diff --git a/examples/file_upload_client.cc b/examples/file_upload_client.cc
index e2ec736..495f6ac 100644
--- a/examples/file_upload_client.cc
+++ b/examples/file_upload_client.cc
@@ -14,9 +14,13 @@ bool kSslVerify = true;
 #endif
 
 void Help(const char* argv0) {
-  std::cout << "Usage: " << argv0 << " <upload_dir>" << std::endl;
+  std::cout << "Usage: " << argv0 << " <upload_dir> [url]" << std::endl;
+  std::cout << "Default Url: http://httpbin.org/post" << std::endl;
   std::cout << "  E.g.," << std::endl;
   std::cout << "    " << argv0 << "E:/github/webcc/data/upload" << std::endl;
+  std::cout << "    " << argv0
+            << "E:/github/webcc/data/upload http://httpbin.org/post"
+            << std::endl;
 }
 
 int main(int argc, char* argv[]) {
@@ -29,6 +33,13 @@ int main(int argc, char* argv[]) {
 
   const webcc::Path upload_dir(argv[1]);
 
+  std::string url;
+  if (argc == 3) {
+    url = argv[2];
+  } else {
+    url = "http://httpbin.org/post";
+  }
+
   namespace bfs = boost::filesystem;
 
   if (!bfs::is_directory(upload_dir) || !bfs::exists(upload_dir)) {
@@ -38,9 +49,6 @@ int main(int argc, char* argv[]) {
 
   webcc::HttpClientSession session;
 
-  //std::string url = "http://httpbin.org/post";
-  std::string url = "http://localhost:8080/upload";
-
   try {
     auto r = session.PostFile(url, "file",
                               upload_dir / "remember.txt");
diff --git a/examples/file_upload_server.cc b/examples/file_upload_server.cc
index e2922f7..5364684 100644
--- a/examples/file_upload_server.cc
+++ b/examples/file_upload_server.cc
@@ -12,11 +12,11 @@ public:
   void Handle(const webcc::RestRequest& request,
               webcc::RestResponse* response) final {
     if (request.http->method() == webcc::http::methods::kPost) {
-      std::cout << "files: " << request.http->files().size() << std::endl;
+      std::cout << "files: " << request.http->form_parts().size() << std::endl;
 
-      for (auto& pair : request.http->files()) {
-        std::cout << "name: " << pair.first << std::endl;
-        std::cout << "data: " << std::endl << pair.second.data() << std::endl;
+      for (auto& file : request.http->form_parts()) {
+        std::cout << "name: " << file.name() << std::endl;
+        std::cout << "data: " << std::endl << file.data() << std::endl;
       }
 
       response->content = "OK";
diff --git a/examples/http_client.cc b/examples/http_client.cc
index aed97e2..02b8dec 100644
--- a/examples/http_client.cc
+++ b/examples/http_client.cc
@@ -18,8 +18,8 @@ void ExampleBasic() {
   auto r = session.Request(webcc::HttpRequestBuilder{}
                                .Get()
                                .Url("http://httpbin.org/get")
-                               .Parameter("key1", "value1")
-                               .Parameter("key2", "value2")
+                               .Query("key1", "value1")
+                               .Query("key2", "value2")
                                .Header("Accept", "application/json")());
 
   std::cout << r->content() << std::endl;
@@ -44,7 +44,7 @@ void ExampleHttps() {
   auto r = session.Request(webcc::HttpRequestBuilder{}
                                .Get()
                                .Url("https://httpbin.org/get")
-                               .Parameter("key1", "value1")
+                               .Query("key1", "value1")
                                .Header("Accept", "application/json")());
 
   std::cout << r->content() << std::endl;
diff --git a/webcc/CMakeLists.txt b/webcc/CMakeLists.txt
index e89644e..0558b06 100644
--- a/webcc/CMakeLists.txt
+++ b/webcc/CMakeLists.txt
@@ -22,7 +22,6 @@ set(HEADERS
     http_client_session.h
     http_connection.h
     http_connection_pool.h
-    http_file.h
     http_message.h
     http_parser.h
     http_request.h
@@ -53,7 +52,6 @@ set(SOURCES
     http_client_session.cc
     http_connection.cc
     http_connection_pool.cc
-    http_file.cc
     http_message.cc
     http_parser.cc
     http_request.cc
diff --git a/webcc/common.cc b/webcc/common.cc
index 668769f..39d7871 100644
--- a/webcc/common.cc
+++ b/webcc/common.cc
@@ -1,13 +1,25 @@
 #include "webcc/common.h"
 
 #include "boost/algorithm/string.hpp"
+#include "boost/filesystem/fstream.hpp"
 
 #include "webcc/logger.h"
 
+namespace bfs = boost::filesystem;
+
 namespace webcc {
 
 // -----------------------------------------------------------------------------
 
+namespace misc_strings {
+
+const char HEADER_SEPARATOR[] = { ':', ' ' };
+const char CRLF[] = { '\r', '\n' };
+
+}  // misc_strings
+
+// -----------------------------------------------------------------------------
+
 bool Split2(const std::string& str, char token, std::string* part1,
             std::string* part2) {
   std::size_t pos = str.find(token);
@@ -24,6 +36,20 @@ bool Split2(const std::string& str, char token, std::string* part1,
   return true;
 }
 
