Apologies for the duplication. As I understand it, mailslots may be an answer. However I cannot seem to write to one. Create/open okay, but always get "access denied" when writing. If anyone cares, I will post the code.
What I like about mailslots, is that, according to the Windows documentation, the system shuts down the mailslot when the last process using it exits. So (theoretically), if your program crashes, it does not leave an open file or pipe. Untested thought. Might be wrong. The server/listening/TCP solution seems reasonable. Do I understand correctly? (1) There would have to be a server process running on the server machine: call it "appman". So every time an application starts, it would have to ensure "appman" is running on the server. If not, fire it up. (2) The internet classes supplied with Delphi 5 could be used (TServerSocket, TClientSocket). (3) I am not sure how to obtain an IP number and port for this. The ideal situation is done at install time, involves no user knowledge, interaction or config, and does not conflict or destroy any existing settings (hey I can dream can't I?!). Of course there are config overrides for problem installs. But just for the generic simple easy working case, I still have no idea how to proceed getting a workable IP/PORT for this. Current advice is to use localhost 127.0.0.1 and cycle through port numbers above 50000 until an available one is found. Seems kinda flakey to me. But I do not know what I am doing in this regard. Any hints or links greatly appreciated., Thank you. === PS: The recent discussion about a single global variable to track instances may actually be a solution. The program already does this in a much more complex way: session records are created, and these are also used for handling resource conflicts and so forth. The essential difficulty is that I am a stupid programmer, the programs are large and complex, they run on windows networks in real installations... so invariably, an instance will crash. Leaving the session table with orphaned entries. A simple counter program is not so likely to fail. Yet also avoids TCP/IP/mailslots and other windows IPC issues. However. There comes a time when exclusive access to some operation is absolutely required, and the only fail-safe way to ensure every session record is an active one, is to talk to the running sessions. A boring delay is involved as each process must be polled. Cheers [EMAIL PROTECTED] wrote: >> Happy New Year! >> Delphi 5 >> Windows local area network. >> How do I determine if any other instances of my EXE are running on the network? >> Each is started from the same common folder. >> My program already manages a "session table". But sometime my program fails and exits abnormally, so the session table entry does not get deleted. >> I wish for a routine that would poll or otherwise determine somehow "in real time" if there are truly active instances of the same EXE alive on the network. >> Not sure which set of windows API calls I should be looking at. Many thanks in advance. > > Haven't we already answered this question or something like it before? > > There is no Windows API to do what you want. The only way you can come close would be to have a central server that all instances of your EXE connect into - probably over TCP/IP. Then you can send whatever data you want over the connection as long as the server handles it. Throw in some sort of keep-alive that gets sent every 30 seconds or so to keep the underlying socket from disconnecting. Then when you want > information in "real-time", you connect into the server with a special application that retrieves the client information via a broadcast of some sort to which clients respond and the server collects and sends to the special client. > > That's the only way I know of to get close to getting real-time responses.
