diff --git a/CMakeLists.txt b/CMakeLists.txt
index afde4ac..9763fd8 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -19,6 +19,7 @@ if(WEBCC_BUILD_UNITTEST)
     enable_testing()
 endif()
 
+# Automatically detect _WIN32_WINNT for Asio.
 # See: https://stackoverflow.com/a/40217291
 if(WIN32)
 	macro(get_WIN32_WINNT version)
diff --git a/example/soap_calc_client/calc_client.cc b/example/soap_calc_client/calc_client.cc
index 293b0bf..6b358fb 100644
--- a/example/soap_calc_client/calc_client.cc
+++ b/example/soap_calc_client/calc_client.cc
@@ -1,6 +1,7 @@
 #include "calc_client.h"
 #include <iostream>
 #include "boost/lexical_cast.hpp"
+#include "webcc/logger.h"
 
 // Set to 0 to test our own calculator server created with webcc.
 #define ACCESS_PARASOFT 0
@@ -71,8 +72,9 @@ bool CalcClient::Calc(const std::string& operation,
 
   // Error handling if any.
   if (error != webcc::kNoError) {
-    std::cerr << "Error: " << error;
-    std::cerr << ", " << webcc::GetErrorMessage(error) << std::endl;
+    LOG_ERRO("Operation '%s' failed: %s",
+             operation.c_str(),
+             webcc::GetErrorMessage(error));
     return false;
   }
 
diff --git a/example/soap_calc_client/main.cc b/example/soap_calc_client/main.cc
index 2903cde..799df26 100644
--- a/example/soap_calc_client/main.cc
+++ b/example/soap_calc_client/main.cc
@@ -1,7 +1,10 @@
 #include <iostream>
+#include "webcc/logger.h"
 #include "calc_client.h"
 
 int main() {
+  LOG_INIT(webcc::INFO, 0);
+
   CalcClient calc;
 
   double x = 1.0;
diff --git a/example/soap_calc_server/main.cc b/example/soap_calc_server/main.cc
index be1bd79..65f5846 100644
--- a/example/soap_calc_server/main.cc
+++ b/example/soap_calc_server/main.cc
@@ -15,7 +15,7 @@ int main(int argc, char* argv[]) {
     return 1;
   }
 
-  LOG_INIT(webcc::VERB, 0);
+  LOG_INIT(webcc::INFO, 0);
 
   unsigned short port = std::atoi(argv[1]);
 
diff --git a/src/webcc/common.cc b/src/webcc/common.cc
index 522a088..dfd219c 100644
--- a/src/webcc/common.cc
+++ b/src/webcc/common.cc
@@ -63,7 +63,7 @@ const char* GetErrorMessage(Error error) {
 
 ////////////////////////////////////////////////////////////////////////////////
 
-const Namespace kSoapEnvNamespace{
+const SoapNamespace kSoapEnvNamespace{
   "soap",
   "http://schemas.xmlsoap.org/soap/envelope/"
 };
diff --git a/src/webcc/common.h b/src/webcc/common.h
index c1ee327..c5086b2 100644
--- a/src/webcc/common.h
+++ b/src/webcc/common.h
@@ -87,8 +87,7 @@ const char* GetErrorMessage(Error error);
 
 // XML namespace name/url pair.
 // E.g., { "soap", "http://schemas.xmlsoap.org/soap/envelope/" }
-// TODO: Rename (add soap prefix)
-class Namespace {
+class SoapNamespace {
 public:
   std::string name;
   std::string url;
@@ -99,12 +98,11 @@ public:
 };
 
 // CSoap's default namespace for SOAP Envelope.
-extern const Namespace kSoapEnvNamespace;
+extern const SoapNamespace kSoapEnvNamespace;
 
 ////////////////////////////////////////////////////////////////////////////////
 
-// Parameter in the SOAP request envelope.
-// TODO: Rename (add soap prefix)
+// Key-value parameter.
 class Parameter {
 public:
   Parameter() = default;
diff --git a/src/webcc/http_client.h b/src/webcc/http_client.h
index afb2152..22be370 100644
--- a/src/webcc/http_client.h
+++ b/src/webcc/http_client.h
@@ -19,7 +19,6 @@ class HttpResponse;
 class HttpClient {
 public:
   HttpClient();
-
   ~HttpClient() = default;
 