+bool ReadFile(const Path& path, std::string* output) {
+  bfs::ifstream ifs{ path, std::ios::binary | std::ios::ate };
+  if (!ifs) {
+    return false;
+  }
+
+  auto size = ifs.tellg();
+  output->resize(static_cast<std::size_t>(size), '\0');
+  ifs.seekg(0);
+  ifs.read(&(*output)[0], size);  // TODO: Error handling
+
+  return true;
+}
+
 // -----------------------------------------------------------------------------
 
 void HttpHeaders::Set(const std::string& key, const std::string& value) {
@@ -169,4 +195,76 @@ bool ContentDisposition::Init(const std::string& str) {
   return true;
 }
 
+// -----------------------------------------------------------------------------
+
+FormPart::FormPart(const std::string& name, const Path& path,
+                   const std::string& mime_type)
+    : name_(name), mime_type_(mime_type) {
+  if (!ReadFile(path, &data_)) {
+    throw Exception(kFileIOError, "Cannot read the file.");
+  }
+
+  // Determine file name from file path.
+  // TODO: Encoding
+  file_name_ = path.filename().string();
+
+  // Determine content type from file extension.
+  if (mime_type_.empty()) {
+    std::string extension = path.extension().string();
+    mime_type_ = http::media_types::FromExtension(extension, false);
+  }
+}
+
+FormPart::FormPart(std::string&& data, const std::string& file_name,
+                   const std::string& mime_type) {
+  data_ = std::move(data);
+
+  file_name_ = file_name;
+
+  mime_type_ = mime_type;
+
+  // Determine content type from file extension.
+  if (mime_type_.empty()) {
+    std::size_t pos = file_name_.find_last_of('.');
+    if (pos != std::string::npos) {
+      std::string extension = file_name_.substr(pos + 1);
+      mime_type_ = http::media_types::FromExtension(extension, false);
+    }
+  }
+}
+
+void FormPart::Prepare(std::vector<boost::asio::const_buffer>& payload) {
+  if (headers_.empty()) {
+    std::string value = "form-data";
+    if (!name_.empty()) {
+      value.append("; name=\"" + name_ + "\"");
+    }
+    if (!file_name_.empty()) {
+      value.append("; filename=\"" + file_name_ + "\"");
+    }
+    headers_.Set(http::headers::kContentDisposition, value);
+
+    if (!mime_type_.empty()) {
+      headers_.Set(http::headers::kContentType, mime_type_);
+    }
+  }
+
+  using boost::asio::buffer;
+
+  for (const HttpHeader& h : headers_.data()) {
+    payload.push_back(buffer(h.first));
+    payload.push_back(buffer(misc_strings::HEADER_SEPARATOR));
+    payload.push_back(buffer(h.second));
+    payload.push_back(buffer(misc_strings::CRLF));
+  }
+
+  payload.push_back(buffer(misc_strings::CRLF));
+
+  if (!data_.empty()) {
+    payload.push_back(buffer(data_));
+  }
+
+  payload.push_back(buffer(misc_strings::CRLF));
+}
+
 }  // namespace webcc
diff --git a/webcc/common.h b/webcc/common.h
index bf84058..d458b32 100644
--- a/webcc/common.h
+++ b/webcc/common.h
@@ -6,14 +6,28 @@
 #include <utility>
 #include <vector>
 
+#include "boost/asio/buffer.hpp"  // for const_buffer
+#include "boost/filesystem/path.hpp"
+
+#include "webcc/globals.h"
+
 namespace webcc {
 
 // -----------------------------------------------------------------------------
 
+using Path = boost::filesystem::path;
+
+using Payload = std::vector<boost::asio::const_buffer>;
+
+// -----------------------------------------------------------------------------
+
 // Split a string to two parts by the given token.
 bool Split2(const std::string& str, char token, std::string* part1,
             std::string* part2);
 
+// Read entire file into string.
+bool ReadFile(const Path& path, std::string* output);
+
 // -----------------------------------------------------------------------------
 
 typedef std::pair<std::string, std::string> HttpHeader;
@@ -24,6 +38,10 @@ public:
     return headers_.size();
   }
 
+  bool empty() const {
+    return headers_.empty();
+  }
+
   const std::vector<HttpHeader>& data() const {
     return headers_;
   }
@@ -131,6 +149,95 @@ private:
   bool valid_ = false;
 };
 
+// -----------------------------------------------------------------------------
+
+// Form data part.
+class FormPart {
+public:
+  FormPart() = default;
+
+  explicit FormPart(const std::string& name, const Path& path,
+                    const std::string& mime_type = "");
+
+  FormPart(std::string&& data, const std::string& file_name,
+           const std::string& mime_type = "");
+
+#if WEBCC_DEFAULT_MOVE_COPY_ASSIGN
+
+  FormPart(FormPart&&) = default;
+  FormPart& operator=(FormPart&&) = default;
+
+#else
+
+  FormPart(FormPart&& rhs)
+      : name_(std::move(rhs.name_)),
+        file_name_(std::move(rhs.file_name_)),
+        mime_type_(std::move(rhs.mime_type_)),
+        data_(std::move(rhs.data_)) {
+  }
+
+  FormPart& operator=(FormPart&& rhs) {
+    if (&rhs != this) {
+      name_ = std::move(rhs.name_);
+      file_name_ = std::move(rhs.file_name_);
+      mime_type_ = std::move(rhs.mime_type_);
+      data_ = std::move(rhs.data_);
+    }
+    return *this;
+  }
+
+#endif  // WEBCC_DEFAULT_MOVE_COPY_ASSIGN
+
+  const std::string& name() const {
+    return name_;
+  }
+
+  void set_name(const std::string& name) {
+    name_ = name;
+  }
+
+  const std::string& file_name() const {
+    return file_name_;
+  }
+
+  void set_file_name(const std::string& file_name) {
+    file_name_ = file_name;
+  }
+
+  const std::string& mime_type() const {
+    return mime_type_;
+  }
+
+  const std::string& data() const {
+    return data_;
+  }
+
+  void AppendData(const std::string& data) {
+    data_.append(data);
+  }
+
+  void AppendData(const char* data, std::size_t size) {
+    data_.append(data, size);
+  }
+
+  void Prepare(Payload& payload);
+
+private:
+  std::string name_;
+
+  // E.g., example.jpg
+  // TODO: Unicode
+  std::string file_name_;
+
+  // E.g., image/jpeg
+  std::string mime_type_;
+
+  HttpHeaders headers_;
+
+  // Binary file data.
+  std::string data_;
+};
+
 }  // namespace webcc
 
