Pick an available port instead of crashing with "listen EADDRINUSE"

[markhilton]

DEBUG INFO: webtorrent 0.60.1, node v0.12.7, darwin x64, exit 1
events.js:85
throw er; // Unhandled 'error' event
^
Error: listen EADDRINUSE
at exports._errnoException (util.js:746:11)
at Server._listen2 (net.js:1156:14)
at listen (net.js:1182:10)
at Server.listen (net.js:1267:5)
at runDownload (/opt/local/lib/node_modules/webtorrent/bin/cmd.js:313:10)
at Object. (/opt/local/lib/node_modules/webtorrent/bin/cmd.js:147:3)
at Module._compile (module.js:460:26)
at Object.Module._extensions..js (module.js:478:10)
at Module.load (module.js:355:32)
at Function.Module._load (module.js:310:12)

[feross]

This error means that the port WebTorrent wants to use (port 8000) is already in use. This could be from an other instance of WebTorrent, or any another program.

You can run WebTorrent on a different port by using the --port argument:

webtorrent --port 8001

I'll leave this issue open since we can do better here -- by either providing a friendlier error, or preferably, automatically picking an available port.

[markhilton]

Thanks!

[feross]

Leaving this issue open until we support automatically picking an available port instead of crashing.

[Stiveknx]

@feross I'm whiling to help on this.
It's ok to use an external package for that?
(I think it would be too much work doing this without).

https://github.com/baalexander/node-portscanner

[gillesdemey]

@Stiveknx It's not too much work actually, it can be done in just a few lines of code.

https://github.com/gillesdemey/grop/blob/master/index.js

There are countless modules on npm already, though it looks like node-portscanner has a few more bells and whistles.

[feross]

@Stiveknx Cool, happy to accept a PR from you that implements this. You might not need to use an open port finder, but instead pass 0 in as the port so the OS will automatically pick an available one.

@gillesdemey grop is a module done right – looks nice.

[yciabaud]

I made a little contribution on this, I believe this is what you were talking about...
Let me know if there is anything.