ABSTRACT.TXT

MTTTY: Multi-threaded Terminal Sample (Win32)

MTTTY illustrates overlapped serial communication
using multiple threads.

MTTTY is a companion sample for the "Serial 
Communication in Win32" technical article 
in the Microsoft(R) Developer Network Library.

MTTTY was built and tested under Microsoft Windows(TM) 
95 and Microsoft Windows NT 3.51 using Microsoft
Visual C/C++ version 2.0 and the combined Win32 SDK
for Windows 95 and Windows NT.

How it works:

The program utilizes 3 threads.  A main thread initializes the comm
port and maintains the user interface while two working threads
do all the serial communication work.

A reader/status thread is created to handle port reading and to 
monitor status events.  The thread issues an overlapped read
operation and an overlapped status operation.  When one of 
these operation completes, it is handled and information is
imparted to the user.  If a timeout occurs waiting for an operation
to complete, background work is performed.

A writer thread is created to accept output requests and send them
out the comm port.  The writer thread utilizes a work queue.  Each
output request is placed on a linked list in a private heap and a
syncrhonization event is signaled to indicated new work.  When the
writer thread is available to do work, it will retrieve the
output request and perform the output.

Caution:

This sample utilizes multiple threads only for the sake of simplicity
and performance. A more efficient method for this program might 
be to have a single thread perform all i/o requests and then 
wait on multiple handles for each operation to complete.  
Creating multiple threads just for the sake of simplicity
in a full blown application may not be best implementation.

I chose the model for reasons specific to file transfer.  I wanted
reading and writing to be completely separate operations not dependant
on each other in any way.


KEYWORDS: MTTTY