 #endif  // WEBCC_COMMON_H_
diff --git a/webcc/http_client_session.cc b/webcc/http_client_session.cc
index ca41c94..06588a5 100644
--- a/webcc/http_client_session.cc
+++ b/webcc/http_client_session.cc
@@ -45,7 +45,7 @@ HttpResponsePtr HttpClientSession::Get(
 
   assert(parameters.size() % 2 == 0);
   for (std::size_t i = 1; i < parameters.size(); i += 2) {
-    builder.Parameter(parameters[i - 1], parameters[i]);
+    builder.Query(parameters[i - 1], parameters[i]);
   }
 
   SetHeaders(headers, &builder);
diff --git a/webcc/http_connection.cc b/webcc/http_connection.cc
index 25bb81a..e8604d6 100644
--- a/webcc/http_connection.cc
+++ b/webcc/http_connection.cc
@@ -95,7 +95,7 @@ void HttpConnection::OnRead(boost::system::error_code ec, std::size_t length) {
 void HttpConnection::DoWrite() {
   LOG_VERB("HTTP response:\n%s", response_->Dump(4, "> ").c_str());
 
-  boost::asio::async_write(socket_, response_->ToBuffers(),
+  boost::asio::async_write(socket_, response_->payload(),
                            std::bind(&HttpConnection::OnWrite, shared_from_this(),
                                      std::placeholders::_1,
                                      std::placeholders::_2));
diff --git a/webcc/http_file.cc b/webcc/http_file.cc
deleted file mode 100644
index 50466aa..0000000
--- a/webcc/http_file.cc
+++ /dev/null
@@ -1,64 +0,0 @@
-#include "webcc/http_file.h"
-
-#include "boost/filesystem/fstream.hpp"
-
-namespace bfs = boost::filesystem;
-
-namespace webcc {
-
-// -----------------------------------------------------------------------------
-
-// Read entire file into string.
-static bool ReadFile(const Path& path, std::string* output) {
-  bfs::ifstream ifs{path, std::ios::binary | std::ios::ate};
-  if (!ifs) {
-    return false;
-  }
-
-  auto size = ifs.tellg();
-  output->resize(static_cast<std::size_t>(size), '\0');
-  ifs.seekg(0);
-  ifs.read(&(*output)[0], size);  // TODO: Error handling
-
-  return true;
-}
-
-// -----------------------------------------------------------------------------
-
-HttpFile::HttpFile(const Path& path, const std::string& mime_type) {
-  if (!ReadFile(path, &data_)) {
-    throw Exception(kFileIOError, "Cannot read the file.");
-  }
-
-  // Determine file name from file path.
-  // TODO: Encoding
-  file_name_ = path.filename().string();
-
-  // Determine content type from file extension.
-  if (mime_type.empty()) {
-    std::string extension = path.extension().string();
-    mime_type_ = http::media_types::FromExtension(extension, false);
-  } else {
-    mime_type_ = mime_type;
-  }
-}
-
-HttpFile::HttpFile(std::string&& data, const std::string& file_name,
-                   const std::string& mime_type) {
-  data_ = std::move(data);
-
-  file_name_ = file_name;
-
-  mime_type_ = mime_type;
-
-  // Determine content type from file extension.
-  if (mime_type_.empty()) {
-    std::size_t pos = file_name_.find_last_of('.');
-    if (pos != std::string::npos) {
-      std::string extension = file_name_.substr(pos + 1);
-      mime_type_ = http::media_types::FromExtension(extension, false);
-    }
-  }
-}
-
-}  // namespace webcc
diff --git a/webcc/http_file.h b/webcc/http_file.h
deleted file mode 100644
index 98c5105..0000000
--- a/webcc/http_file.h
+++ /dev/null
@@ -1,87 +0,0 @@
-#ifndef WEBCC_HTTP_FILE_H_
-#define WEBCC_HTTP_FILE_H_
-
-#include <string>
-
-#include "boost/filesystem/path.hpp"
-
-#include "webcc/globals.h"
-
-namespace webcc {
-
-using Path = boost::filesystem::path;
-
-// File for HTTP transfer (upload/download).
-class HttpFile {
-public:
-  HttpFile() = default;
-
-  explicit HttpFile(const Path& path, const std::string& mime_type = "");
-
-  HttpFile(std::string&& data, const std::string& file_name,
-           const std::string& mime_type = "");
-
-#if WEBCC_DEFAULT_MOVE_COPY_ASSIGN
-
-  HttpFile(HttpFile&&) = default;
-  HttpFile& operator=(HttpFile&&) = default;
-
-#else
-
-  HttpFile(HttpFile&& rhs)
-      : data_(std::move(rhs.data_)),
-        file_name_(std::move(rhs.file_name_)),
-        mime_type_(std::move(rhs.mime_type_)) {
-  }
-
-  HttpFile& operator=(HttpFile&& rhs) {
-    if (&rhs != this) {
-      data_ = std::move(rhs.data_);
-      file_name_ = std::move(rhs.file_name_);
-      mime_type_ = std::move(rhs.mime_type_);
-    }
-    return *this;
-  }
-
-#endif  // WEBCC_DEFAULT_MOVE_COPY_ASSIGN
-
-  const std::string& data() const {
-    return data_;
-  }
-
-  void AppendData(const std::string& data) {
-    data_.append(data);
-  }
-
-  void AppendData(const char* data, std::size_t size) {
-    data_.append(data, size);
-  }
-
-  const std::string& file_name() const {
-    return file_name_;
-  }
-
-  void set_file_name(const std::string& file_name) {
-    file_name_ = file_name;
-  }
-
-  const std::string& mime_type() const {
-    return mime_type_;
-  }
-
-private:
-  // Binary file data.
-  // TODO: don't use std::string?
-  std::string data_;
-
-  // E.g., example.jpg
-  // TODO: Unicode
-  std::string file_name_;
-
-  // E.g., image/jpeg
-  std::string mime_type_;
-};
-
-}  // namespace webcc
-
-#endif  // WEBCC_HTTP_FILE_H_
diff --git a/webcc/http_message.cc b/webcc/http_message.cc
index 1f9c766..25c8063 100644
--- a/webcc/http_message.cc
+++ b/webcc/http_message.cc
@@ -13,7 +13,7 @@ namespace webcc {
 
