还真的是， 谢谢老大！

为什么 terminal 会出现：
events.js:183
throw er; // Unhandled 'error' event
^

Error: listen EADDRINUSE 127.0.0.1:3000
at Object._errnoException (util.js:992:11)
at _exceptionWithHostPort (util.js:1014:20)
at Server.setupListenHandle as _listen2
at listenInCluster (net.js:1396:12)
at doListen (net.js:1505:7)
at _combinedTickCallback (internal/process/next_tick.js:141:11)
at process._tickCallback (internal/process/next_tick.js:180:9)
at Function.Module.runMain (module.js:695:11)
at startup (bootstrap_node.js:191:16)
at bootstrap_node.js:612:3

svg 的应用