@ngocdaothanh would you mind submitting a PR ?
 Sure! I wanted to confirm if my guess was right.
 I've sent pull requests for branch 4.0, 4.1, and master.

%s WebSocket version %s server handshake
1.

In https://github.com/netty/netty/blob/master/codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocketServerHandshaker.java

``` java
logger.debug("%s WebSocket version %s server handshake", channel, version());
```

I guess it should be:

``` java
logger.debug("{} WebSocket version {} server handshake", channel, version());
```

2.

In https://github.com/netty/netty/blob/master/codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocketServerHandshaker07.java

``` java
logger.debug("WebSocket version 07 server handshake key: {}, response: %s.", key, accept);
```

I guess it should be:

``` java
logger.debug("WebSocket version 07 server handshake key: {}, response: {}.", key, accept);
```

codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocketServerHandshaker.java codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocketServerHandshaker07.java
codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocketServerHandshaker.java codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocketServerHandshaker07.java
diff --git a/codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocketServerHandshaker.java b/codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocketServerHandshaker.java
index f94b4f79f3e..c2ca118d351 100644
--- a/codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocketServerHandshaker.java
+++ b/codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocketServerHandshaker.java
@@ -156,7 +156,7 @@ public final ChannelFuture handshake(Channel channel, FullHttpRequest req,
                                             HttpHeaders responseHeaders, final ChannelPromise promise) {
 
         if (logger.isDebugEnabled()) {
-            logger.debug("%s WebSocket version %s server handshake", channel, version());
+            logger.debug("{} WebSocket version {} server handshake", channel, version());
         }
         FullHttpResponse response = newHandshakeResponse(req, responseHeaders);
         ChannelPipeline p = channel.pipeline();
diff --git a/codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocketServerHandshaker07.java b/codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocketServerHandshaker07.java
index 329f823bd4e..52f461eaccc 100644
--- a/codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocketServerHandshaker07.java
+++ b/codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocketServerHandshaker07.java
@@ -111,7 +111,7 @@ protected FullHttpResponse newHandshakeResponse(FullHttpRequest req, HttpHeaders
         String accept = WebSocketUtil.base64(sha1);
 
         if (logger.isDebugEnabled()) {
-            logger.debug("WebSocket version 07 server handshake key: {}, response: %s.", key, accept);
+            logger.debug("WebSocket version 07 server handshake key: {}, response: {}.", key, accept);
         }
 
         res.headers().add(Names.UPGRADE, WEBSOCKET.toLowerCase());
