Develop Reference

Is it possible to connect to a 32 bit C++ RPC Server application from a C# application

Let me attempt to briefly explain what I am trying to accomplish here...
I have used the Remote Procedure call (RPC) approach to develop a Client application in C++ and a Server application also in C++. The Client is 64 bit and the Server is 32 bit. The goal of this effort was to use the Client to pass variables to functions on the Server side. Then the Server would use a 32 bit .dll to process the data that was received and return the outputted values back to the Client. This process is working very well and I couldn't be happier with it.
I am working with a 64 bit application that was developed in C# and has a static class for sending variables to a .dll and returning the values outputted. Because this application is 64 bit it cannot be connected to the 32 bit .dll (duh) that is required for these computations.
Now for my question...
Is there any way I can keep the process I have already developed in C++ and access the 32 bit Server from the 64 bit C# project? Is there a better approach for this all together?
EDIT:
I should also include I am using the rpcrt4.lib and here is my Client sample code.
int main()
{
RPC_STATUS status;
unsigned char* szStringBinding = NULL;
char temppath[MAX_PATH] = {0};
// Creates a string binding handle.
// This function is nothing more than a printf.
// Connection is not done here.
status = RpcStringBindingCompose(
NULL, // UUID to bind to.
reinterpret_cast<unsigned char*>("ncacn_ip_tcp"), // Use TCP/IP
// protocol.
reinterpret_cast<unsigned char*>("localhost"), // TCP/IP network
// address to use.
reinterpret_cast<unsigned char*>("4747"), // TCP/IP port to use.
NULL, // Protocol dependent network options to use.
&szStringBinding); // String binding output.
if (status)
exit(status);
// Validates the format of the string binding handle and converts
// it to a binding handle.
// Connection is not done here either.
status = RpcBindingFromStringBinding(
szStringBinding, // The string binding to validate.
&hRPCProjectBinding); // Put the result in the implicit binding
// handle defined in the IDL file.
if (status)
exit(status);
RpcTryExcept
{
// Calls the RPC function. The hRPCProjectBinding binding handle
// is used implicitly.
// Connection is done here.
Output((unsigned char*)"Implcicit RPC Server Call from Client ");
system("PAUSE");
ShutDown();
}
RpcExcept(1)
{
std::cerr << "Runtime reported exception " << RpcExceptionCode()
<< std::endl;
}
RpcEndExcept
// Free the memory allocated by a string.
status = RpcStringFree(
&szStringBinding); // String to be freed.
if (status)
exit(status);
// Releases binding handle resources and disconnects from the server.
status = RpcBindingFree(
&hRPCProjectBinding); // Frees the implicit binding handle defined in
// the IDL file.
if (status)
exit(status);
}
This is the tutorial I followed to develop this project:
Introduction to RPC - part 1
Any reference materials, input or criticism is greatly appreciated.
Thanks for taking the time to read this and for any guidance.

Assuming you are talking about MS-RPC the easy way would be to write an interop DLL in C++ that makes the RPC calls. Have that DLL include the *_c.c and *_h.h outputs of midl.exe and then add code to set up the binding handles etc.
This will require a fair bit of translation in the C++ code (from .net types to types that can go across the wire) but will take the least immediate effort.
More extreme options would be to re-write your RPC code to be pure .net, at that point there are plenty of remoting options available.

