Dos printing problems on Network

Using a dos program that can only print to lpt ports. Printer HP 1200 shared
with paralled cable on PC A. PC B setup the following: net use ltp2
\\pca\hp1200 /persistent:yes.

Most of the time PC B can print dos print jobs to PC A. Sometimes nothing
happens. When we want to run a test print from PC B, we open dos box and
type: dir >lpt2
Normallty this will print a directory listing. When the printing problems
occurs, we get an error message: The system cannot find the file specified.

Please help