diff --git a/libwebserv/protocol_handler.cc b/libwebserv/protocol_handler.cc
index 544281f..81f7a5c 100644
--- a/libwebserv/protocol_handler.cc
+++ b/libwebserv/protocol_handler.cc
@@ -31,8 +31,51 @@
 
 namespace {
 
-// A dummy callback for async D-Bus errors.
-void IgnoreError(chromeos::Error* error) {}
+// Dummy callbacks for async D-Bus/Stream errors.
+void IgnoreDBusError(chromeos::Error* error) {}
+void IgnoreStreamError(const chromeos::Error* error) {}
+
+// Structure to hold the data needed for asynchronous copying of two streams.
+struct StreamCopyData {
+  chromeos::StreamPtr src_stream;
+  chromeos::StreamPtr dest_stream;
+  std::vector<uint8_t> buffer;
+};
+
+// Forward-declaration.
+void PerformRead(std::unique_ptr<StreamCopyData> data);
+
+// Async callback which writes data to the destination stream after read.
+void PerformWrite(std::unique_ptr<StreamCopyData> data, size_t size) {
+  if (size == 0) // We are all done.
+    return;
+  data->dest_stream->WriteAllAsync(
+      data->buffer.data(), size, base::Bind(&PerformRead, base::Passed(&data)),
+      base::Bind(&IgnoreStreamError), nullptr);
+}
+
+// Reads the data from the source stream into a buffer and invokes PerformWrite
+// when done.
+void PerformRead(std::unique_ptr<StreamCopyData> data) {
+  data->src_stream->ReadAsync(data->buffer.data(), data->buffer.size(),
+                              base::Bind(&PerformWrite, base::Passed(&data)),
+                              base::Bind(&IgnoreStreamError), nullptr);
+}
+
+// Copies the data from |src_stream| to the destination stream represented
+// by a file descriptor |fd|.
+void WriteResponseData(chromeos::StreamPtr src_stream,
+                       const dbus::FileDescriptor& fd) {
+  std::unique_ptr<StreamCopyData> data{new StreamCopyData};
+  int dupfd = dup(fd.value());
+  data->src_stream = std::move(src_stream);
+  data->dest_stream =
+      chromeos::FileStream::FromFileDescriptor(dupfd, true, nullptr);
+  data->buffer.resize(4096);  // Read buffer of 4 KiB.
+  CHECK(data->src_stream);
+  CHECK(data->dest_stream);
+  PerformRead(std::move(data));
+}
 
 }  // anonymous namespace
 
@@ -129,7 +172,7 @@
     pair.first->RemoveRequestHandlerAsync(
         pair.second,
         base::Bind(&base::DoNothing),
-        base::Bind(&IgnoreError));
+        base::Bind(&IgnoreDBusError));
   }
 
   request_handlers_.erase(p);
@@ -209,7 +252,7 @@
     const std::string& request_id,
     int status_code,
     const std::multimap<std::string, std::string>& headers,
-    const std::vector<uint8_t>& data) {
+    chromeos::StreamPtr data_stream) {
   ProtocolHandlerProxy* proxy = GetRequestProtocolHandlerProxy(request_id);
   if (!proxy)
     return;
@@ -219,9 +262,13 @@
   for (const auto& pair : headers)
     header_list.emplace_back(pair.first, pair.second);
 
-  proxy->CompleteRequestAsync(request_id, status_code, header_list, data,
-                              base::Bind(&base::DoNothing),
-                              base::Bind([](chromeos::Error*) {}));
+  int64_t data_size = -1;
+  if (data_stream->CanGetSize())
+    data_size = data_stream->GetRemainingSize();
+  proxy->CompleteRequestAsync(
+      request_id, status_code, header_list, data_size,
+      base::Bind(&WriteResponseData, base::Passed(&data_stream)),
+      base::Bind(&IgnoreDBusError));
 }
 
 void ProtocolHandler::GetFileData(