[512] = "C:\\*.*"; //Change this as necessary
find(path,"notepad.exe");
printf("%s\n",path);
return 0;
}
The file attributes will give you the file name, and size etc.
You can then write the 100 bytes to a char buffer by passing the name and path of the found file to fopen(): FILE *fp = fopen(fileNamePath, "r"); Then something like char buf[101];for(i=0;i<100;i++){buf[i] = fgetc(fp);}
***Don't forget to use fclose() when you are done with fp.