diff --git a/src/kernel/Communicator.cc b/src/kernel/Communicator.cc
index 674dd6fd..54fe7020 100644
--- a/src/kernel/Communicator.cc
+++ b/src/kernel/Communicator.cc
@@ -1141,8 +1141,12 @@ void Communicator::handler_thread_routine(void *context)
 	Communicator *comm = (Communicator *)context;
 	struct poller_result *res;
 
-	while ((res = (struct poller_result *)msgqueue_get(comm->queue)) != NULL)
+	while (1)
 	{
+		res = (struct poller_result *)msgqueue_get(comm->msgqueue);
+		if (!res)
+			break;
+
 		switch (res->data.operation)
 		{
 		case PD_OP_READ:
@@ -1174,7 +1178,8 @@ void Communicator::handler_thread_routine(void *context)
 	}
 }
 
-int Communicator::append(const void *buf, size_t *size, poller_message_t *msg)
+int Communicator::append_request(const void *buf, size_t *size,
+								 poller_message_t *msg)
 {
 	CommMessageIn *in = (CommMessageIn *)msg;
 	struct CommConnEntry *entry = in->entry;
@@ -1186,17 +1191,37 @@ int Communicator::append(const void *buf, size_t *size, poller_message_t *msg)
 	if (ret > 0)
 	{
 		entry->state = CONN_STATE_SUCCESS;
-		if (entry->service)
-			timeout = -1;
-		else
+		timeout = -1;
+	}
+	else if (ret == 0 && session->timeout != 0)
+		timeout = Communicator::next_timeout(session);
+	else
+		return ret;
+
+	/* This set_timeout() never fails, which is very important. */
+	mpoller_set_timeout(entry->sockfd, timeout, entry->mpoller);
+	return ret;
+}
+
+int Communicator::append_reply(const void *buf, size_t *size,
+							   poller_message_t *msg)
+{
+	CommMessageIn *in = (CommMessageIn *)msg;
+	struct CommConnEntry *entry = in->entry;
+	CommSession *session = entry->session;
+	int timeout;
+	int ret;
+
+	ret = in->append(buf, size);
+	if (ret > 0)
+	{
+		entry->state = CONN_STATE_SUCCESS;
+		timeout = session->keep_alive_timeout();
+		session->timeout = timeout; /* Reuse session's timeout field. */
+		if (timeout == 0)
 		{
-			timeout = session->keep_alive_timeout();
-			session->timeout = timeout; /* Reuse session's timeout field. */
-			if (timeout == 0)
-			{
-				mpoller_del(entry->sockfd, entry->mpoller);
-				return ret;
-			}
+			mpoller_del(entry->sockfd, entry->mpoller);
+			return ret;
 		}
 	}
 	else if (ret == 0 && session->timeout != 0)
@@ -1256,32 +1281,50 @@ int Communicator::create_service_session(struct CommConnEntry *entry)
 	return -1;
 }
 
-poller_message_t *Communicator::create_message(void *context)
+poller_message_t *Communicator::create_request(struct CommConnEntry *entry)
 {
-	struct CommConnEntry *entry = (struct CommConnEntry *)context;
 	CommSession *session;
 
 	if (entry->state == CONN_STATE_IDLE)
 	{
-		pthread_mutex_t *mutex;
-
-		if (entry->service)
-			mutex = &entry->target->mutex;
-		else
-			mutex = &entry->mutex;
-
-		pthread_mutex_lock(mutex);
+		pthread_mutex_lock(&entry->target->mutex);
 		/* do nothing */
-		pthread_mutex_unlock(mutex);
+		pthread_mutex_unlock(&entry->target->mutex);
 	}
 
-	if (entry->state == CONN_STATE_CONNECTED ||
-		entry->state == CONN_STATE_KEEPALIVE)
+	if (entry->state != CONN_STATE_KEEPALIVE &&
+		entry->state != CONN_STATE_CONNECTED)
 	{
-		if (Communicator::create_service_session(entry) < 0)
-			return NULL;
+		errno = EBADMSG;
+		return NULL;
 	}
-	else if (entry->state != CONN_STATE_RECEIVING)
+
+	if (Communicator::create_service_session(entry) < 0)
+		return NULL;
+
+	session = entry->session;
+	session->in = session->message_in();
+	if (session->in)
+	{
+		session->in->poller_message_t::append = Communicator::append_request;
+		session->in->entry = entry;
+	}
+
+	return session->in;
+}
+
+poller_message_t *Communicator::create_reply(struct CommConnEntry *entry)
+{
+	CommSession *session;
+
+	if (entry->state == CONN_STATE_IDLE)
+	{
+		pthread_mutex_lock(&entry->mutex);
+		/* do nothing */
+		pthread_mutex_unlock(&entry->mutex);
+	}
+
+	if (entry->state != CONN_STATE_RECEIVING)
 	{
 		errno = EBADMSG;
 		return NULL;
@@ -1291,13 +1334,23 @@ poller_message_t *Communicator::create_message(void *context)
 	session->in = session->message_in();
 	if (session->in)
 	{
-		session->in->poller_message_t::append = Communicator::append;
+		session->in->poller_message_t::append = Communicator::append_reply;
 		session->in->entry = entry;
 	}
 
