How do I determine the identity of a Windows machine?

Question

I have a program consisting of a server and a client processes. Both run on Windows systems - Windows 2000 or later versions. The two processes can run on the same machine or on two different machines.

How can the client determine if it is run on the same machine as the server? If the server is not running the client can't work anyway and doesn't care where the server possibly is - so this case is out of the question. I've heard that each Windows machine has an UUID - can I obtain it and use for that purpose?

Answer 1

how about trying to establish a loopback tcp connection? or maybe checking for some lock file created by the server in a predefined folder...

I don't know exactly how, but there's for sure something equivalent in Win32 to the /proc filesystem in Unix (I think there are free replacements for the windows taskmanager, maybe you could look at their sources) where you could search for your server process.

Answer 2

Previous question about generating a unique machine id that might help. Link to previous answer which mentions MachineGUID

It is straightforward to add an API to the server that reports its machine name. The environment variable is COMPUTERNAME. The client could check that, right?

Do you need to deal with any of these cases?

1. The client is running, but the server is not responding, and you want to know whether the unresponsive server is on a remote machine.
2. The client and the server are running in two distinct virtual machines on the same host machine, and you want to report that as "running on the same machine."
3. The client is running in a virtual machine hosted by the same machine as the server is running on, and you want to report that as "running on the same machine."
4. The client and the server are running on uncoordinated networks and both might have been assigned the same name.
5. The server is possibly hostile, and will attempt to deceive the client.

The network card will have a unique MAC. If both server and client report the same MAC then they are using the same network card. If both client and server are running in different virtual machines but using the same network card, do you consider them running on the same machine or different machines?

Answer 3

Windows networking requires computer names to be unique, so calling the GetComputerName api and having the client and server swap names (and compare the received name to the name they see) should suffice. If the client and server can start up independently of one another then you'll need some sort of protocol for this process. It seems logical for the client to initiate the exchange, and the server to only send its name when it has received a name from a client. The client can then abort the connection if it sees the same name.

I believe most virtual machine systems will allow the virtual machine to have its own name, so it should still be possible for you to test on virtual machines. However I don't have extensive experience of all the virtualisation technologies out there, so can't say for sure.