chore: log watchdog client connection error (#13475)

It may happen that the watchdog client started by webpack
fails to connect for some reason, for example when server
socket is bound to ipv4 only and client resolve localhost
with its ipv6 address (e.g. with node 17).
This change adds the detail of the connection error to the
log message, so that debugging this kind of situation may
be simpler.

flow-server/src/main/resources/vite.generated.ts

@@ -292,8 +292,8 @@ function updateTheme(contextPath: string) {
 function runWatchDog(watchDogPort) {
   const client = net.Socket();
   client.setEncoding('utf8');
-  client.on('error', function () {
-    console.log('Watchdog connection error. Terminating vite process...');
+  client.on('error', function (err) {
+    console.log('Watchdog connection error. Terminating vite process...', err);
     client.destroy();
     process.exit(0);
   });

flow-server/src/main/resources/webpack.generated.js

@@ -96,8 +96,8 @@ if (watchDogPort) {
   const runWatchDog = () => {
     const client = new require('net').Socket();
     client.setEncoding('utf8');
-    client.on('error', function () {
-      console.log('Watchdog connection error. Terminating webpack process...');
+    client.on('error', function (err) {
+      console.log('Watchdog connection error. Terminating webpack process...', err);
       client.destroy();
       process.exit(0);
     });