 namespace misc_strings {
 
-const char NAME_VALUE_SEPARATOR[] = { ':', ' ' };
+const char HEADER_SEPARATOR[] = { ':', ' ' };
 const char CRLF[] = { '\r', '\n' };
 
 }  // misc_strings
@@ -79,28 +79,28 @@ void HttpMessage::SetContent(std::string&& content, bool set_length) {
   }
 }
 
-// ATTENTION: The buffers don't hold the memory!
-std::vector<boost::asio::const_buffer> HttpMessage::ToBuffers() const {
+void HttpMessage::Prepare() {
   assert(!start_line_.empty());
 
-  std::vector<boost::asio::const_buffer> buffers;
+  using boost::asio::buffer;
 
-  buffers.push_back(boost::asio::buffer(start_line_));
+  payload_.clear();
+
+  payload_.push_back(buffer(start_line_));
+  payload_.push_back(buffer(misc_strings::CRLF));
 
   for (const HttpHeader& h : headers_.data()) {
-    buffers.push_back(boost::asio::buffer(h.first));
-    buffers.push_back(boost::asio::buffer(misc_strings::NAME_VALUE_SEPARATOR));
-    buffers.push_back(boost::asio::buffer(h.second));
-    buffers.push_back(boost::asio::buffer(misc_strings::CRLF));
+    payload_.push_back(buffer(h.first));
+    payload_.push_back(buffer(misc_strings::HEADER_SEPARATOR));
+    payload_.push_back(buffer(h.second));
+    payload_.push_back(buffer(misc_strings::CRLF));
   }
 
-  buffers.push_back(boost::asio::buffer(misc_strings::CRLF));
+  payload_.push_back(buffer(misc_strings::CRLF));
 
-  if (content_length_ > 0) {
-    buffers.push_back(boost::asio::buffer(content_));
+  if (!content_.empty()) {
+    payload_.push_back(buffer(content_));
   }
-
-  return buffers;
 }
 
 void HttpMessage::Dump(std::ostream& os, std::size_t indent,
@@ -111,7 +111,7 @@ void HttpMessage::Dump(std::ostream& os, std::size_t indent,
   }
   indent_str.append(prefix);
 
-  os << indent_str << start_line_;
+  os << indent_str << start_line_ << std::endl;
 
   for (const HttpHeader& h : headers_.data()) {
     os << indent_str << h.first << ": " << h.second << std::endl;
diff --git a/webcc/http_message.h b/webcc/http_message.h
index e271bd8..d6846d2 100644
--- a/webcc/http_message.h
+++ b/webcc/http_message.h
@@ -6,10 +6,7 @@
 #include <utility>  // for move()
 #include <vector>
 
-#include "boost/asio/buffer.hpp"  // for const_buffer
-
 #include "webcc/common.h"
-#include "webcc/http_file.h"
 #include "webcc/globals.h"
 
 namespace webcc {
@@ -84,14 +81,12 @@ public:
 
   void SetContent(std::string&& content, bool set_length);
 
-  // Make the message (e.g., update start line).
-  // Must be called before ToBuffers()!
-  virtual bool Prepare() = 0;
+  // Prepare payload.
+  virtual void Prepare();
 
-  // Convert the message into a vector of buffers. The buffers do not own the
-  // underlying memory blocks, therefore the message object must remain valid
-  // and not be changed until the write operation has completed.
-  std::vector<boost::asio::const_buffer> ToBuffers() const;
+  const Payload& payload() const {
+    return payload_;
+  }
 
   // Dump to output stream.
   void Dump(std::ostream& os, std::size_t indent = 0,
@@ -119,6 +114,9 @@ protected:
   std::size_t content_length_;
 
   HttpHeaders headers_;
+
+  // NOTE: The payload itself doesn't hold the memory!
+  Payload payload_;
 };
 
 }  // namespace webcc
diff --git a/webcc/http_parser.h b/webcc/http_parser.h
index 60ea968..7094d0e 100644
--- a/webcc/http_parser.h
+++ b/webcc/http_parser.h
@@ -3,14 +3,14 @@
 
