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

Question

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

events.js:183
      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-
Samples\Node\cards-AdaptiveCards\node_modules\restify\lib\server.js:404:32)
    at Object.<anonymous> (C:\Users\yu\Documents\GitHub\BotBuilder-
Samples\Node\cards-AdaptiveCards\app.js:10:8)
    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    0.0.0.0:3978           0.0.0.0:0              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

Answer 1

If you are on mac, to make sure nothing is running on the same port, do:

killall node

and restart your app.

Answer 2

The port you are listening to is already being listened by another process.

When I faced to this error I killed the process using Windows PowerShell (because I used Windows)

1. open the windows powershell
2. type ps and then you can get list of processes
3. find the process named node, and note the Id
4. type Stop-process <Id>

I think that it is help for windows users.