diff --git a/src/main/java/org/bdware/server/CMHttpServer.java b/src/main/java/org/bdware/server/CMHttpServer.java
index cd814d9..965bbd5 100644
--- a/src/main/java/org/bdware/server/CMHttpServer.java
+++ b/src/main/java/org/bdware/server/CMHttpServer.java
@@ -17,6 +17,8 @@ import io.netty.handler.ssl.OptionalSslHandler;
 import io.netty.handler.ssl.SslContext;
 import io.netty.handler.ssl.SslContextBuilder;
 import io.netty.handler.stream.ChunkedWriteHandler;
+import io.netty.handler.timeout.IdleStateEvent;
+import io.netty.handler.timeout.IdleStateHandler;
 import io.netty.util.internal.StringUtil;
 import io.prometheus.client.exporter.HTTPServer;
 import org.apache.commons.io.FileUtils;
@@ -95,12 +97,12 @@ public class CMHttpServer {
         if (!cmdConf.withBdledgerClient.isEmpty()) {
             ContractManager.scheduledThreadPool.schedule(() -> {
                 File ledgerClient = new File(cmdConf.withBdledgerClient);
-                LOGGER.debug("canRead=" + ledgerClient.canRead() + " path="
-                        + ledgerClient.getAbsolutePath());
+                LOGGER.debug("canRead={} path={}", ledgerClient.canRead(),
+                        ledgerClient.getAbsolutePath());
                 try {
                     Runtime.getRuntime().exec(ledgerClient.getAbsolutePath());
                 } catch (IOException e) {
-                    LOGGER.warn("start bdledger client failed: " + e.getMessage());
+                    LOGGER.warn("start bdledger client failed: {}", e.getMessage());
                 }
             }, 1, TimeUnit.SECONDS);
         }
@@ -118,10 +120,10 @@ public class CMHttpServer {
                                             .stream().filter(x -> null != x && !x.contains("RC4"))
                                             .toArray(String[]::new))
                             .build();
-                    LOGGER.info("openssl isAvailable:" + OpenSsl.isAvailable());
+                    LOGGER.info("openssl isAvailable:{}", OpenSsl.isAvailable());
                 }
             } catch (Exception e) {
-                LOGGER.warn("Enabling SSL failed: " + e.getMessage());
+                LOGGER.warn("Enabling SSL failed: {}", e.getMessage());
                 LOGGER.debug(ExceptionUtil.exceptionToString(e));
             }
         }
@@ -131,7 +133,7 @@ public class CMHttpServer {
         FileWriter fw = new FileWriter("CMI");
         fw.write(ContractClient.cmi);
         fw.close();
-        LOGGER.info("write CMI=" + ContractClient.cmi + " to ./CMI");
+        LOGGER.info("write CMI={} to ./CMI", ContractClient.cmi);
         FileActions.setTextFileSuffixes(cmdConf.textFileSuffixes);
 
         // plugins
@@ -149,7 +151,7 @@ public class CMHttpServer {
                         break;
                     }
                     Configurator.setLevel(clz, Level.DEBUG);
-                    LOGGER.warn("set debug: " + clz);
+                    LOGGER.warn("set debug: {}", clz);
                 }
             } catch (Exception e) {
                 LOGGER.warn(e.getMessage());
@@ -190,7 +192,7 @@ public class CMHttpServer {
 
     private static void addDirToPath(String s) {
         try {
-            LOGGER.info("add to path: " + s);
+            LOGGER.info("add to path: {}", s);
             // Field field = ClassLoader.class.getDeclaredField("sys_paths");
             Field field = ClassLoader.class.getDeclaredField("usr_paths");
             field.setAccessible(true);
@@ -262,8 +264,8 @@ public class CMHttpServer {
     }
 
     public static void start(int port) throws IOException {
-        LOGGER.info("start server at:" + port);
-        LOGGER.debug("dir:" + new File("./").getAbsolutePath());
+        LOGGER.info("start server at:{}", port);
+        LOGGER.debug("dir:{}", new File("./").getAbsolutePath());
         new CMHttpServer(port).start();
         // never reach here!!
     }
@@ -285,7 +287,7 @@ public class CMHttpServer {
             for (int i = 0; i < pluginJar.length; i++) {
                 try {
                     urls[i] = pluginJar[i].toURI().toURL();
-                    LOGGER.info("add plugin:" + pluginJar[i].getName());
+                    LOGGER.info("add plugin:{}", pluginJar[i].getName());
                 } catch (MalformedURLException e) {
                     e.printStackTrace();
                 }
@@ -319,10 +321,24 @@ public class CMHttpServer {
                                     .addLast(new WebSocketServerProtocolHandler(PATH, null, true))
                                     .addLast(new ChunkedWriteHandler()).addLast(serverHandler)
                                     .addLast(new ContractManagerFrameHandler());
+                            arg0.pipeline().addLast(new IdleStateHandler(120, 0, 0))
+                                    .addLast(new ChannelDuplexHandler() {
+                                        @Override
+                                        public void userEventTriggered(ChannelHandlerContext ctx,
+                                                Object evt) {
+                                            if (evt instanceof IdleStateEvent) {
+                                                IdleStateEvent stateEvent = (IdleStateEvent) evt;
+                                                LOGGER.warn(
+                                                        "Detected channel idle event: {}; auto close!",
+                                                        stateEvent.state());
+                                                ctx.channel().close();
+                                            }
+                                        }
+                                    });
                         }
                     });
             final Channel ch = b1.bind(port).sync().channel();
-            LOGGER.debug("[CMHttpServer] listen master port at:" + port);
+            LOGGER.debug("[CMHttpServer] listen master port at:{}", port);
             new HTTPServer(port + 3);
             NetworkManager.instance.initTCP(port + 1, workerGroup);
 
@@ -340,7 +356,7 @@ public class CMHttpServer {
     }
 
     private void loadStartContractConfiguration() {
-        if (cmdConf.startContract != null && cmdConf.startContract.size() > 0) {
+        if (cmdConf.startContract != null && !cmdConf.startContract.isEmpty()) {
             ContractManager.scheduledThreadPool.schedule(() -> {
                 for (JsonElement je : cmdConf.startContract) {
                     try {