I am using libssh.
After calling ssh_channel_write, I have to know whether there has data to read. (But I don't want to retrieve data.)
If there has no data to read (for example, after 10s), I will call ssh_channel_write again.
Both of ssh_channel_read and ssh_channel_read_nonblocking cannot do this. (And checking ssh_get_status with SSH_READ_PENDING also does not work.)
Is there any ways to solve this problem?
It's NonBlocking ...
Use the ssh_select() function. It works quite similar to the regular select(), but uses channels instead of sockets.
int ssh_select (ssh_channel *channels, ssh_channel *outchannels,
socket_t maxfd, fd_set *readfds, struct timeval *timeout);
For instance, a single channel implementation:
ssh_channel channels[2];
ssh_channel myChannel = ssh_channel_new (ssh_session session);
channels[0] = myChannel;
channels[1] = NULL;
struct timeval timeout = (0, 200000); // 0 seconds, 200 millis
int rc = ssh_select (channels, NULL, NULL, NULL, &timeout);
if (rc > 0) {// There is a pending data.
if (rc < 0) // the ssh_select() error.
if (rc == 0) // You've got a broken connection.
Related
I made a connection to BitCoin node via WinSock2. I sent the proper "getaddr" message and then the server responds, the replied data are ready to read, because Select() notifies this, but when I call Recv() there are 0 bytes read.
My code is working OK on localhost test server. The incomplete "getaddr" message (less than 24 bytes) is NOT replied by BitCoin node, only proper message, but I can't read the reply with Recv(). After returning 0 bytes, the Select() still returns there are data to read.
My code is divided into DLL which uses Winsock2 and the main() function.
Here are key fragments:
struct CMessageHeader
{
uint32_t magic;
char command[12];
uint32_t payload;
uint32_t checksum;
};
CSocket *sock = new CSocket();
int actual; /* Actually read/written bytes */
sock->connect("109.173.41.43", 8333);
CMessageHeader msg = { 0xf9beb4d9, "getaddr\0\0\0\0", 0, 0x5df6e0e2 }, rcv = { 0 };
actual = sock->send((const char *)&msg, sizeof(msg));
actual = sock->select(2, 0); /* Select read with 2 seconds waiting time */
actual = sock->receive((char *)&rcv, sizeof(rcv));
The key fragment of DLL code:
int CSocket::receive(char *buf, int len)
{
int actual;
if ((actual = ::recv(sock, buf, len, 0)) == SOCKET_ERROR) {
std::ostringstream s;
s << "Nie mozna odebrac " << len << " bajtow.";
throw(CError(s));
}
return(actual);
}
If select() reports the socket is readable, and then recv() returns 0 afterwards, that means the peer gracefully closed the connection on their end (ie, sent a FIN packet to you), so you need to close your socket.
On a side note, recv() can return fewer bytes than requested, so your receive() function should call recv() in a loop until all of the expected bytes have actually been received, or an error occurs (same with send(), too).
I am experiencing a strange problem when trying to use the GMFBridge filter with the output of an Euresys UxH264 card.
I am trying to integrate this card into our solution, that relies on GMFBridge to handle the ability of continuous capture to multiple files, performing muxing and file-splitting without having to stop the capture graph.
This card captures video and audio from analog inputs. It provides a DirectShow filter exposing both a raw stream of the video input and a hardware-encoded H.264 stream. The audio stream is provided as an uncompressed stream only.
When I attempt to directly connect any of the output pins of the Euresys source filters to the input pins of the GMFBridge Sink, they get rejected, with the code VFW_E_NO_ALLOCATOR. (In the past I have successfully connected both H.264 and raw audio streams to the bridge).
Grasping at straws, I plugged in a pair of SampleGrabber filters between the Euresys card filters and the bridge sink filter, and -just like that- the connections between sample grabbers and sink were accepted.
However, I am not getting any packets on the other side of the bridge (the muxing graph). I inspected the running capture graph with GraphStudioNext and somehow the sample grabbers appear detached from my graph, even though I got successful confirmations when I connected them to the source filter!.