   HttpClient(const HttpClient&) = delete;
diff --git a/src/webcc/http_request_handler.cc b/src/webcc/http_request_handler.cc
index b07c78c..b0fbce5 100644
--- a/src/webcc/http_request_handler.cc
+++ b/src/webcc/http_request_handler.cc
@@ -22,12 +22,12 @@ void HttpRequestHandler::Start(std::size_t count) {
 }
 
 void HttpRequestHandler::Stop() {
-  LOG_VERB("Stopping workers...");
+  LOG_INFO("Stopping workers...");
 
   // Close pending sessions.
   for (HttpSessionPtr conn = queue_.Pop(); conn; conn = queue_.Pop()) {
-    LOG_VERB("Closing pending session...");
-    conn->Stop();
+    LOG_INFO("Closing pending session...");
+    conn->Close();
   }
 
   // Enqueue a null session to trigger the first worker to stop.
@@ -35,17 +35,17 @@ void HttpRequestHandler::Stop() {
 
   workers_.join_all();
 
-  LOG_VERB("All workers have been stopped.");
+  LOG_INFO("All workers have been stopped.");
 }
 
 void HttpRequestHandler::WorkerRoutine() {
-  LOG_VERB("Worker is running.");
+  LOG_INFO("Worker is running.");
 
   for (;;) {
     HttpSessionPtr session = queue_.PopOrWait();
 
     if (!session) {
-      LOG_VERB("Worker is going to stop.");
+      LOG_INFO("Worker is going to stop.");
 
       // For stopping next worker.
       queue_.Push(HttpSessionPtr());
diff --git a/src/webcc/http_server.cc b/src/webcc/http_server.cc
index 7d29324..b71281f 100644
--- a/src/webcc/http_server.cc
+++ b/src/webcc/http_server.cc
@@ -25,7 +25,7 @@ HttpServer::HttpServer(unsigned short port, std::size_t workers)
   signals_.add(SIGQUIT);
 #endif
 
-  DoAwaitStop();
+  AsyncAwaitStop();
 
   // NOTE:
   // "reuse_addr=true" means option SO_REUSEADDR will be set.
@@ -37,16 +37,13 @@ HttpServer::HttpServer(unsigned short port, std::size_t workers)
                                     tcp::endpoint(tcp::v4(), port),
                                     true));  // reuse_addr
 
-  DoAccept();
-}
-
-HttpServer::~HttpServer() {
+  AsyncAccept();
 }
 
 void HttpServer::Run() {
   assert(GetRequestHandler() != NULL);
 
-  LOG_VERB("Server is going to run...");
+  LOG_INFO("Server is going to run...");
 
   // Start worker threads.
   GetRequestHandler()->Start(workers_);
@@ -58,7 +55,7 @@ void HttpServer::Run() {
   io_context_.run();
 }
 
-void HttpServer::DoAccept() {
+void HttpServer::AsyncAccept() {
   acceptor_->async_accept(
       [this](boost::system::error_code ec, tcp::socket socket) {
         // Check whether the server was stopped by a signal before this
@@ -68,17 +65,19 @@ void HttpServer::DoAccept() {
         }
 
         if (!ec) {
+          LOG_INFO("Accepted a connection.");
+
           HttpSessionPtr session{
             new HttpSession(std::move(socket), GetRequestHandler())
           };
           session->Start();
         }
 
-        DoAccept();
+        AsyncAccept();
       });
 }
 
-void HttpServer::DoAwaitStop() {
+void HttpServer::AsyncAwaitStop() {
   signals_.async_wait(
       [this](boost::system::error_code, int /*signo*/) {
         // The server is stopped by canceling all outstanding asynchronous
diff --git a/src/webcc/http_server.h b/src/webcc/http_server.h
index 098897c..fa47ef7 100644
--- a/src/webcc/http_server.h
+++ b/src/webcc/http_server.h
@@ -26,17 +26,17 @@ public:
 
   HttpServer(unsigned short port, std::size_t workers);
 
-  virtual ~HttpServer();
+  virtual ~HttpServer() = default;
 
   // Run the server's io_service loop.
   void Run();
 
 private:
   // Initiate an asynchronous accept operation.
-  void DoAccept();
+  void AsyncAccept();
 
   // Wait for a request to stop the server.
-  void DoAwaitStop();
+  void AsyncAwaitStop();
 
   // Get the handler for incoming requests.
   virtual HttpRequestHandler* GetRequestHandler() = 0;
diff --git a/src/webcc/http_session.cc b/src/webcc/http_session.cc
index 571fb11..2a5fdb7 100644
--- a/src/webcc/http_session.cc
+++ b/src/webcc/http_session.cc
@@ -17,14 +17,11 @@ HttpSession::HttpSession(boost::asio::ip::tcp::socket socket,
     , request_parser_(&request_) {
 }
 