 #include <string>
 
+#include "webcc/common.h"
 #include "webcc/globals.h"
-#include "webcc/http_file.h"
 
 namespace webcc {
 
 class HttpMessage;
 
-// HttpParser parses HTTP request and response.
+// HTTP request and response parser.
 class HttpParser {
 public:
   explicit HttpParser(HttpMessage* message);
@@ -80,19 +80,6 @@ protected:
   bool chunked_;
   std::size_t chunk_size_;
   bool finished_;
-
-  struct Part {
-    enum Step {
-      kStart,
-      kBoundaryParsed,
-      kHeadersParsed,
-      kEnded,
-    };
-    Step step = kStart;
-    std::string name;
-    HttpFile file;
-  };
-  Part part_;
 };
 
 }  // namespace webcc
diff --git a/webcc/http_request.cc b/webcc/http_request.cc
index 32e1d03..491c0e1 100644
--- a/webcc/http_request.cc
+++ b/webcc/http_request.cc
@@ -1,13 +1,84 @@
 #include "webcc/http_request.h"
 
 #include "webcc/logger.h"
+#include "webcc/utility.h"
 
 namespace webcc {
 
-bool HttpRequest::Prepare() {
+// -----------------------------------------------------------------------------
+
+namespace misc_strings {
+
+const char CRLF[] = { '\r', '\n' };
+const char DOUBLE_DASHES[] = { '-', '-' };
+
+}  // misc_strings
+
+// -----------------------------------------------------------------------------
+
+void HttpRequest::Prepare() {
+  CreateStartLine();
+
+  if (url_.port().empty()) {
+    SetHeader(http::headers::kHost, url_.host());
+  } else {
+    SetHeader(http::headers::kHost, url_.host() + ":" + url_.port());
+  }
+
+  if (form_parts_.empty()) {
+    HttpMessage::Prepare();
+  } else {
+    // Multipart form data.
+
+    // Another choice to generate the boundary is what Apache does.
+    // See: https://stackoverflow.com/a/5686863
+    if (boundary_.empty()) {
+      boundary_ = RandomUuid();
+    }
+
+    SetContentType("multipart/form-data; boundary=" + boundary_);
+
+    Payload data_payload;
+
+    using boost::asio::buffer;
+
+    for (auto& part : form_parts_) {
+      // Boundary
+      data_payload.push_back(buffer(misc_strings::DOUBLE_DASHES));
+      data_payload.push_back(buffer(boundary_));
+      data_payload.push_back(buffer(misc_strings::CRLF));
+
+      part.Prepare(data_payload);
+    }
+
+    // Boundary end
+    data_payload.push_back(buffer(misc_strings::DOUBLE_DASHES));
+    data_payload.push_back(buffer(boundary_));
+    data_payload.push_back(buffer(misc_strings::DOUBLE_DASHES));
+    data_payload.push_back(buffer(misc_strings::CRLF));
+
+    // Update Content-Length header.
+    std::size_t content_length = 0;
+    for (auto& buffer : data_payload) {
+      content_length += buffer.size();
+    }
+    SetContentLength(content_length);
+
+    // Prepare start line and headers.
+    HttpMessage::Prepare();
+
+    // Append payload of content data.
+    payload_.insert(payload_.end(), data_payload.begin(), data_payload.end());
+  }
+}
+
+void HttpRequest::CreateStartLine() {
+  if (!start_line_.empty()) {
+    return;
+  }
+
   if (url_.host().empty()) {
-    LOG_ERRO("Invalid request: host is missing.");
-    return false;
+    throw Exception(kSchemaError, "Invalid request: host is missing.");
   }
 
   std::string target = "/" + url_.path();
@@ -20,15 +91,6 @@ bool HttpRequest::Prepare() {
   start_line_ += " ";
   start_line_ += target;
   start_line_ += " HTTP/1.1";
-  start_line_ += kCRLF;
-
-  if (url_.port().empty()) {
-    SetHeader(http::headers::kHost, url_.host());
-  } else {
-    SetHeader(http::headers::kHost, url_.host() + ":" + url_.port());
-  }
-
-  return true;
 }
 
 }  // namespace webcc
diff --git a/webcc/http_request.h b/webcc/http_request.h
index 7df564d..8b6eecc 100644
--- a/webcc/http_request.h
+++ b/webcc/http_request.h
@@ -1,7 +1,6 @@
 #ifndef WEBCC_HTTP_REQUEST_H_
 #define WEBCC_HTTP_REQUEST_H_
 
-#include <map>
 #include <memory>
 #include <string>
 #include <vector>
@@ -32,9 +31,8 @@ public:
     url_.Init(url);
   }
 
-  // Add URL query parameter.
-  void AddParameter(const std::string& key, const std::string& value) {
-    url_.AddParameter(key, value);
+  void AddQuery(const std::string& key, const std::string& value) {
+    url_.AddQuery(key, value);
   }
 
   const std::string& method() const {
@@ -57,18 +55,23 @@ public:
     return port().empty() ? default_port : port();
   }
 
-  const std::map<std::string, HttpFile>& files() const {
-    return files_;
+  const std::vector<FormPart>& form_parts() const {
+    return form_parts_;
   }
 
-  // Add a file to upload.
-  void AddFile(const std::string& name, HttpFile&& file) {
-    files_[name] = std::move(file);
+  void set_form_parts_(std::vector<FormPart>&& form_parts) {
+    form_parts_ = std::move(form_parts);
+  }
+
+  void AddFormPart(FormPart&& form_part) {
+    form_parts_.push_back(std::move(form_part));
   }
 
