>>>How can I send something from the command line in DOS to a port to see if it is being received on the other end? Thanks!
>>
>>Check http://www.vfrazee.com/ms-dos/6.22/help/copy.htm
>>
>>However, I do not see an easy way to capture output into extra file, as you can do with > for some commands. Or at least it's not mentioned in this page.
>
>I'm not sure if this is exactly what I'm looing for. I just want to see if a port is really listening. DOS NetStat says that it is ESTABLISHED, but I want to see a text string to come through as a check.

NetCat may do what you want. Might take some playing around (on both server and client ends) to actually see a string being passed. http://en.wikipedia.org/wiki/Netcat

Tools such as NetCat and NMap are often used as hacker tools, and may be detected and removed by antivirus programs.