Reduce checkpoint exceptions by TCP retry and silent jar updates

SpigotCore_Main/src/de/steamwar/core/CheckpointUtils.java

@@ -69,7 +69,16 @@ public class CheckpointUtils {
         try {
             freezeInternal(path);
         } catch (Exception e) {
+            String message = e.getMessage() != null ? e.getMessage() : "";
+            if(message.contains("Connected TCP socket")) {
+                Core.getInstance().getLogger().log(Level.INFO, "Connected TCP socket, waiting for checkpointing");
+                Bukkit.getScheduler().runTaskLater(Core.getInstance(), CheckpointUtils::freeze, 1);
+                return;
+            }
+
             Bukkit.shutdown();
+
+            if(message.contains("Can't dump ghost file")) // File/Jar has been updated
                 throw new SecurityException(e);
         } finally {
             // Delete checkpoint
@@ -109,8 +118,6 @@ public class CheckpointUtils {
         try {
             criu.checkpointJVM();
         } catch (JVMCRIUException e) {
-            Bukkit.shutdown();
-
             Path logfile = path.resolve("criu.log");
             if(logfile.toFile().exists())
                 throw new IllegalStateException("Could not create checkpoint, criu log:\n" + new String(Files.readAllBytes(logfile)), e);