   // Prepare payload.
-  // Compose start line, set Host header, etc.
-  bool Prepare() final;
+  void Prepare() final;
+
+private:
+  void CreateStartLine();
 
 private:
   std::string method_;
@@ -76,7 +79,9 @@ private:
   Url url_;
 
   // Files to upload for a POST request.
-  std::map<std::string, HttpFile> files_;
+  std::vector<FormPart> form_parts_;
+
+  std::string boundary_;
 };
 
 }  // namespace webcc
diff --git a/webcc/http_request_builder.cc b/webcc/http_request_builder.cc
index f43c410..2cd0c60 100644
--- a/webcc/http_request_builder.cc
+++ b/webcc/http_request_builder.cc
@@ -14,7 +14,7 @@ HttpRequestPtr HttpRequestBuilder::Build() {
   auto request = std::make_shared<HttpRequest>(method_, url_);
 
   for (std::size_t i = 1; i < parameters_.size(); i += 2) {
-    request->AddParameter(parameters_[i - 1], parameters_[i]);
+    request->AddQuery(parameters_[i - 1], parameters_[i]);
   }
 
   for (std::size_t i = 1; i < headers_.size(); i += 2) {
@@ -34,17 +34,19 @@ HttpRequestPtr HttpRequestBuilder::Build() {
       request->SetContentType(http::media_types::kApplicationJson, "");
     }
   } else if (!files_.empty()) {
-    // Another choice to generate the boundary is what Apache does, see:
-    //   https://stackoverflow.com/a/5686863
-    const std::string boundary = RandomUuid();
+    request->set_form_parts_(std::move(files_));
 
-    request->SetContentType("multipart/form-data; boundary=" + boundary);
+    //// Another choice to generate the boundary is what Apache does.
+    //// See: https://stackoverflow.com/a/5686863
+    //const std::string boundary = RandomUuid();
 
-    std::string data;
-    CreateFormData(&data, boundary);
+    //request->SetContentType("multipart/form-data; boundary=" + boundary);
 
-    // Ingore gzip since most servers don't support it.
-    request->SetContent(std::move(data), true);
+    //std::string data;
+    //CreateFormData(&data, boundary);
+
+    //// Ingore gzip since most servers don't support it.
+    //request->SetContent(std::move(data), true);
   }
 
   return request;
@@ -55,7 +57,7 @@ HttpRequestBuilder& HttpRequestBuilder::File(const std::string& name,
                                              const std::string& mime_type) {
   assert(!name.empty());
 
-  files_[name] = HttpFile(path, mime_type);
+  files_.push_back(FormPart{ name, path, mime_type });
 
   return *this;
 }
@@ -66,7 +68,8 @@ HttpRequestBuilder& HttpRequestBuilder::FileData(const std::string& name,
                                                  const std::string& mime_type) {
   assert(!name.empty());
 
-  files_[name] = HttpFile(std::move(file_data), file_name, mime_type);
+  // TODO
+  //files_[name] = HttpFile(std::move(file_data), file_name, mime_type);
 
   return *this;
 }
@@ -100,37 +103,37 @@ void HttpRequestBuilder::SetContent(HttpRequestPtr request,
   request->SetContent(std::move(data), true);
 }
 
-void HttpRequestBuilder::CreateFormData(std::string* data,
-                                        const std::string& boundary) {
-  for (auto& pair : files_) {
-    data->append("--" + boundary + kCRLF);
-
-    // Content-Disposition header
-    data->append("Content-Disposition: form-data");
-    if (!pair.first.empty()) {
-      data->append("; name=\"" + pair.first + "\"");
-    }
-    if (!pair.second.file_name().empty()) {
-      data->append("; filename=\"" + pair.second.file_name() + "\"");
-    }
-    data->append(kCRLF);
-
-    // Content-Type header
-    if (!pair.second.mime_type().empty()) {
-      data->append("Content-Type: " + pair.second.mime_type());
-      data->append(kCRLF);
-    }
-
-    data->append(kCRLF);
-
-    // Payload
-    data->append(pair.second.data());
-
-    data->append(kCRLF);
-  }
-
-  data->append("--" + boundary + "--");
-  data->append(kCRLF);
-}
+//void HttpRequestBuilder::CreateFormData(std::string* data,
+//                                        const std::string& boundary) {
+//  for (auto& pair : files_) {
+//    data->append("--" + boundary + kCRLF);
+//
+//    // Content-Disposition header
+//    data->append("Content-Disposition: form-data");
+//    if (!pair.first.empty()) {
+//      data->append("; name=\"" + pair.first + "\"");
+//    }
+//    if (!pair.second.file_name().empty()) {
+//      data->append("; filename=\"" + pair.second.file_name() + "\"");
+//    }
+//    data->append(kCRLF);
+//
+//    // Content-Type header
+//    if (!pair.second.mime_type().empty()) {
+//      data->append("Content-Type: " + pair.second.mime_type());
+//      data->append(kCRLF);
+//    }
+//
+//    data->append(kCRLF);
+//
+//    // Payload
+//    data->append(pair.second.data());
+//
+//    data->append(kCRLF);
+//  }
+//
+//  data->append("--" + boundary + "--");
+//  data->append(kCRLF);
+//}
 
 }  // namespace webcc
diff --git a/webcc/http_request_builder.h b/webcc/http_request_builder.h
index deabc9c..ff80bdb 100644
--- a/webcc/http_request_builder.h
+++ b/webcc/http_request_builder.h
@@ -5,7 +5,6 @@
 #include <string>
 #include <vector>
 
