A multi-connection AFD-based echo server

Last time I looked at way of using \Device\Afd to perform individual socket polling for readiness. This differed from the previous approach to using \Device\Afd, which batched up the sockets and issued a single poll for multiple sockets. The individual socket polling approach appeals to me as it would appear to scale more easily, and putting together an echo server that supports multiple connections is now much easier. It doesn’t map as well to the way other operating systems do things though, so if that’s your primary goal, then you’re probably better off continuing with the ‘set of sockets’ approach.

Socket readiness without \Device\Afd

Recently, I’be been exploring socket readiness notifications on Windows using the \Device\Afd interface. My initial forays into this were from a Linux epoll direction as the use of the \Device\Afd API provides a similar interface to the epoll API and makes it possible to build something almost the same on Windows which can help when writing cross platform code. I’d got to the point where I had a simple client and server working nicely and had taken a pause before the next step which was to add support for multiple sockets.

Visual Studio solution files with unix line-end crash explorer...

I’ve just had to deal with a situation where Windows 11 Explorer crashes and restarts every time I browse to a particular directory. The directory contained the source to my AFD code and I somehow managed to guess at the cause and fix the offending file… The problem was that I had some Visual Studio sln files checked in to a git repository and at some point git had changed the line ends from windows \r\n to unix \n.

More \Device\Afd goodness

For a while now I’ve been playing around with the low-level access to the Windows networking stack that is provided by \Device\Afd. Recently I had a comment from a reader, Matt James, who pointed me in the direction of his work over at https://github.com/Emjayen/napi which does a lot more with the \Device\Afd interface than I have. It’s well worth checking out. This code includes, as reference, a set of NT Native API headers from the Process Hacker project, which in itself is interesting stuff, but Matt’s code goes far beyond my megre investigations and provides enough information to produce a full featured network API that appears to be able to everything you might need through the \Device\Afd interface.

Asynchronous Events: Bug in OOB data handling

There’s a bug in the TCP OOB (out of band) data handling code in all versions of The Server Framework from 6.6 through to 7.4. This issue manifests as a purecall during socket destruction and is due to a race condition during the release of the last two references held on a socket. If you don’t use OOB then a simple work around is to comment out the following in TAsyncSocket.

Debugging yourself...

Recently I spent quite a long time debugging a heap corruption bug. When I eventually found the issue, it was such a classic buffer overrun bug that it was actually quite laughable how long it had taken to track it down. It was just SO obvious that I immediately spotted it as soon as I looked at the code. The problem was that it took me so long to actually look at this piece of code.

The US government's view on memory safe code is not the whole story

There’s a lot of noise about how “Joe Biden’s government wants you to move away from using C++”. This is as a result of the US government releasing a report, Back to the building blocks: A path toward secure and measurable software which suggests: Uncle Sam says "no!" “Memory safety vulnerabilities are a class of vulnerability affecting how memory can be accessed, written, allocated, or deallocated in unintended ways. Experts have identified a few programming languages that both lack traits associated with memory safety and also have high proliferation across critical systems, such as C and C++.

MiniDumpWriteDump now mostly useless for in process use

I’ve been using the MiniDumpWriteDump() API from DbgHelp.dll for 20 years or so. It has proven to be a useful diagnostic tool, and I use it in all manner of places, including many where others may simply use an assert(). It’s a heavy-weight debugging tool, but it has proved useful over the years; rather than just throwing an exception because things that shouldn’t happen have happened, I often also generate a dump file so that I can get far more data than you could ever log or report in another way.

Old and cranky me from 20 years ago

Back in 2004 I wrote this, I wonder why I used to make some people unhappy… I’m starting to believe that, at 37, I must now be old and cranky because to be quite honest with you; if you’re not writing code in such a way that you define concepts and abstractions in such a way that the actual main line business logic code that you write is clear and easy to understand then you’re just not doing it right.