I know you're thinking, "Um, duh!" but...

I'm opening a port for listening by using the following:

.tcpServer.Object.LocalPort = m.Port
.tcpServer.Object.Listen

That port remains listening until... When?

UPDATE: The real issue is that once something is sent from a 3rd-party app to the port, it doesn't seem to be able to send again.

UPDATE2: This page had some possibly relevent, but I'm not sure if it really is: http://www.netbook.cs.purdue.edu/othrpags/qanda148.htm

Primarily:

A: That's unlikely. It's more likely that the application on B does not close (or shutdown) the socket after receiving the end-of-file. If your hypothesis was correct, side B would remain in the LAST ACK state instead. 

There is one other possibility: TCP has been implemented incorrectly. It could be that when a process is killed, TCP does not shutdown the control block correctly, meaning that it will fail to send an error message (RESET) 

Do I need to have my listening service to close the socket after receiving the information? How do I know what the information being sent is done?