Dear list: We have just supped with the devil - written part of a software contract in Window$ NT - the display part not the functional part which is DOS of course.
The overview program in NT gets talked to by datagrams from the DOS part over an ethernet. This we think an adequate firewall! Our "interesting" discoveries about NT are .... At this point James got a bit excited and took over: 1/ My NT installation got virused from Win95 - 'Bride' & 'W95/funlove'. The W95 was recovered but the NT thing died, and refuses to let me reinstall it !. We did get to try 'VirusScan' on the NT machine, albeit and old copy, and it failed to detect anything wrong, even though 'Command' virus software could see the problem over the network. 2/ The free Borland compiler required a 30Mb download for service pak 4 - we got 6a. 3/ The Rail Authority supplied a machine in order to eliminate compatibility issues. We installed NT4 & upgraded it - nothing else - and were rewarded for our efforts with a 'Blue Screen of Death'. Reinstalling the stuff has retained the old crashed stuff if the bottom two from the boot menu are selected. I know about the file that controls this, but have forgotten the filename .... anyone? So, we can boot into a crashed partition at will ! 4/ This new NT system has not had any weird software loaded or games, just essential stuff - Ftp, compiler, Acrobat, WinZip. And never connected to the internet.So it should be safe, yeh ? 5/ One day, booting up showed the editors in the compiler stuffing up keywords. These are shown in bold text, and only the first letter of these keywords was displayed. Further inspection revealed the other letters 'randomly scattered' over the screen, not merely limited to the operating windows ! Taking out the first character caused the rest of the keyword to be displayed again ( no longer bold), but clearly not usable for the software ! Later, this problem came up in Notepad. Yes A simple, dumb text processor. I put large fonts on it one night to show my visually impaired partner (bold !), and in the morning I tried to look at the file. It came up very screwed up - put text over the toolbar, and crashed the machine severely back to initial BIO bootup. This was quite repeatable. With one month to delivery, I was quite impresed by this :-( So I tried a few things - Yes, the internal network was ok, and the OS/2 machine could read the files without drama. No doubt arachne also would have been ok using epppd. So it was not a file/retrieval problen, just a display one. So how does a dumb display program acheive a total crash ? It appears that some fonts break the system. Good effort, Bill ! Udp to the Win NT4 machine was also interesting. Now, as you know, Udp is a blind 'we sent it, the problem must be at your end' kind of guy, so it should be very simple. Not so. Observing the data packets with a packet analyser, we observed that for the Win NT4 machine to send Udp, it first sends an ARP to the designated IP, which returns it's MAC address so that the NT4 machine can finally send. Now, if the machine can send a 'blind' ARP' packet to another machine, why cannot it not just UDP and be done with it ?. Well, as usual, the trick bag was brought out to play. Using the broadcast address, the MAC address of the destination is no longer unique, it can be ignored. One sidestep. So, as we only needed the NT4 machine to listen, we thought, no worries. Again, the above symptom & method were required. Now, if a full packet interface is achieved, this does not matter as it it is handled by the program. The DOS program, however, is now getting fat (500k), and room for dynamic data is at a premium. Therefore, we only implemented transmission of Udp packets. Which led us to the above techniques to avoid having to implement ARP. We 'could' have hard coded MAC addresses, but this is pretty poor form. What fun. Soon, I shall deliver, and then I can get some sleep. But I am a bit concerned that it may prove difficult to keep an NT4 machine going so that warranty work can be carried out.... I should have written it in Linux, but the customer ..... Slightly off-topic ....Kali & James http://www.nimnet.asn.au/~kali