Randomly strange behaviour when using select() with timeout on Windows

I'm using a tool to communicate with a gameserver. To establish the connection with the gameserver I'm sending a login packet and then go on from there. I also used a tool, that does the same, but which is written by someone else in C# with a pre-made library. This app has some issues with stackoverflow exceptions after using it for hours and porting it linux isn't much fun aswell, therefore I decided to write my own application from scratch in C++.
My script pretty much looks like this:
while (!connected) {
if (connectCounter == 0)
std::cout << "Trying to connect..." << std::flush;
else
std::cout << "." << std::flush; // add point
connectCounter++;
int selectSize = 0;
struct timeval timeout;
timeout.tv_sec = 5;
timeout.tv_usec = 0;
fd_set fds;
FD_ZERO(&fds);
FD_SET(mysocket, &fds);
selectSize = select(mysocket + 1, &fds, 0, 0, &timeout);
if (selectSize == 1) {
// we might now be logged in, check routines
connected = true;
}
}
Now there's a "bug" randomly happening to me in both applications, the one written by someone else in C# and in my own one. I should probably mention that I've never had this behaviour before, but sinced I formatted my computer I saw this issue happpening for the first time.
Issue: Gameserver was offline for some hours, computer was probably freshly booted. Gameserver is still down and I start the application. Now it tries to login but won't have success as the gameserver is still offline. Now it writes "Trying to connect". Because of the timeout settings it should wait 5 seconds and then add 1 point after every unsuccessful try. Instead it fires point after point without waiting for the timeout. This happens in both application, the C# app written by someone else and in my own application. In both applications it only happens randomly and not every time I'm starting the application. As I mentioned I've never experienced this issues before formatting my computer. I also ported this application to my linux server and didn't not experience that behaviour on linux. A friend of mine also uses both applications and never reported that kind of issue to me.
This is so strange to me and I can't figure out the reason for it. From what I get this can't really be code related because it happens in two totally different applications and from what I can tell only since I reinstalled Windows.
EDIT 1: Now I found something interesting, I added the following code on windows and linux:
selectSize = select(mysocket + 1, &fds, 0, 0, &timeout);
std::cout << selectSize << std::cout;
Interesting thing is that on Windows my console will now output: Trying to connect...0.1.0.1.0.1.0.1
Restarted the application and it outputs Trying to connect...0.0.0.0.0.1
On linux it always returns Trying to connect...0.0.0.0.0, never ever with a false positive.
Still only happening on windows. Don't even know what approach the guy from the C# application used but there it's the same problem happening randomly after reinstalling windows.
EDIT 2: I guess I found the problem.
Before the timeout settings and select() I'm doing a sendto() with my login packet. I guess for whatever reason there is something incoming in return, so that selectSize might change to 1 in some cases. Is it possible that this is causing the issue on Windows, while its working on linux?

Quoting from "the" POSIX specification (a copy of it online):
A descriptor shall be considered ready for reading when a call to an input function with O_NONBLOCK clear would not block, whether or not the function would transfer data successfully. (The function might return data, an end-of-file indication, or an error other than one indicating that it is blocked, and in each of these cases the descriptor shall be considered ready for reading.)
So I'd say in order to fix your code you must additionally check whether file descriptors that are "ready for reading" don't have any error or eof indication.

To check if the socket is connected, you should check it for writability, not readability. Change
selectSize = select(mysocket + 1, &fds, 0, 0, &timeout);
to
selectSize = select(mysocket + 1, 0, &fds, 0, &timeout);

Okay, so it seems that I finally found at least a partial answer to my initial question, why linux gives me a working result while windows breaks my application. From what I have read on windows platforms select() returns WSAECONNECTRESET instead of blocking or timeout, see: WinSock Recvfrom() now returns WSAECONNRESET instead of blocking or timing out
So this seems to be the reason why the application is working perfectly fine (for my purposes) on linux, where select() still seems to return a timeout while Windows returns that error and breaks my application to a certain extent.
Solution:
So I finally found a fix. Special thanks to the guy who reminded me to use Wireshark. At first I tought the select() giving back 1 when it should be 0 after sending the login packet to gameserver while it's offline is totally random but in fact I found out that from time to time I get a "ICMP port unreachable", this caused select() to return 1 instead of 0 (see the link above) Obviously I only want select() to return 1 when an actual login reponse is coming from the sever. On linux this works out of the box and doesn't cause any problems.
For Windows I found a simple fix by adding this code before the select() function:
#define SIO_UDP_CONNRESET _WSAIOW(IOC_VENDOR, 12)
DWORD lpcbBytesReturned = 0;
BOOL lpvInBuffer = FALSE;
WSAIoctl(mysocket, SIO_UDP_CONNRESET, &lpvInBuffer, sizeof(lpvInBuffer), NULL, 0, &lpcbBytesReturned, NULL, NULL);