Here's the source code creating the graph.
void EuresysSourceBox::BuildGraph() {
HRESULT hRes;
CComPtr<IGraphBuilder> pGraph;
COM_CALL(pGraph.CoCreateInstance(CLSID_FilterGraph));
#ifdef REGISTER_IN_ROT
_rotEntry1 = FilterTools::RegisterGraphInROT(IntPtr(pGraph), "euresys graph");
#endif
// [*Video Source*]
String^ filterName = "Ux H.264 Visual Source";
Guid category = _GUIDToGuid((GUID)AM_KSCATEGORY_CAPTURE);
FilterMonikerList^ videoSourceList = FilterTools::GetFilterMonikersByName(category, filterName);
CComPtr<IBaseFilter> pVideoSource;
int monikerIndex = config->BoardIndex; // a filter instance will be retrieved for every installed board
clr_scoped_ptr<CComPtr<IMoniker>>^ ppVideoSourceMoniker = videoSourceList[monikerIndex];
COM_CALL((*ppVideoSourceMoniker->get())->BindToObject(NULL, NULL, IID_IBaseFilter, (void**)&pVideoSource));
COM_CALL(pGraph->AddFilter(pVideoSource, L"VideoSource"));
// [Video Source]
//
// [*Audio Source*]
filterName = "Ux H.264 Audio Encoder";
FilterMonikerList^ audioSourceList = FilterTools::GetFilterMonikersByName(category, filterName);
CComPtr<IBaseFilter> pAudioSource;
clr_scoped_ptr<CComPtr<IMoniker>>^ ppAudioSourceMoniker = audioSourceList[monikerIndex];
COM_CALL((*ppAudioSourceMoniker->get())->BindToObject(NULL, NULL, IID_IBaseFilter, (void**)&pAudioSource));
COM_CALL(pGraph->AddFilter(pAudioSource, L"AudioSource"));
CComPtr<IPin> pVideoCompressedOutPin(FilterTools::GetPin(pVideoSource, "Encoded"));
CComPtr<IPin> pAudioOutPin(FilterTools::GetPin(pAudioSource, "Audio"));
CComPtr<IBaseFilter> pSampleGrabber;
COM_CALL(pSampleGrabber.CoCreateInstance(CLSID_SampleGrabber));
COM_CALL(pGraph->AddFilter(pSampleGrabber, L"SampleGrabber"));
CComPtr<IPin> pSampleGrabberInPin(FilterTools::GetPin(pSampleGrabber, "Input"));
COM_CALL(pGraph->ConnectDirect(pVideoCompressedOutPin, pSampleGrabberInPin, NULL)); // DOES NOT FAIL!!
CComPtr<IBaseFilter> pSampleGrabber2;
COM_CALL(pSampleGrabber2.CoCreateInstance(CLSID_SampleGrabber));
COM_CALL(pGraph->AddFilter(pSampleGrabber2, L"SampleGrabber2"));
CComPtr<IPin> pSampleGrabber2InPin(FilterTools::GetPin(pSampleGrabber2, "Input"));
COM_CALL(pGraph->ConnectDirect(pAudioOutPin, pSampleGrabber2InPin, NULL)); // DOES NOT FAIL!!
// [Video Source]---
// |-->[*Bridge Sink*]
// [Audio Source]---
CComPtr<IPin> pSampleGrabberOutPin(FilterTools::GetPin(pSampleGrabber, "Output"));
CComPtr<IPin> pSampleGrabber2OutPin(FilterTools::GetPin(pSampleGrabber2, "Output"));
CreateGraphBridge(
IntPtr(pGraph),
IntPtr(pSampleGrabberOutPin),
IntPtr(pSampleGrabber2OutPin)
);
// Root graph to parent object
_ppCaptureGraph.reset(new CComPtr<IGraphBuilder>(pGraph));
}
COM_CALL is my HRESULT checking macro, it will raise a managed exception if the result is other than S_OK. So the connection between pins succeeded, but here is how the graph looks disjointed when it is running:
So, I have three questions:
1) What could VFW_E_NO_ALLOCATOR mean in this instance? (the source filter can be successfully connected to other components such as LAV Video decoder or ffdshow video decoder).
2) Is there a known workaround to circumvent the VFW_E_NO_ALLOCATOR problem?
3) Is it possible that a filter gets disconnected at runtime as it seems to be happening in my case?
I found a reference by Geraint Davies giving a reason as to why the GMFBridge sink filter may be rejecting the connection.
It looks as though the parser is insisting on using its own allocator
-- this is common with parsers where the output samples are merely pointers into the input samples. However, the bridge cannot implement
suspend mode without using its own allocator, so a copy is required.
