fix getPort by use a well-tested npm module

package.json

@@ -84,6 +84,7 @@
     "memory-card": "^0.6.9",
     "npm-programmatic": "0.0.11",
     "pkg-dir": "^3.0.0",
+    "portfinder": "^1.0.17",
     "promise-retry": "^1.1.1",
     "qr-image": "^3.2.0",
     "raven": "^2.6.2",

src/helper-functions/impure/get-port.spec.ts

@@ -25,8 +25,6 @@ import net from 'net'
 import { getPort } from './get-port'
 
 test('getPort() for an available socket port', async t => {
-  // const PORT = 8788
-
   let port = await getPort()
   let ttl = 17
 
@@ -37,7 +35,7 @@ test('getPort() for an available socket port', async t => {
       const server = net.createServer(socket => {
         console.log(socket)
       })
-      server.listen(port, '127.0.0.1')
+      await new Promise(r => server.listen(port, r))
       serverList.push(server)
 
       port = await getPort()

src/helper-functions/impure/get-port.ts

-import net     from 'net'
-
-const DEFAULT_PORT = 38788
+import portfinder from 'portfinder'
 
 /**
  *
@@ -13,47 +11,11 @@ const DEFAULT_PORT = 38788
  * const DEFAULT_IANA_RANGE = {min: 49152, max: 65535}
  *
  */
-export function getPort (port = DEFAULT_PORT): Promise<number> {
-  let tryPort = nextPort(port)
-
-  return new Promise(resolve => {
-    // https://gist.github.com/mikeal/1840641
-    function _getPort (cb: (port: number) => void) {
-      const server = net.createServer()
-      server.on('error', (err) => {
-        if (err) {/* fail safe */ }
-        tryPort = nextPort(port)
-        _getPort(cb)
-      })
-      server.listen(tryPort, (err: any) => {
-        if (err) {/* fail safe */}
-        server.once('close', () => {
-          cb(tryPort)
-        })
-        server.close()
-      })
-    }
-    _getPort(okPort => {
-      // put to the end of the event loop
-      // make sure that all tasks had been done, esp. server.close()
-      setImmediate(() => resolve(okPort))
-    })
-  })
-
-  function nextPort (currentPort: number): number {
-    const RANGE = 1733
-    // do not use Math.random() here, because AVA will fork, then here will get the same random number, cause a race condition for socket listen
-    const n = Math.floor(Math.random() * RANGE)
-
-    /**
-     * nano seconds from node: http://stackoverflow.com/a/18197438/1123955
-     */
-    // const [, nanoSeed] = process.hrtime()
-    // const n = 1 + nanoSeed % RANGE // +1 to prevent same port
-
-    if (currentPort + n > 65000) {
-      return currentPort + n - RANGE
-    }
-    return currentPort + n
+export async function getPort (
+  basePort?: number,
+): Promise<number> {
+  if (basePort) {
+    portfinder.basePort = basePort
   }
+  return portfinder.getPortPromise()
 }