OS is Red hat enterprise linux 5.5 and python version is 2.6
On Feb 2, 4:34 pm, Dennis Lee Bieber <wlfr...@ix.netcom.com> wrote: > On Thu, 2 Feb 2012 05:53:22 -0800 (PST), loial <jldunn2...@gmail.com> > wrote: > > >I am trying to write a python script to read data from a printer port > >using python sockets, but it seems I am locking up the port. > > >Is there a way to ensure that I do not block the port to other > >applications? > > >My knowledge of python sockets is minimal, so any help would be > >appreciated. > > OS and Python version might be of interest... > > However, parallel ports are typically unshared devices (which is why > any multitasking system has things like print spooling -- so multiple > tasks and "print" to the spool, and the spool driver is the only process > actually accessing the printer port). > > I still have nightmares over one assignment I had some 8 years ago: > Reading a clock signal (square wave) on one of the parallel port's > signal pins, in order to time a three-bit /balanced/ (using 6-pins of > the output) data stream. Done on a W98 laptop (since W98 didn't have the > protected ports of WinXP) using Visual C++ -- and on the laptop as the > eventual plan had been to send "red" GPS decryption keys to satellites; > contact with "red" keys makes the hardware it passes through highly > classified, and the main hardware had to stay "open" for uncleared > developers working on flight software. > > Unfortunately, even with the program running at the highest > available Windows priority, the OS still did <something> every few > milliseconds, which led to glitches in the output stream. (The good > news: by the time the DTD with the keys became available, the CONOPS had > changed to use "black" keys, which did not "infect" the computer system > -- so the regular command formatter could be used for uploading). > > -- > Wulfraed Dennis Lee Bieber AF6VN > wlfr...@ix.netcom.com HTTP://wlfraed.home.netcom.com/ -- http://mail.python.org/mailman/listinfo/python-list