With this information, I decided to create an ultra simple CTransformFilter filter that simply accepts the allocator offered by the bridge and copies to the output sample whatever comes in from the input sample. I am not 100% sure that what I did was right, but it is working now. I could successfully plug-in the Euresys card as part of my capture infrastructure.
For reference, if anyone experiences something similar, here is the code of the filter I created:
class SampleCopyGeneratorFilter : public CTransformFilter {
protected:
HRESULT CheckInputType(const CMediaType* mtIn) override { return S_OK; }
HRESULT GetMediaType(int iPosition, CMediaType* pMediaType) override;
HRESULT CheckTransform(const CMediaType *mtIn, const CMediaType *mtOut) override { return S_OK; }
HRESULT DecideBufferSize(IMemAllocator *pAlloc, ALLOCATOR_PROPERTIES *pProp) override;
HRESULT Transform(IMediaSample *pSource, IMediaSample *pDest) override;
public:
SampleCopyGeneratorFilter();
};
//--------------------------------------------------------------------------------------------------------------------
SampleCopyGeneratorFilter::SampleCopyGeneratorFilter()
: CTransformFilter(NAME("SampleCopyGeneratorFilter"), NULL, GUID_NULL)
{
}
HRESULT SampleCopyGeneratorFilter::GetMediaType(int iPosition, CMediaType* pMediaType) {
HRESULT hRes;
ASSERT(m_pInput->IsConnected());
if( iPosition < 0 )
return E_INVALIDARG;
CComPtr<IPin> connectedTo;
COM_CALL(m_pInput->ConnectedTo(&connectedTo));
CComPtr<IEnumMediaTypes> pMTEnumerator;
COM_CALL(connectedTo->EnumMediaTypes(&pMTEnumerator));
AM_MEDIA_TYPE* pIteratedMediaType;
for( int i = 0; i <= iPosition; i++ ) {
if( pMTEnumerator->Next(1, &pIteratedMediaType, NULL) != S_OK )
return VFW_S_NO_MORE_ITEMS;
if( i == iPosition )
*pMediaType = *pIteratedMediaType;
DeleteMediaType(pIteratedMediaType);
}
return S_OK;
}
HRESULT SampleCopyGeneratorFilter::DecideBufferSize(IMemAllocator *pAlloc, ALLOCATOR_PROPERTIES *pProp) {
HRESULT hRes;
AM_MEDIA_TYPE mt;
COM_CALL(m_pInput->ConnectionMediaType(&mt));
try {
BITMAPINFOHEADER* pBMI = HEADER(mt.pbFormat);
pProp->cbBuffer = DIBSIZE(*pBMI); // format is compressed, uncompressed size should be enough
if( !pProp->cbAlign )
pProp->cbAlign = 1;
pProp->cbPrefix = 0;
pProp->cBuffers = 4;
ALLOCATOR_PROPERTIES actualProperties;
COM_CALL(pAlloc->SetProperties(pProp, &actualProperties));
if( pProp->cbBuffer > actualProperties.cbBuffer )
return E_FAIL;
return S_OK;
} finally{
FreeMediaType(mt);
}
}
HRESULT SampleCopyGeneratorFilter::Transform(IMediaSample *pSource, IMediaSample *pDest) {
HRESULT hRes;
BYTE* pBufferIn;
BYTE* pBufferOut;
long destSize = pDest->GetSize();
long dataLen = pSource->GetActualDataLength();
if( dataLen > destSize )
return VFW_E_BUFFER_OVERFLOW;
COM_CALL(pSource->GetPointer(&pBufferIn));
COM_CALL(pDest->GetPointer(&pBufferOut));
memcpy(pBufferOut, pBufferIn, dataLen);
pDest->SetActualDataLength(dataLen);
pDest->SetSyncPoint(pSource->IsSyncPoint() == S_OK);
return S_OK;
}
Here is how I inserted the filter in the capture graph:
CComPtr<IPin> pAACEncoderOutPin(FilterTools::GetPin(pAACEncoder, "XForm Out"));
CComPtr<IPin> pVideoSourceCompressedOutPin(FilterTools::GetPin(pVideoSource, "Encoded"));
CComPtr<IBaseFilter> pSampleCopier;
pSampleCopier = new SampleCopyGeneratorFilter();
COM_CALL(pGraph->AddFilter(pSampleCopier, L"SampleCopier"));
CComPtr<IPin> pSampleCopierInPin(FilterTools::GetPin(pSampleCopier, "XForm In"));
COM_CALL(pGraph->ConnectDirect(pVideoSourceCompressedOutPin, pSampleCopierInPin, NULL));
CComPtr<IPin> pSampleCopierOutPin(FilterTools::GetPin(pSampleCopier, "XForm Out"));
CreateGraphBridge(
IntPtr(pGraph),
IntPtr(pSampleCopierOutPin),
IntPtr(pAACEncoderOutPin)
);
Now, I still have no idea why inserting the sample grabber instead did not work and resulted in detached graphs. I corroborated this quirk by examining the graphs with Graphedit Plus too. If anyone can offer me an explanation, I would be very grateful indeed.
