Take --debug-port into account

lib/_inspect.js

@@ -41,7 +41,16 @@ const [ InspectClient, createRepl ] =
 
 const debuglog = util.debuglog('inspect');
 
-exports.port = 9229;
+const DEBUG_PORT_PATTERN = /^--(?:debug|inspect)-port=(\d+)$/;
+function getDefaultPort() {
+  for (const arg of process.execArgv) {
+    const match = arg.match(DEBUG_PORT_PATTERN);
+    if (match) {
+      return +match[1];
+    }
+  }
+  return 9229;
+}
 
 function runScript(script, scriptArgs, inspectPort, childPrint) {
   return new Promise((resolve) => {
@@ -228,7 +237,7 @@ class NodeInspector {
 
 function parseArgv([target, ...args]) {
   let host = '127.0.0.1';
-  let port = exports.port;
+  let port = getDefaultPort();
   let isRemote = false;
   let script = target;
   let scriptArgs = args;