Can I redirect output from a C DLL into my c# log4net output

I have a C# application which in turn loads a C or C++ dll (which in turn loads other C/C++ dlls). Within the C# application I use a log4net logger to capture all the output into a series of log files. My application runs as a windows service so there is no console/output window for normal printfs or output written into stdout/stderr to go to.
Is there a way to setup the C# application to direct stdout/stderr (from the DLLs) and turn each line into a log4net output. Or is there some way within the C/C++ DLL to connect the stdout/stderr streams to the log4net output?
I found some solution (here : http://bytes.com/topic/c-sharp/answers/822341-dllimport-stdout-gets-eaten) that indicated I needed to put a call into my C DLL like this : setvbuf(stdout, NULL, _IONBF, 0); Though, I don't know what that does, it doesn't do what I want. I assume I'd also need a similar line for stderr. In either case, google seemed to think those lines simply take care of buffering and not redirection into log4net.
I assume I need some sort of function override which snags the console writes (from a loaded DLL in another language) and converts them into mLog.InfoFormat("{0}", consoleString); sorts of calls. I'm new to c# and not even sure what terms to google in order to find such an override (if its even possible).
Not sure if this complicates the problem, but my C# application is multithreaded and some of the DLLs have multiple threads as well. I assume that just means I need a lock of some sort inside the method that handles the console output and writes it into the log4net framework(maybe) or maybe the normal serialization of log4net will handle it for me.

Turns out those did the trick once I figured out how to use them. I setup two named pipes(or two ends of the same pipe?). One I connected to stdout and had it do a log message in log4net of whatever came through the pipe.
internal static void InfoLogWriter(Object threadContext)
{
mLog.Info("InfoLogWriterthread started");
int id = Process.GetCurrentProcess().Id; // make this instance unique
var serverPipe = new NamedPipeServerStream("consoleRedirect" + id, PipeDirection.In, 1);
NamedPipeClientStream clientPipe = new NamedPipeClientStream(".", "consoleRedirect" + id, PipeDirection.Out, PipeOptions.WriteThrough);
mLog.Info("Connecting Client Pipe.");
clientPipe.Connect();
mLog.Info("Connected Client Pipe, redirecting stdout");
HandleRef hr11 = new HandleRef(clientPipe, clientPipe.SafePipeHandle.DangerousGetHandle());
SetStdHandle(-11, hr11.Handle); // redirect stdout to my pipe
mLog.Info("Redirection of stdout complete.");
mLog.Info("Waiting for console connection");
serverPipe.WaitForConnection(); //blocking
mLog.Info("Console connection made.");
using (var stm = new StreamReader(serverPipe))
{
while (serverPipe.IsConnected)
{
try
{
string txt = stm.ReadLine();
if (!string.IsNullOrEmpty(txt))
mLog.InfoFormat("DLL MESSAGE : {0}", txt);
}
catch (IOException)
{
break; // normal disconnect
}
}
}
mLog.Info("Console connection broken. Thread Stopping.");
}
Also have a function to push all that to another thread so it doesn't block my main thread when it hits the various blocking calls.
internal static void RedirectConsole()
{
mLog.Info("RedirectConsole called.");
ThreadPool.QueueUserWorkItem(new System.Threading.WaitCallback(InfoLogWriter));
// TODO enqueue and item for error messages too.
}
I'm having trouble with it disconnecting and have to reconnect the pipes, but I'll figure out a reconnect solution. I'm guessing that happens when DLLs get swapped back out of memory or perhaps when I need to read but there isn't anything currently ready to be read? I've also got to setup another pair to snag stderr and redirect it as well, using Error logs for that one. Probably want to get rid of the magic number (-11) and use the normal enums as well (STD_ERROR_HANDLE, etc)