-#include "webcc/http_file.h"
 #include "webcc/http_request.h"
 
 namespace webcc {
@@ -16,6 +15,11 @@ public:
       : method_(method) {
   }
 
+  ~HttpRequestBuilder() = default;
+
+  HttpRequestBuilder(const HttpRequestBuilder&) = delete;
+  HttpRequestBuilder& operator=(const HttpRequestBuilder&) = delete;
+
   // Build the request.
   HttpRequestPtr Build();
 
@@ -44,8 +48,8 @@ public:
     return *this;
   }
 
-  HttpRequestBuilder& Parameter(const std::string& key,
-                                const std::string& value) {
+  HttpRequestBuilder& Query(const std::string& key,
+                            const std::string& value) {
     parameters_.push_back(key);
     parameters_.push_back(value);
     return *this;
@@ -70,8 +74,8 @@ public:
   HttpRequestBuilder& File(const std::string& name, const Path& path,
                            const std::string& mime_type = "");
 
-  HttpRequestBuilder& File(const std::string& name, HttpFile&& file) {
-    files_[name] = std::move(file);
+  HttpRequestBuilder& File(FormPart&& file) {
+    files_.push_back(std::move(file));
     return *this;
   }
 
@@ -108,7 +112,7 @@ public:
 private:
   void SetContent(HttpRequestPtr request, std::string&& data);
 
-  void CreateFormData(std::string* data, const std::string& boundary);
+  //void CreateFormData(std::string* data, const std::string& boundary);
   
 private:
   std::string method_;
@@ -125,7 +129,7 @@ private:
   bool json_ = false;
 
   // Files to upload for a POST request.
-  std::map<std::string, HttpFile> files_;
+  std::vector<FormPart> files_;
 
   // Compress the request content.
   // NOTE: Most servers don't support compressed requests.
diff --git a/webcc/http_request_parser.cc b/webcc/http_request_parser.cc
index eb8f2ea..6175987 100644
--- a/webcc/http_request_parser.cc
+++ b/webcc/http_request_parser.cc
@@ -61,7 +61,7 @@ bool HttpRequestParser::ParseMultipartContent() {
       break;
     }
 
-    if (part_.step == Part::Step::kStart) {
+    if (step_ == Step::kStart) {
       std::string line;
       if (!GetNextLine(0, &line, true)) {
         break;  // Not enough data
@@ -72,15 +72,15 @@ bool HttpRequestParser::ParseMultipartContent() {
       }
       LOG_INFO("Boundary line: %s", line.c_str());
       // Go to next step.
-      part_.step = Part::Step::kBoundaryParsed;
+      step_ = Step::kBoundaryParsed;
       continue;
     }
 
-    if (part_.step == Part::Step::kBoundaryParsed) {
+    if (step_ == Step::kBoundaryParsed) {
       bool need_more_data = false;
       if (ParsePartHeaders(&need_more_data)) {
         // Go to next step.
-        part_.step = Part::Step::kHeadersParsed;
+        step_ = Step::kHeadersParsed;
         LOG_INFO("Part headers just ended.");
         continue;
       } else {
@@ -93,13 +93,13 @@ bool HttpRequestParser::ParseMultipartContent() {
       }
     }
 
-    if (part_.step == Part::Step::kHeadersParsed) {
+    if (step_ == Step::kHeadersParsed) {
       std::size_t off = 0;
       std::size_t count = 0;
       bool ended = false;
       if (!GetNextBoundaryLine(&off, &count, &ended)) {
         // All pending data belongs to this part.
-        part_.file.AppendData(pending_data_);
+        part_.AppendData(pending_data_);
         pending_data_.clear();
         break;
       }
@@ -109,24 +109,24 @@ bool HttpRequestParser::ParseMultipartContent() {
       // This part has ended.
       if (off > 2) {
         // -2 for exluding the CRLF after the data.
-        part_.file.AppendData(pending_data_.data(), off - 2);
+        part_.AppendData(pending_data_.data(), off - 2);
       }
 
-      request_->AddFile(part_.name, std::move(part_.file));
+      request_->AddFormPart(std::move(part_));
 
       if (ended) {
         // Go to the end step.
-        part_.step = Part::Step::kEnded;
+        step_ = Step::kEnded;
         break;
       } else {
         // Go to next step.
-        part_.step = Part::Step::kBoundaryParsed;
+        step_ = Step::kBoundaryParsed;
         continue;
       }
     }
   }
 
-  if (part_.step == Part::Step::kEnded) {
+  if (step_ == Step::kEnded) {
     LOG_INFO("Multipart data has ended.");
     Finish();
   }
@@ -169,10 +169,10 @@ bool HttpRequestParser::ParsePartHeaders(bool* need_more_data) {
                  header.second.c_str());
         return false;
       }
-      part_.name = content_disposition.name();
-      part_.file.set_file_name(content_disposition.file_name());
+      part_.set_name(content_disposition.name());
+      part_.set_file_name(content_disposition.file_name());
       LOG_INFO("Content-Disposition (name=%s; filename=%s)",
-               part_.name.c_str(), part_.file.file_name().c_str());
+               part_.name().c_str(), part_.file_name().c_str());
     }
 
     // TODO: Parse other headers.
diff --git a/webcc/http_request_parser.h b/webcc/http_request_parser.h
index 8e27584..efc2f32 100644
--- a/webcc/http_request_parser.h
+++ b/webcc/http_request_parser.h
@@ -34,6 +34,16 @@ private:
 
 private:
   HttpRequest* request_;
+
+  enum Step {
+    kStart,
+    kBoundaryParsed,
+    kHeadersParsed,
+    kEnded,
+  };
+  Step step_ = kStart;
+
+  FormPart part_;
 };
 
