I made a change to my software, and suddenly the Ethernet is dead. It seems to send and receive nothing.

I back out my change, and it still doesn’t work.

I back out a few more: no effect.

As it turns out, one of the Ethernet switches got confused and quit routing correctly (even through this simple configuration).

You can tell that the switch has some smarts:

• When you look at the traffic with WireShark, you don’t see what’s exchanged between the switch’s other nodes.
• When you have a mix of GB devices and 10MB devices on the same switch, the gigabit devices transfer data at full speed, so you know the switch isn’t exposing every packet to every (10MB) connection.

Still, I was astonished that this could happen.

For the record, the switches were:

• Netgear ProSafe 5 Port Gigabit Switch (Model GS105)
• Netgear 4-Port 10/100 Dual Speed Hub (Model DS104)

The older DS104 was the prime suspect. I simplified the route to just one switch (the GS105), which got it working. So I cycled power on the DS104, reconnected the original configuration, and everything worked again.

Update 4/8: They say you never learn anything from a mule’s second kick. I unceremoniously decommissioned the DS104 after it did the same thing again, this time with no provocation.

Cause: 255.255.255.255 is too general. TangentSoft has the general solution (implemented in boost). I craft the broadcast address more carefully, and it works.

	10.x.x.x (subnet 255.0.0.0) => 10.255.255.255
	192.168.1.x (subnet 255.255.255.0) => 192.168.1.255

It’s not the language or library. It’s seen for C#, C, and C++, etc, on Windows Vista, and here.

The broadcast address 255.255.255.255 is also known as INADDR_BROADCAST or ‘‘ in Python.

You only need one socket, which you can bind to all interfaces.

Enumerating your network interfaces requires some work: find it under Win32_NetworkAdapterConfiguration, fields IPAddress and IPSubnet. Those fields are arrays: you want element zero.

If you’re using python, you need the WMI package, which is built on the PyWin32 package.

import wmi
nicsList = wmi.WMI().Win32_NetworkAdapterConfiguration() # your network adapters

If you’re getting WinSock error 10013, you need to set SO_BROADCAST.

Hope that starts you down the right path.

Also, if your devices aren’t configured for the same subnet, crafting a sub-net-specific broadcast message means you’re not going to find them. For example, if you have a 10.x.x.x device off your 192.168.x.x interface, it’s going to ignore your 192.168.255.255 broadcast. You’ll have to fall back to disabling a network interface and using 255.255.255.255 to get to it.

Very interesting that C seems to be such a constant. And far more constant even than its second place suggests, since six of the top eight languages use a syntax based on it (Java, PHP, C++, C#, and JavaScript), not to mention Objective-C. C is the bedrock.

Objective-C seems to be coming on crazy strong. It has been around forever, but Apple’s interest is giving it a boost. Apple’s interest alone, though, will only get it so far.

Java and C# are here to stay, and for good reason. They’re strongly typed, object oriented, have great libraries and manage some of the hard stuff for you.

C++, my language of choice, seems to be slipping. I’m not concerned. I’m convinced that the C++ compiler is the most powerful software development tool ever. When managing complexity and maximizing performance are crucial, C++ is it.

I’m glad Python is doing well. It’s a great scripting language with a great set of libraries. I think it’s overcoming Perl’s passionate and loyal following. (I admit: one of my career goals is avoiding learning Perl. And I think I just might make it.)

JavaScript is crucial to know, too: every browser runs it. It’s as ubiquitous as the web.

For the record, my proficiencies, in my best-guess order: C++, C, Java, C#, Python, JavaScript, Visual Basic.

PS: The TIOBE Index isn’t to be taken as gospel.

Methodology, strategy and work-flow all rolled into one rather informal process. Not specifically for software projects, either.

I believe OOP is the very best way to manage complexity, but isn’t the end-all be-all. It must build on structured programming techniques. That’s not a given.

Further, memory organization may make a big difference as well, depending on the application. Even with modern processors and gigabytes of RAM. I recently encountered an application that needed its memory footprint to be reworked. It brought the very-powerful machine on which it ran to its knees by using memory very inefficiently.

Though I don’t have much desire to build games, I appreciate the game-development community. They build incredibly ambitious pieces of software: ambitious in both complexity and performance. That causes them to encounter many issues one might not consider, and think hard about everything they do.

Update: Here’s a very detailed article on memory usage from the bare metal up: What Every Programmer Should Know About Memory, by Ulrich Drepper. Hat-tip Dan DeMaggio. If your performance concerns reach all the way to RAM access and CPU caches, this is one to study. It’s a whole course, and not a light read. One take-away: memory usage patterns can have very non-linear effects on performance.

My MinGW/MSYS configuration is with the full suite of tools, including bash. (Follow these FFmpeg build instructions for setup.)

As well, I’m using GCC 4.3.3, from the TDM recent builds (http://www.tdragon.net/recentgcc/) setup.

I’m building OpenSSL 0.9.8k.

You need ActivePerl. MinGW has a /bin/perl, but it’s not up to the task. See OpenSSL’s INSTALL.WIN32 file for details.

From a Win32 command prompt (not bash), set up the your paths:

• First in the path: ActivePerl’s bin directory.
• Then MinGW’s paths (before Win32 native).

Fix the file e_os2.h, per BUG 1685. Remove the “static” modifier in the OPENSSL_IMPLEMENT_GLOBAL macro. (Note that it’s a 3-line macro.) This gets you by the “crypto/des/set_key.c line 72″ compile error.

Run ms\mingw32.bat. It will fail with “/bin/sh: copy: command not found”.

Now, edit the file ms\mingw32a.mak. This gets generated by every run of the ms\mingw32.bat file. Search for “exist” and you’ll see two DOSish commands:

if exist $(O_CRYPTO) ] $(RM) $(O_CRYPTO)

Change each to its bash equivalent:

if [ -e $(O_CRYPTO) ]; then $(RM) $(O_CRYPTO); fi

Finally, run the make, and specify the MinGW copy command:

make -f ms/mingw32a.mak “CP=cp”

The output files are in the ‘out’ subdirectory. Intermediate files are in ‘tmp’.

Include files are in ‘outinc’: the include/openssl directory has zero-byte place-holders for each file.

Make’s “clean” and “test” targets are broken. To clean, remove tmp and out. To test, run the various test programs in the ‘out’ directory.

All tests pass.

If you get missing symbols like DeleteDC and send when linking against libcrypto, you’ll need to include some win32 libraries. This typically does it:

make LIBS=”-lgdi32 -lws2_32″

Unless you know it’s right, you don’t know it’s right.

To ponder…

What’s your most controversial programming opinion?

(Via Gadgetopia.)

I get some of my best ideas when I step away from the computer for a few hours and carry on with life (letting the problem mull over in the back of my mind). Maybe you’ve experienced this, too.

If software is much more about good ideas than BFI (and I’m convinced that it is), then stepping away from the computer is a wonderful thing all around.

It’s interesting how many programs now come up underneath it. Commercial packages with large user bases. I’m sure they mind the task bar when it’s at the bottom of the screen, but not here.

While it’s not a big deal (to me at least–just a tiny annoyance), it shows how we make implicit assumptions about our world. Sometimes those assumptions are fine. Sometimes not.

I’ve made plenty myself.

Also, I’ve not encountered a program that refuses to run or throws itself off the top or bottom of the screen because of this. That’s a possibility. (I need to keep this in mind if I find a program behaving badly with its screen position.)