Generating IntPtr using Convert.ToInt64 failing on x64 applications

I'm trying to use the code from the most popular answer to this question: Using C#, how does one figure out what process locked a file?
I'm testing this code in Windows 7 x64 using VS2010 and .NET v4.
I'm finding that the code excerpt...
var baTemp = new byte[nLength];
try
{
Marshal.Copy(ipTemp, baTemp, 0, nLength);
strObjectName = Marshal.PtrToStringUni(Is64Bits() ? new IntPtr(ipTemp.ToInt64()) : new IntPtr(ipTemp.ToInt32()));
}
catch (AccessViolationException)
{
return null;
}
finally
{
Marshal.FreeHGlobal(ipObjectName);
Win32API.CloseHandle(ipHandle);
}
is what is causing my problems. The Marshal.Copy can fail when the address created earlier is not valid. The code creating the address in x64 systems...
if (Is64Bits())
{
ipTemp = new IntPtr(Convert.ToInt64(objObjectName.Name.Buffer.ToString(), 10) >> 32);
}
in one instance of my noted failures starts with a buffer string representation of 20588995036390572032 that translates to x1C92AA2089E00000. The code appears to strip the low order word leaving x1C92AA20 as the usaable address.
Question 1: Why would we not simply use the 64bit address provided by the buffer object rather than shift out the low order word and use just the high order word in a 64bit app running on a 64bit OS?
Question 2: Should the try/catch/finally block include more than just AccessViolationException?

Read the comments on that article. Unworkable code. Doesn't work. Don't use. Even the "suggested" corrected version is broken (and it doesn't work on my Win8 64bits) and in the words of its author:
The following was produced based on Iain Ballard's code dump. It is broken: it will occasionally lock up when you retrieve the handle name. This code doesn't contain any work-arounds for that issue, and .NET leaves few options: Thread.Abort can no longer abort a thread that's currently in a native method.

Using a SSH library to connect to unix and tail a file: Is this the right approach?

As Ive stated with a few other questions, Ive been using a new SSH .NET library to connect to a Unix server and run various scripts and commands. Well, I've finally attempted to use it to run a Unix tail -f on a live log file and display the tail in a Winforms RichTextBox.
Since the library is not fully-fleshed out, the only kinda-sorta solution I've come up with seems lacking... like the feeling you get when you know there has to be a better way. I have the connection/tailing code in a separate thread as to avoid UI thread lock-ups. This thread supports cancellation request (which will allow the connection to gracefully exit, the only way to ensure the process Unix side is killed). Here's my code thus far (which for the record seems to work, I would just like some thoughts on if this is the right way to go about it):
PasswordConnectionInfo connectionInfo = new PasswordConnectionInfo(lineIP, userName, password);
string command = "cd /logs; tail -f " + BuildFileName() + " \r\n";
using (var ssh = new SshClient(connectionInfo))
{
ssh.Connect();
var output = new MemoryStream();
var shell = ssh.CreateShell(Encoding.ASCII, command, output, output);
shell.Start();
long positionLastWrite = 0;
while (!TestBackgroundWorker.CancellationPending) //checks for cancel request
{
output.Position = positionLastWrite;
var result = new StreamReader(output, Encoding.ASCII).ReadToEnd();
positionLastWrite = output.Position;
UpdateTextBox(result);
Thread.Sleep(1000);
}
shell.Stop();
e.Cancel = true;
}
The UpdateTextBox() function is a thread-safe way of updating the RichTextBox used to display the tail from a different thread. The positionLastWrite stuff is an attempt to make sure I don’t loose any data in between the Thread.Sleep(1000).
Now Im not sure about 2 things, first being that I have the feeling I might be missing out on some data each time with the whole changing MemoryStream position thing (due to my lack of experiance with MemoryStreams, and the second being that the whole sleep for 1 second then update again thing seems pretty archaic and inefficient... any thoughts?

Mh, I just realized that you are not the creator of the SSH library (although it's on codeplex so you could submit patches), anyway: You might want to wrap your loop into a try {} finally {} and call shell.Stop() in the finally block to make sure it is always cleaned up.
Depending on the available interfaces polling might be the only way to go and it is not inherently bad. Whether or not you loose data depends on what the shell object is doing for buffering: Does it buffer all output in memory, does it throw away some output after a certain time?
My original points still stand:
One thing which comes to mind is that it looks like the shell object is buffering the whole output in memory all the time which poses a potential resource problem (out of memory). One option of changing the interface is to use something like a BlockingQueue in the shell object. The shell is then enqueuing the output from the remote host in there and in your client you can just sit there and dequeue which will block if nothing is there to read.
Also: I would consider making the shell object (whatever type CreateShell returns) IDisposable. From your description it sounds shell.Stop() is required to clean up which won't happen in case some exception is thrown in the while loop.