-HttpSession::~HttpSession() {
-}
-
 void HttpSession::Start() {
-  DoRead();
+  AsyncRead();
 }
 
-void HttpSession::Stop() {
+void HttpSession::Close() {
   boost::system::error_code ec;
   socket_.close(ec);
 }
@@ -35,33 +32,24 @@ void HttpSession::SetResponseContent(std::string&& content,
   response_.SetContentType(content_type);
 }
 
-void HttpSession::SendResponse(int status) {
+void HttpSession::SendResponse(HttpStatus::Enum status) {
   response_.set_status(status);
-  DoWrite();
+  AsyncWrite();
 }
 
-void HttpSession::DoRead() {
+void HttpSession::AsyncRead() {
   socket_.async_read_some(boost::asio::buffer(buffer_),
-                          std::bind(&HttpSession::HandleRead,
+                          std::bind(&HttpSession::ReadHandler,
                                     shared_from_this(),
                                     std::placeholders::_1,
                                     std::placeholders::_2));
 }
 
-void HttpSession::DoWrite() {
-  boost::asio::async_write(socket_,
-                           response_.ToBuffers(),
-                           std::bind(&HttpSession::HandleWrite,
-                                     shared_from_this(),
-                                     std::placeholders::_1,
-                                     std::placeholders::_2));
-}
-
-void HttpSession::HandleRead(boost::system::error_code ec,
-                             std::size_t length) {
+void HttpSession::ReadHandler(boost::system::error_code ec,
+                              std::size_t length) {
   if (ec) {
     if (ec != boost::asio::error::operation_aborted) {
-      Stop();
+      Close();
     }
     return;
   }
@@ -71,13 +59,13 @@ void HttpSession::HandleRead(boost::system::error_code ec,
   if (error != kNoError) {
     // Bad request.
     response_ = HttpResponse::Fault(HttpStatus::kBadRequest);
-    DoWrite();
+    AsyncWrite();
     return;
   }
 
   if (!request_parser_.finished()) {
     // Continue to read the request.
-    DoRead();
+    AsyncRead();
     return;
   }
 
@@ -87,14 +75,23 @@ void HttpSession::HandleRead(boost::system::error_code ec,
   request_handler_->Enqueue(shared_from_this());
 }
 
+void HttpSession::AsyncWrite() {
+  boost::asio::async_write(socket_,
+                           response_.ToBuffers(),
+                           std::bind(&HttpSession::WriteHandler,
+                                     shared_from_this(),
+                                     std::placeholders::_1,
+                                     std::placeholders::_2));
+}
+
 // NOTE:
 // This write handler will be called from main thread (the thread calling
 // io_context.run), even though DoWrite() is invoked by worker threads. This is
 // ensured by Asio.
-void HttpSession::HandleWrite(boost::system::error_code ec,
-                              std::size_t length) {
+void HttpSession::WriteHandler(boost::system::error_code ec,
+                               std::size_t length) {
   if (!ec) {
-    LOG_VERB("Response has been sent back.");
+    LOG_INFO("Response has been sent back.");
 
     // Initiate graceful connection closure.
     boost::system::error_code ec;
@@ -104,7 +101,7 @@ void HttpSession::HandleWrite(boost::system::error_code ec,
     LOG_ERRO("Sending response error: %s", ec.message().c_str());
 
     if (ec != boost::asio::error::operation_aborted) {
-      Stop();
+      Close();
     }
   }
 }
diff --git a/src/webcc/http_session.h b/src/webcc/http_session.h
index b8fd737..6136c22 100644
--- a/src/webcc/http_session.h
+++ b/src/webcc/http_session.h
@@ -23,29 +23,30 @@ public:
   HttpSession(boost::asio::ip::tcp::socket socket,
               HttpRequestHandler* handler);
 
-  ~HttpSession();
+  ~HttpSession() = default;
 
   const HttpRequest& request() const {
     return request_;
   }
 
+  // Start to read and process the client request.
   void Start();
 
-  void Stop();
+  // Close the socket.
+  void Close();
 
   void SetResponseContent(std::string&& content,
                           const std::string& content_type);
 
-  // Write response back to the client with the given HTTP status.
-  void SendResponse(int status);
+  // Send response to client with the given status.
+  void SendResponse(HttpStatus::Enum status);
 
 private:
-  void DoRead();
+  void AsyncRead();
+  void ReadHandler(boost::system::error_code ec, std::size_t length);
 
-  void DoWrite();
-
-  void HandleRead(boost::system::error_code ec, std::size_t length);
-  void HandleWrite(boost::system::error_code ec, std::size_t length);
+  void AsyncWrite();
+  void WriteHandler(boost::system::error_code ec, std::size_t length);
 
 private:
   // Socket for the connection.
diff --git a/src/webcc/logger.h b/src/webcc/logger.h
index 2d0d5f8..92b4fe3 100644
--- a/src/webcc/logger.h
+++ b/src/webcc/logger.h
@@ -3,10 +3,10 @@
 
 // Simple console logger.
 