 }  // namespace webcc
diff --git a/webcc/http_response.cc b/webcc/http_response.cc
index 493d1a9..dbc1739 100644
--- a/webcc/http_response.cc
+++ b/webcc/http_response.cc
@@ -6,17 +6,17 @@ namespace webcc {
 
 namespace status_strings {
 
-const std::string OK = "HTTP/1.1 200 OK\r\n";
-const std::string CREATED = "HTTP/1.1 201 Created\r\n";
-const std::string ACCEPTED = "HTTP/1.1 202 Accepted\r\n";
-const std::string NO_CONTENT = "HTTP/1.1 204 No Content\r\n";
-const std::string NOT_MODIFIED = "HTTP/1.1 304 Not Modified\r\n";
-const std::string BAD_REQUEST = "HTTP/1.1 400 Bad Request\r\n";
-const std::string NOT_FOUND = "HTTP/1.1 404 Not Found\r\n";
+const std::string OK = "HTTP/1.1 200 OK";
+const std::string CREATED = "HTTP/1.1 201 Created";
+const std::string ACCEPTED = "HTTP/1.1 202 Accepted";
+const std::string NO_CONTENT = "HTTP/1.1 204 No Content";
+const std::string NOT_MODIFIED = "HTTP/1.1 304 Not Modified";
+const std::string BAD_REQUEST = "HTTP/1.1 400 Bad Request";
+const std::string NOT_FOUND = "HTTP/1.1 404 Not Found";
 const std::string INTERNAL_SERVER_ERROR =
-    "HTTP/1.1 500 Internal Server Error\r\n";
-const std::string NOT_IMPLEMENTED = "HTTP/1.1 501 Not Implemented\r\n";
-const std::string SERVICE_UNAVAILABLE = "HTTP/1.1 503 Service Unavailable\r\n";
+    "HTTP/1.1 500 Internal Server Error";
+const std::string NOT_IMPLEMENTED = "HTTP/1.1 501 Not Implemented";
+const std::string SERVICE_UNAVAILABLE = "HTTP/1.1 503 Service Unavailable";
 
 const std::string& ToString(int status) {
   switch (status) {
@@ -57,13 +57,15 @@ const std::string& ToString(int status) {
 
 }  // namespace status_strings
 
-bool HttpResponse::Prepare() {
-  start_line_ = status_strings::ToString(status_);
+void HttpResponse::Prepare() {
+  if (start_line_.empty()) {
+    start_line_ = status_strings::ToString(status_);
+  }
 
   SetHeader(http::headers::kServer, http::UserAgent());
   SetHeader(http::headers::kDate, GetHttpDateTimestamp());
 
-  return true;
+  HttpMessage::Prepare();
 }
 
 }  // namespace webcc
diff --git a/webcc/http_response.h b/webcc/http_response.h
index 88754cd..aafbba7 100644
--- a/webcc/http_response.h
+++ b/webcc/http_response.h
@@ -19,13 +19,17 @@ public:
 
   ~HttpResponse() override = default;
 
-  int status() const { return status_; }
+  int status() const {
+    return status_;
+  }
 
-  void set_status(int status) { status_ = status; }
+  void set_status(int status) {
+    status_ = status;
+  }
 
   // Set start line according to status code.
-  bool Prepare() final;
-  
+  void Prepare() final;
+
 private:
   int status_;
 };
diff --git a/webcc/http_socket.cc b/webcc/http_socket.cc
index aee1a56..206359c 100644
--- a/webcc/http_socket.cc
+++ b/webcc/http_socket.cc
@@ -24,7 +24,7 @@ void HttpSocket::Connect(const std::string& /*host*/,
 
 void HttpSocket::Write(const HttpRequest& request,
                        boost::system::error_code* ec) {
-  boost::asio::write(socket_, request.ToBuffers(), *ec);
+  boost::asio::write(socket_, request.payload(), *ec);
 }
 
 void HttpSocket::AsyncReadSome(ReadHandler&& handler, std::vector<char>* buffer) {
@@ -60,7 +60,7 @@ void HttpSslSocket::Connect(const std::string& host,
 
 void HttpSslSocket::Write(const HttpRequest& request,
                           boost::system::error_code* ec) {
-  boost::asio::write(ssl_socket_, request.ToBuffers(), *ec);
+  boost::asio::write(ssl_socket_, request.payload(), *ec);
 }
 
 void HttpSslSocket::AsyncReadSome(ReadHandler&& handler, std::vector<char>* buffer) {
diff --git a/webcc/url.cc b/webcc/url.cc
index 76782ae..fcb0be8 100644
--- a/webcc/url.cc
+++ b/webcc/url.cc
@@ -268,7 +268,7 @@ void Url::Init(const std::string& str, bool decode, bool clear) {
   }
 }
 
-void Url::AddParameter(const std::string& key, const std::string& value) {
+void Url::AddQuery(const std::string& key, const std::string& value) {
   if (!query_.empty()) {
     query_ += "&";
   }
diff --git a/webcc/url.h b/webcc/url.h
index ed4fa06..f7bc80f 100644
--- a/webcc/url.h
+++ b/webcc/url.h
@@ -111,8 +111,8 @@ public:
     return query_;
   }
 
-  // Add a parameter to the query string.
-  void AddParameter(const std::string& key, const std::string& value);
+  // Add a query parameter.
+  void AddQuery(const std::string& key, const std::string& value);
 
 private:
   void Parse(const std::string& str);