Fix getFreePort() (#627)

Signed-off-by: Lauri Nevala <lauri.nevala@gmail.com>

src/main/port.ts

@@ -6,7 +6,8 @@ import logger from "./logger"
 export async function getFreePort(): Promise<number> {
   logger.debug("Lookup new free port..");
   return new Promise((resolve, reject) => {
-    const server = net.createServer().unref().listen({ port: 0 });
+    const server = net.createServer()
+    server.unref()
     server.on("listening", () => {
       const port = (server.address() as AddressInfo).port
       server.close(() => resolve(port));
@@ -16,5 +17,6 @@ export async function getFreePort(): Promise<number> {
       logger.error(`Can't resolve new port: "${error}"`);
       reject(error);
     });
+    server.listen({ host: "127.0.0.1", port: 0 })
   })
 }