-namespace webcc {
-
 #if WEBCC_ENABLE_LOG
 
+namespace webcc {
+
 enum LogLevel {
   VERB = 0,
   INFO,
diff --git a/src/webcc/rest_server.cc b/src/webcc/rest_server.cc
index 0b4fc46..61c558e 100644
--- a/src/webcc/rest_server.cc
+++ b/src/webcc/rest_server.cc
@@ -76,7 +76,8 @@ void RestRequestHandler::HandleSession(HttpSessionPtr session) {
   }
 
   // TODO: Only for GET?
-  Url::Query query = Url::SplitQuery(url.query());
+  UrlQuery query;
+  Url::SplitQuery(url.query(), &query);
 
   std::string content;
   bool ok = service->Handle(session->request().method(),
diff --git a/src/webcc/rest_service.h b/src/webcc/rest_service.h
index 49fba3d..9b953ff 100644
--- a/src/webcc/rest_service.h
+++ b/src/webcc/rest_service.h
@@ -10,6 +10,8 @@
 
 namespace webcc {
 
+class UrlQuery;
+
 // Base class for your REST service.
 class RestService {
 public:
@@ -20,12 +22,12 @@ public:
   // \param http_method GET, POST, etc.
   // \param url_sub_matches The regex sub-matches in the URL,
   //                        usually resource ID.
-  // \param query Query parameters in the URL, key value pairs.
+  // \param query Query parameters in the URL.
   // \param request_content Request JSON.
   // \param response_content Output response JSON.
   virtual bool Handle(const std::string& http_method,
                       const std::vector<std::string>& url_sub_matches,
-                      const std::map<std::string, std::string>& query,
+                      const UrlQuery& query,
                       const std::string& request_content,
                       std::string* response_content) = 0;
 };
diff --git a/src/webcc/soap_client.h b/src/webcc/soap_client.h
index 9e842da..1b98bee 100644
--- a/src/webcc/soap_client.h
+++ b/src/webcc/soap_client.h
@@ -28,8 +28,8 @@ protected:
   // -1 means default timeout (normally 30s) will be used.
   int timeout_seconds_ = -1;
 
-  Namespace soapenv_ns_;  // SOAP envelope namespace.
-  Namespace service_ns_;  // Namespace for your web service.
+  SoapNamespace soapenv_ns_;  // SOAP envelope namespace.
+  SoapNamespace service_ns_;  // Namespace for your web service.
 
   // Request URL.
   std::string url_;
diff --git a/src/webcc/soap_message.h b/src/webcc/soap_message.h
index ca2be7e..23b25a1 100644
--- a/src/webcc/soap_message.h
+++ b/src/webcc/soap_message.h
@@ -11,11 +11,11 @@ namespace webcc {
 class SoapMessage {
 public:
   // E.g., set as kSoapEnvNamespace.
-  void set_soapenv_ns(const Namespace& soapenv_ns) {
+  void set_soapenv_ns(const SoapNamespace& soapenv_ns) {
     soapenv_ns_ = soapenv_ns;
   }
 
-  void set_service_ns(const Namespace& service_ns) {
+  void set_service_ns(const SoapNamespace& service_ns) {
     service_ns_ = service_ns;
   }
 
@@ -34,8 +34,7 @@ public:
   bool FromXml(const std::string& xml_string);
 
 protected:
-  SoapMessage() {
-  }
+  SoapMessage() = default;
 
   // Convert to SOAP body XML.
   virtual void ToXmlBody(pugi::xml_node xbody) = 0;
@@ -44,8 +43,8 @@ protected:
   virtual bool FromXmlBody(pugi::xml_node xbody) = 0;
 
 protected:
-  Namespace soapenv_ns_;  // SOAP envelope namespace.
-  Namespace service_ns_;  // Namespace for your web service.
+  SoapNamespace soapenv_ns_;  // SOAP envelope namespace.
+  SoapNamespace service_ns_;  // Namespace for your web service.
 
