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Using Named Pipes for Tracing

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14 Jul 20042 min read 77.1K   3.8K   49   6
Using Named Pipes for Traces out of Multiple Processes


Traces are very useful tools for debugging purposes, especially if the program runs as a release version. It is easy to save the traces for a single application. But it needs a little work to receive the traces of multiple processes or even threads running at the same time in one single file or window. The example given here describes an elegant way to solve this problem. It uses "named pipes" for interprocess communication. Each process sends its trace data to one central special listener process. For the processes sending traces it doesn't matter if this listener process does or does not exist.


A Named Pipe is a high level mechanism for the communication between processes even if they are running on different computers linked by a network. It hides all the communication details and offers two sides: One side to put data in and one side to read it out, but it can also be used bidirectional.

For building up a communication line, a process creates a pipe with a unique name. Using this name another process can connect to this pipe. Because a named pipe is a link between only two processes, it needs a set of named pipes to communicate with more then two processes at the same time. Each instance of these named pipe can use the same name.

The reading or writing of data to a pipe can be done with the normal set of Windows commands used to read or write data to a file. Like the normal file operations named pipes can be accessed in a blocking (= synchronous) or nonblocking (= asynchronous) mode. This example uses the synchronous communication mode because it is especially simple to use: The function calls to read or write data don't come back until the communication operation has finished. To allow communication with multiple processes it uses one thread for each pipe. Every time a new process connects to the listener, it creates a new pipe allowing the next process to connect with.

Using the code

For sending a trace, there is just a very easy interface needed: Building up the communication with Connect and sending traces with MakeTrace. The usage is demonstrated in the simple dialog based application TraceSender. You may start multiple instances of this program to generate more traffic.

class CTracer  
  virtual ~CTracer();

  bool Connect();
  bool MakeTrace(const char* pStr,...) const;    // use like printf(...)

  HANDLE m_hPipe;


Because of its multithreading capability the mechanism for receiving traces is a little bit more complicate to implement. But its usage is as simple. This demonstrates the simple console application TraceListener:

#include "stdafx.h"
#include "conio.h"

#include "TraceCollector.h"

BOOL OnTrace(const char* pStr, DWORD nLength)
  return TRUE;

int main(int argc, char* argv[])
  CTraceCollector tracer(OnTrace);

  return 0;


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Comments and Discussions

Generalall pipe instance are busy GetLastError() = 231 Pin
rahulagarwal3313-Oct-08 5:37
rahulagarwal3313-Oct-08 5:37 
GeneralExactly what I was looking for! Pin
mi-chi23-Sep-07 19:44
mi-chi23-Sep-07 19:44 
GeneralPossible handle leak Pin
Jim Xochellis10-Oct-06 22:58
Jim Xochellis10-Oct-06 22:58 
GeneralGlad you exist! Pin
philFox15-Mar-06 17:09
philFox15-Mar-06 17:09 
Generalthanks Pin
Moak1-Jul-05 0:41
Moak1-Jul-05 0:41 
GeneralTwo Words Pin
Brad Bruce15-Jul-04 6:47
Brad Bruce15-Jul-04 6:47 
Awe Some OMG | :OMG:

Just what I needed. I'm trying to communicate from a service to an app that I have written and wanted to get away from sockets!!!!!

Good Work

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