Environment: Windows NT 4 SP5, Visual C++ 6 SP2
In a recent project that uses an IPX protocol for communication between multiple
Windows NT stations and multiple DOS stations, I needed to find out the IPX
node address of the local computer as well as the node addresses of all computers
on the network (running under Windows or DOS). So, I designed 2 programs (one
32 bit for Windows and the second 16 bit for DOS) that support the same custom
packet type. The final result is an application that shows the node address
of each computer in a network that is running either one of the programs together
with the local time on each computer.
On DOS side, I am using a direct interrupt call to IPX/SPX driver installed
on a DOS machine. On Windows side, I am using Winsock 2 API for IPX communication.
Setting up initial communication was a bit complicated but the final code is
very simple.
The idea is the following: Each application is running under a timer. When
timer expires (1 second), the application broadcasts a packet with its local
time and its user defined name. This broadcast packet is catched by all stations
(including the sending station) and is displayed in a list. If it already exists
in a list, the list item is updated. Since this is a connectionless communication,
technique for obtaining the sender’s IPX node address is different for DOS and
Windows. DOS code directly takes the sender’s node address from the IPX packet.
However, since Windows application is using Winsock 2, access to packet structure
is not available. Within a Winsock window message handler, application executes
a recvfrom() function call that returns a node address of the sender.
These 2 applications proved to be very useful since one can obtain all the
node addresses but also (and this is very important) can check whether the support
for IPX communication is installed on the machine (either Windows or DOS) and
check whether the IPX communication is running correctly (even if all is ok,
stations may be invisible to each other if an Ethernet frame type is not the
same). So, these 2 applications are also a good diagnostic tools.
I plan to work on the same application (only Windows version) that supports
the TCP/IP protocol (actually only IP since it is going to work using an UDP
protocol). You can check for the latest info on www.scasoftware.com.