   std::string operation_;
 };
diff --git a/src/webcc/url.cc b/src/webcc/url.cc
index 810e1bc..a8ecba5 100644
--- a/src/webcc/url.cc
+++ b/src/webcc/url.cc
@@ -1,9 +1,43 @@
 #include "webcc/url.h"
 
+#include <algorithm>
 #include <sstream>
 
 namespace webcc {
 
+////////////////////////////////////////////////////////////////////////////////
+
+void UrlQuery::Add(std::string&& key, std::string&& value) {
+  if (!HasKey(key)) {
+    parameters_.push_back({ std::move(key), std::move(value) });
+  }
+}
+
+void UrlQuery::Remove(const std::string& key) {
+  auto it = Find(key);
+  if (it != parameters_.end()) {
+    parameters_.erase(it);
+  }
+}
+
+const std::string& UrlQuery::GetValue(const std::string& key) const {
+  static const std::string kEmptyValue;
+
+  auto it = Find(key);
+  if (it != parameters_.end()) {
+    return it->value();
+  }
+  return kEmptyValue;
+}
+
+UrlQuery::ConstIterator UrlQuery::Find(const std::string& key) const {
+  return std::find_if(parameters_.begin(),
+                      parameters_.end(),
+                      [&key](const Parameter& p) { return p.key() == key; });
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
 Url::Url(const std::string& str) {
   std::size_t pos = str.find('?');
   if (pos == std::string::npos) {
@@ -44,33 +78,29 @@ static bool SplitKeyValue(const std::string& kv,
 }
 
 // static
-Url::Query Url::SplitQuery(const std::string& query) {
+void Url::SplitQuery(const std::string& str, UrlQuery* query) {
   const std::size_t NPOS = std::string::npos;
 
-  Query result;
-
   // Split into key value pairs separated by '&'.
   std::size_t i = 0;
   while (i != NPOS) {
-    std::size_t j = query.find_first_of('&', i);
+    std::size_t j = str.find_first_of('&', i);
 
     std::string kv;
     if (j == NPOS) {
-      kv = query.substr(i);
+      kv = str.substr(i);
       i = NPOS;
     } else {
-      kv = query.substr(i, j - i);
+      kv = str.substr(i, j - i);
       i = j + 1;
     }
 
     std::string key;
     std::string value;
     if (SplitKeyValue(kv, &key, &value)) {
-      result[key] = value;  // TODO: Move
+      query->Add(std::move(key), std::move(value));
     }
   }
-
-  return result;
 }
 
 }  // namespace webcc
diff --git a/src/webcc/url.h b/src/webcc/url.h
index d37bd3b..2c61306 100644
--- a/src/webcc/url.h
+++ b/src/webcc/url.h
@@ -11,8 +11,37 @@
 #include <string>
 #include <vector>
 
+#include "webcc/common.h"
+
 namespace webcc {
 
+////////////////////////////////////////////////////////////////////////////////
+
+// URL query parameters.
+class UrlQuery {
+public:
+  typedef std::vector<Parameter> Parameters;
+
+  void Add(std::string&& key, std::string&& value);
+
+  void Remove(const std::string& key);
+
+  const std::string& GetValue(const std::string& key) const;
+
+  bool HasKey(const std::string& key) const {
+    return Find(key) != parameters_.end();
+  }
+
+private:
+  typedef Parameters::const_iterator ConstIterator;
+  ConstIterator Find(const std::string& key) const;
+
+private:
+  Parameters parameters_;
+};
+
+////////////////////////////////////////////////////////////////////////////////
+
 class Url {
 public:
   typedef std::map<std::string, std::string> Query;
@@ -40,8 +69,8 @@ public:
   // Split a path into its hierarchical components.
   static std::vector<std::string> SplitPath(const std::string& path);
 
-  // Split query string into key-value map.
-  static Query SplitQuery(const std::string& query);
+  // Split query string into key-value parameters.
+  static void SplitQuery(const std::string& str, UrlQuery* query);
 
 private:
   std::string path_;
diff --git a/src/webcc/utility.cc b/src/webcc/utility.cc
index 4a3c2fe..e2e2dd3 100644
--- a/src/webcc/utility.cc
+++ b/src/webcc/utility.cc
@@ -7,7 +7,6 @@ namespace webcc {
 
 // Print the resolved endpoints.
 // NOTE: Endpoint is one word, don't use "end point".
-// TODO
 void DumpEndpoints(tcp::resolver::results_type& endpoints) {
   std::cout << "Endpoints: " << endpoints.size() << std::endl;