Lens app source code (#119)

Signed-off-by: Jari Kolehmainen <jari.kolehmainen@gmail.com>

src/main/port.ts

@@ -0,0 +1,27 @@
+import logger from "./logger"
+import { createServer } from "net"
+
+// Adapted from https://gist.github.com/mikeal/1840641#gistcomment-2896667
+function checkPort(port: number) {
+  const server = createServer()
+  server.unref()
+  return new Promise((resolve, reject) =>
+    server
+      .on('error', error => reject(error))
+      .on('listening', () => server.close(() => resolve(port)))
+      .listen({host: "127.0.0.1", port: port}))
+}
+
+export async function getFreePort(firstPort: number, lastPort: number): Promise<number> {
+  let port = firstPort
+
+  while(true) {
+    try {
+      logger.debug("Checking port " + port + " availability ...")
+      await checkPort(port)
+      return(port)
+    } catch(error) {
+      if(++port > lastPort) throw("Could not find a free port")
+    }
+  }
+}