message: Fix recv_packet retval.
diff: @@ -1208,7 +1208,7 @@ ssize_t Socket::recv_packet()
  retval = recv(read_buffer->str + read_buffer->length, header_len - read_buffer->length);
  if (retval <= 0)
  {
  - return 0;
  + return retval;
  }
  else
  {
  