node.js error message events.js:183 throw er; // Unhandled ‘error’ event

Playing around Microsoft’s botframework, when I try to run the app.js file, which is the main file of the bot, the first time is fine, after I close the bot emulator, and all programs, and run the app.js again, this error message pops out

      throw er; // Unhandled 'error' event

Error: listen EADDRINUSE :::3978
    at Object._errnoException (util.js:1022:11)
    at _exceptionWithHostPort (util.js:1044:20)
    at Server.setupListenHandle [as _listen2] (net.js:1351:14)
    at listenInCluster (net.js:1392:12)
    at Server.listen (net.js:1476:7)
    at Server.listen (C:\Users\yu\Documents\GitHub\BotBuilder-
    at Object.<anonymous> (C:\Users\yu\Documents\GitHub\BotBuilder-
    at Module._compile (module.js:643:30)
    at Object.Module._extensions..js (module.js:654:10)
    at Module.load (module.js:556:32)

I found some solution to this, It looks like the port 3978 was taken when I run the js file for the second time, and I have to use cmd to find which task is using that port, and then kill the task.

C:\>netstat -aon|findstr 3978

so this one is taking the port, although I already closed all programs

TCP               LISTENING       13140
TCP    [::]:3978              [::]:0                 LISTENING       13140

actually it is node.exe itself, it still running at background

C:\Users\yu>tasklist|findstr 13140
node.exe                     13140 Console                    1     42,064 K

and I need to kill it

C:\Users\yu>taskkill /f /t /im node.exe

Is there a way to not always repeat doing this when I want to run the file more than one time, it just starts to go wired today, and I mean for all different app.js files, include offical sample code. For the past one month, everything was fine, the IDE I am using is sublime text 3, node.js version is 8.9.4 lts

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