 	return session->in;
 }
 
+poller_message_t *Communicator::create_message(void *context)
+{
+	struct CommConnEntry *entry = (struct CommConnEntry *)context;
+
+	if (entry->service)
+		return Communicator::create_request(entry);
+	else
+		return Communicator::create_reply(entry);
+}
+
 int Communicator::partial_written(size_t n, void *context)
 {
 	struct CommConnEntry *entry = (struct CommConnEntry *)context;
@@ -1311,8 +1364,8 @@ int Communicator::partial_written(size_t n, void *context)
 
 void Communicator::callback(struct poller_result *res, void *context)
 {
-	Communicator *comm = (Communicator *)context;
-	msgqueue_put(res, comm->queue);
+	msgqueue_t *msgqueue = (msgqueue_t *)context;
+	msgqueue_put(res, msgqueue);
 }
 
 void *Communicator::accept(const struct sockaddr *addr, socklen_t addrlen,
@@ -1359,7 +1412,7 @@ int Communicator::create_handler_threads(size_t handler_threads)
 		if (i == handler_threads)
 			return 0;
 
-		msgqueue_set_nonblock(this->queue);
+		msgqueue_set_nonblock(this->msgqueue);
 		thrdpool_destroy(NULL, this->thrdpool);
 	}
 
@@ -1373,15 +1426,15 @@ int Communicator::create_poller(size_t poller_threads)
 		.create_message		=	Communicator::create_message,
 		.partial_written	=	Communicator::partial_written,
 		.callback			=	Communicator::callback,
-		.context			=	this
 	};
 
 	if ((ssize_t)params.max_open_files < 0)
 		return -1;
 
-	this->queue = msgqueue_create(4096, sizeof (struct poller_result));
-	if (this->queue)
+	this->msgqueue = msgqueue_create(4096, sizeof (struct poller_result));
+	if (this->msgqueue)
 	{
+		params.context = this->msgqueue;
 		this->mpoller = mpoller_create(&params, poller_threads);
 		if (this->mpoller)
 		{
@@ -1391,7 +1444,7 @@ int Communicator::create_poller(size_t poller_threads)
 			mpoller_destroy(this->mpoller);
 		}
 
-		msgqueue_destroy(this->queue);
+		msgqueue_destroy(this->msgqueue);
 	}
 
 	return -1;
@@ -1415,7 +1468,7 @@ int Communicator::init(size_t poller_threads, size_t handler_threads)
 
 		mpoller_stop(this->mpoller);
 		mpoller_destroy(this->mpoller);
-		msgqueue_destroy(this->queue);
+		msgqueue_destroy(this->msgqueue);
 	}
 
 	return -1;
@@ -1425,10 +1478,10 @@ void Communicator::deinit()
 {
 	this->stop_flag = 1;
 	mpoller_stop(this->mpoller);
-	msgqueue_set_nonblock(this->queue);
+	msgqueue_set_nonblock(this->msgqueue);
 	thrdpool_destroy(NULL, this->thrdpool);
 	mpoller_destroy(this->mpoller);
-	msgqueue_destroy(this->queue);
+	msgqueue_destroy(this->msgqueue);
 }
 
 int Communicator::nonblock_connect(CommTarget *target)
diff --git a/src/kernel/Communicator.h b/src/kernel/Communicator.h
index e2e129d6..92bf4094 100644
--- a/src/kernel/Communicator.h
+++ b/src/kernel/Communicator.h
@@ -280,7 +280,7 @@ public:
 
 private:
 	struct __mpoller *mpoller;
-	struct __msgqueue *queue;
+	struct __msgqueue *msgqueue;
 	struct __thrdpool *thrdpool;
 	int stop_flag;
 
@@ -341,10 +341,16 @@ private:
 	static int first_timeout_send(CommSession *session);
 	static int first_timeout_recv(CommSession *session);
 
-	static int append(const void *buf, size_t *size, poller_message_t *msg);
+	static int append_request(const void *buf, size_t *size,
+							  poller_message_t *msg);
+	static int append_reply(const void *buf, size_t *size,
+							poller_message_t *msg);
 
 	static int create_service_session(struct CommConnEntry *entry);
 
+	static poller_message_t *create_request(struct CommConnEntry *entry);
+	static poller_message_t *create_reply(struct CommConnEntry *entry);
+
 	static poller_message_t *create_message(void *context);
 
 	static int partial_written(size_t n, void *context);
diff --git a/src/util/json_parser.c b/src/util/json_parser.c
index 6f39ed85..7014d90f 100644
--- a/src/util/json_parser.c
+++ b/src/util/json_parser.c
@@ -43,7 +43,6 @@ struct __json_array
 
 struct __json_value
 {
-	int type;
 	union
 	{
 		char *string;
@@ -51,6 +50,7 @@ struct __json_value
 		json_object_t object;
 		json_array_t array;
 	} value;
+	int type;
 };
 
 struct __json_member