added debug info in readme, range debug port pick

README.md

@@ -44,6 +44,43 @@ worker.onmessage = function (ev) {
 worker.postMessage("Hello World!");
 ```
 
+# Debugging
+To be able to debug a child process, it must have a differnt debug port than the parent. 
+Tiny worker does this by adding a random port within a range to the parents debug port.
+The default Range is `[1, 300]`, it can be changed with the `setRange(min, max)` method.
+To disable any automatic port redirection set `options.noDebugRedirection = true`.
+
+### automatic redirection
+```javascript
+//parent is started with '--debug=1234'
+var Worker = require("tiny-worker");
+Worker.setRange(2, 20);
+
+var worker = new Worker(function () {
+	postMessage(process.debugPort); 
+});
+
+worker.onmessage = function (ev) {
+	console.log(ev.data); //prints any number between 1236 and 1254
+	worker.terminate();
+}
+```
+
+### manual redirection
+```javascript
+//parent is started with '--debug=1234'
+var Worker = require("tiny-worker");
+
+var worker = new Worker(function () {
+	postMessage(process.debugPort); 
+}, [], {noDebugRedirection: true, execArgv: ["--debug=1235"]});
+
+worker.onmessage = function (ev) {
+	console.log(ev.data); //prints 1235
+	worker.terminate();
+}
+```
+
 ## Properties
 #### onmessage
 Message handler, accepts an `Event`
@@ -61,6 +98,10 @@ Broadcasts a message to the `Worker`
 #### terminate()
 Terminates the `Worker`
 
+#### static setRange(min, max)
+Sets range for debug ports, only affects current process.
+Returns true if successful.
+
 ## FAQ
 1. I have an orphaned child process that lives on past the parent process' lifespan
   * Most likely a `SIGTERM` or `SIGINT` is not reaching the child process

lib/index.js

@@ -9,13 +9,13 @@ var path = require("path"),
     worker = path.join(__dirname, "worker.js"),
     events = /^(error|message)$/,
     defaultPorts = { inspect: 9229, debug: 5858 };
-var forkedChilds = 0;
+var range = { min: 1, max: 300 };
 
 var Worker = function () {
 	function Worker(arg) {
 		var _this = this;
 
-		var args = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : undefined;
+		var args = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : [];
 		var options = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : { cwd: process.cwd() };
 
 		_classCallCheck(this, Worker);
@@ -59,8 +59,7 @@ var Worker = function () {
 				if (match[2]) {
 					port = parseInt(match[2]);
 				}
-				debugVars[portIndex] = "--" + match[1] + "=" + (port + 1 + forkedChilds); //new parameter
-				forkedChilds++;
+				debugVars[portIndex] = "--" + match[1] + "=" + (port + range.min + Math.floor(Math.random() * (range.max - range.min))); //new parameter
 
 				if (debugIndex >= 0 && debugIndex !== portIndex) {
 					//remove "-brk" from debug if there
@@ -119,6 +118,17 @@ var Worker = function () {
 		value: function terminate() {
 			this.child.kill("SIGINT");
 		}
+	}], [{
+		key: "setRange",
+		value: function setRange(min, max) {
+			if (min >= max) {
+				return false;
+			}
+			range.min = min;
+			range.max = max;
+
+			return true;
+		}
 	}]);
 
 	return Worker;

src/index.js

@@ -3,10 +3,10 @@ const path = require("path"),
 	worker = path.join(__dirname, "worker.js"),
 	events = /^(error|message)$/,
 	defaultPorts = {inspect: 9229, debug: 5858};
-let forkedChilds = 0;
+let range = {min: 1, max: 300};
 
 class Worker {
-	constructor (arg, args = undefined, options = {cwd: process.cwd()}) {
+	constructor (arg, args = [], options = {cwd: process.cwd()}) {
 		let isfn = typeof arg === "function",
 			input = isfn ? arg.toString() : arg;
 
@@ -40,8 +40,7 @@ class Worker {
 				if (match[2]) {
 					port = parseInt(match[2]);
 				}
-				debugVars[portIndex] = "--" + match[1] + "=" + (port + 1 + forkedChilds); //new parameter
-				forkedChilds++;
+				debugVars[portIndex] = "--" + match[1] + "=" + (port + range.min + Math.floor(Math.random() * (range.max - range.min))); //new parameter
 
 				if (debugIndex >= 0 && debugIndex !== portIndex) { //remove "-brk" from debug if there
 					match = (/^(--debug)(?:-brk)?(.*)/).exec(debugVars[debugIndex]);
@@ -83,6 +82,16 @@ class Worker {
 		this.child.send({input: input, isfn: isfn, cwd: options.cwd});
 	}
 
+	static setRange (min, max) {
+		if (min >= max) {
+			return false;
+		}
+		range.min = min;
+		range.max = max;
+
+		return true;
+	}
+
 	addEventListener (event, fn) {
 		if (events.test(event)) {
 			this["on" + event] = fn;