I'm starter of RTOS and I'm using Xenomai v2.6.3.
I'm trying to get some data using Serial communication.
I did my best on the task following the xenomai's guide and open sources, but it doesn't work well.
the link of the guide --> (https://xenomai.org//serial-16550a-driver/)
I just followed the sequence to use the module xeno_16550A. (with port io = 0x2f8 and irq=3)
I followed open source http://www.acadis.org/pages/captain.at/serial-port-example
It works well in write task, but read task doesn't work well.
It gave me the error sentence with error while RTSER_RTIOC_WAIT_EVENT, code -110 (it means connection timed out)
Moreover I checked the irq number3 by typing command 'cat /proc/xenomai/irq', but the interrupt number doesn't increase.
In my case, I don't need to write data, so I erase the write task code.
The read task proc is follow
void read_task_proc(void *arg) {
int ret;
ssize_t red = 0;
struct rtser_event rx_event;
while (1) {
/* waiting for event */
ret = rt_dev_ioctl(my_fd, RTSER_RTIOC_WAIT_EVENT, &rx_event );
if (ret) {
printf(RTASK_PREFIX "error while RTSER_RTIOC_WAIT_EVENT, code %d\n",ret);
if (ret == -ETIMEDOUT)
continue;
break;
}
unsigned char buf[1];
red = rt_dev_read(my_fd, &buf, 1);
if (red < 0 ) {
printf(RTASK_PREFIX "error while rt_dev_read, code %d\n",red);
} else {
printf(RTASK_PREFIX "only %d byte received , char : %c\n",red,buf[0]);
}
}
exit_read_task:
if (my_state & STATE_FILE_OPENED) {
if (!close_file( my_fd, READ_FILE " (rtser)")) {
my_state &= ~STATE_FILE_OPENED;
}
}
printf(RTASK_PREFIX "exit\n");
}
I could guess the causes of the problem.
buffer size or buffer is already full when new data is received.
rx_interrupt doesn't work....
I want to check whether the two things are wrong or not, but How can I check?
Furthermore, does anybody know the cause of the problem? Please give me comments.
I have used the following code to get the cpu frequency .
-(int) returnCPUFreq
{
size_t length;
int mib[6];
int result;
mib[0] = CTL_HW;
mib[1] = HW_CPU_FREQ;
length = sizeof(result);
sysctl(mib, 2, &result, &length, NULL, 0);
return result;
}
It is giving the 6 digits code and it is varying for every time when I run the app . i.e the output is first time 644311 , second time 303921 .....
Is this code correct ? Is the values vary for everytime when I run the app?
Your answer is correct. You could check wether sysctl return no error by checking sysctl(mib, 2, &result, &length, NULL, 0) < 0
But this won't change anything in the varying frequency. This is because Apple doesn't allow reading the frequency for all of their products.
When you need it to determine how many details or something like that you can enable I would check on the hardware model and look up the cpu frequency in an nsdictionary where i placed all the available hardware models.
I'm working on a jailbreak app, and want to send SIGKILL messages to specific apps that may be running on a user's device (with their permission, of course).
Google is not turning up anything for me. Is there a plist or array that keeps track of running processes?
Thanks for any help you all can give, you're wonderful!
Make a sysctl API and retrieve the kinfo_proc structure http://fxr.watson.org/fxr/source/sys/kinfo.h?v=DFBSD. This struct has information about running processes.You can run it in a loop until to get info about all processes. Here is a code snippet- extend it to get info of all processes
mib[0] = CTL_KERN;
mib[1] = KERN_PROC;
mib[2] = KERN_PROC_ALL;
mib[3] = 0;
ret = sysctl(mib, 4, NULL, &size, NULL, 0);
procs = malloc(size);
ret = sysctl(mib, 4, procs, &size, NULL, 0); /* procs is struct kinfo_proc.*/