find free ports: make it work, add timeout and tests

src/vs/base/node/ports.ts

@@ -11,23 +11,60 @@ import net = require('net');
  * Given a start point and a max number of retries, will find a port that
  * is openable. Will return 0 in case no free port can be found.
  */
-export function findFreePort(startPort: number, giveUpAfter:number, clb: (port: number) => void): void {
+export function findFreePort(startPort: number, giveUpAfter: number, timeout: number, clb: (port: number) => void): void {
+	let done = false;
+
+	const timeoutHandle = setTimeout(() =>  {
+		if (!done) {
+			done = true;
+
+			return clb(0);
+		}
+	}, timeout);
+
+	doFindFreePort(startPort, giveUpAfter, (port) => {
+		if (!done) {
+			done = true;
+			window.clearInterval(timeoutHandle);
+
+			return clb(port);
+		}
+	});
+}
+
+function doFindFreePort(startPort: number, giveUpAfter: number, clb: (port: number) => void): void {
 	if (giveUpAfter === 0) {
 		return clb(0);
 	}
 
-	let tryPort = startPort;
+	const client = new net.Socket();
 
-	let server = net.createServer();
-	server.listen(tryPort, (err) => {
-		server.once('close', () => {
-			return clb(tryPort);
-		});
+	// If we can connect to the port it means the port is already taken so we continue searching
+	client.once('connect', () => {
+		dispose(client);
 
-		server.close();
+		return doFindFreePort(startPort + 1, giveUpAfter - 1, clb);
 	});
 
-	server.on('error', (err) => {
-		findFreePort(startPort + 1, giveUpAfter - 1, clb);
+	client.once('error', (err) => {
+		dispose(client);
+
+		// If we receive any non ECONNREFUSED error, it means the port is used but we cannot connect
+		if (err.code !== 'ECONNREFUSED') {
+			return doFindFreePort(startPort + 1, giveUpAfter - 1, clb);
+		}
+
+		// Otherwise it means the port is free to use!
+		return clb(startPort);
 	});
+
+	client.connect(startPort);
+}
+
+function dispose(socket: net.Socket): void {
+	socket.removeAllListeners('connect');
+	socket.removeAllListeners('error');
+	socket.end();
+	socket.destroy();
+	socket.unref();
 }
\ No newline at end of file

src/vs/base/test/node/port.test.ts

@@ -10,18 +10,18 @@ import * as net from 'net';
 import ports = require('vs/base/node/ports');
 
 suite('Ports', () => {
-	test('Finds a free port', function (done: () => void) {
+	test('Finds a free port (no timeout)', function (done: () => void) {
 
 		// get an initial freeport >= 7000
-		ports.findFreePort(7000, 100, (initialPort) => {
+		ports.findFreePort(7000, 100, 300000, (initialPort) => {
 			assert.ok(initialPort >= 7000);
 
 			// create a server to block this port
 			const server = net.createServer();
-			server.listen(initialPort, null, null, () => {
+			server.listen(initialPort, null, null, () =>  {
 
 				// once listening, find another free port and assert that the port is different from the opened one
-				ports.findFreePort(7000, 50, (freePort) => {
+				ports.findFreePort(7000, 50, 300000, (freePort) => {
 					assert.ok(freePort >= 7000 && freePort !== initialPort);
 					server.close();
 
@@ -30,4 +30,25 @@ suite('Ports', () => {
 			});
 		});
 	});
+
+	test('Finds a free port (with timeout)', function (done: () => void) {
+
+		// get an initial freeport >= 7000
+		ports.findFreePort(7000, 100, 300000, (initialPort) => {
+			assert.ok(initialPort >= 7000);
+
+			// create a server to block this port
+			const server = net.createServer();
+			server.listen(initialPort, null, null, () =>  {
+
+				// once listening, find another free port and assert that the port is different from the opened one
+				ports.findFreePort(7000, 50, 0, (freePort) => {
+					assert.equal(freePort, 0);
+					server.close();
+
+					done();
+				});
+			});
+		});
+	});
 });
\ No newline at end of file

src/vs/workbench/services/thread/electron-browser/threadService.ts

@@ -275,7 +275,7 @@ class ExtensionHostProcessManager {
 
 		// Check for a free debugging port
 		if (typeof config.env.debugExtensionHostPort === 'number') {
-			return findFreePort(config.env.debugExtensionHostPort, 10 /* try 10 ports */, (port) => {
+			return findFreePort(config.env.debugExtensionHostPort, 10 /* try 10 ports */, 5000 /* try up to 5 seconds */, (port) => {
 				if (!port) {
 					console.warn('%c[Extension Host] %cCould not find a free port for debugging', 'color: blue', 'color: black');