--- a/src/goodjava/lucene/backup/BackupIndexWriter.java	Mon Oct 20 14:45:27 2025 -0600
+++ b/src/goodjava/lucene/backup/BackupIndexWriter.java	Mon Oct 20 17:25:47 2025 -0600
@@ -231,4 +231,21 @@
 		return new BackupIndexWriter(indexWriter,logDir,logTime,domain,name);
 	}
 
+	// returns failed domain or null
+	public static String ping() throws IOException {
+		if( backupDomains == null ) {
+			logger.error("backupDomains not set");
+			return null;
+		}
+		for( String backupDomain : backupDomains ) {
+			try {
+				Socket socket = BackupServer.clientSocket(backupDomain);
+				socket.close();
+			} catch(ConnectException e) {
+				return backupDomain;
+			}
+		}
+		return null;
+	}
+
 }