Progress on preventing multiple instances of a program from running in windows

[thierry]

Hi,

LJ> Hello... the following script seems to work.

LJ> Factors to consider:
LJ> 1)The stack should be set to purge itself from memory upon closing
LJ> 2)Some firewalls might prevent the program from accepting
LJ> connections on a port
LJ> 3)This prevents multiple instances, but still does not quite allow
LJ> the two instances to communicate. Writing to a socket from one instance
LJ> seems to steal the ability of the other instance to listen to that
LJ> socket - I am still trying to work out how to do that.

humm, with my little experience, you probably need to differenciate the 1st
instance from the second. if the first do a accept connection ( Server mode )
the second instance should do a connect as a client. So, if you see yourself
in the netstat result then run a open socket on the port.

LJ> 4)You might want to consider hiding the windows console and
LJ> setting the cursor to watch while the script performs the shell command.
LJ> 5)This will not work with the opensockets function, because that
LJ> does not return the sockets opened by the other instance. The shell
LJ> command for this works quite well (at least on my computer).

LJ> Cheers,
LJ> Jonathan


LJ> on preopenstack
LJ>   get shell("netstat -a")
LJ>   put it into OPS
LJ>   put the number of lines in OPS into Z
LJ>   set the itemdelimiter to ":"
LJ>   repeat with X = 1 to Z
LJ>     put word 2 of line X of OPS into WPS
LJ>     if item 2 of WPS = "48953" then put "open" into queryold
LJ>   end repeat
LJ>   if queryold = "open" then
LJ>     answer "This program is already running, do you wish to run another
LJ> instance of it?" with "No" and "Yes"
LJ>     put it into AAA
LJ>     if AAA = "No" then 
LJ>       close this stack
LJ>     end if
LJ>   else
LJ>     accept connections on port 48953 with message "queryinstance"
LJ>   end if
LJ> end preopenstack

Running get shell("netstat -a") , i got this on a Win98 box :

Active Connections

  Proto  Local Address          Foreign Address        State
  TCP    xxxxx:1068             0.0.0.0:0              LISTENING
  TCP    xxxxx:2530             0.0.0.0:0              LISTENING
  TCP    xxxxx:1068             127.0.0.1:2530         ESTABLISHED
  TCP    xxxxx:2530             127.0.0.1:1068         ESTABLISHED

  what i don't understand is that i do only one <accept connection>,
  and then only one external process read the socket. So, why this
  4 lines ?


Regards, thierry