linux - C++ socket never ready for write with poll -

i writing c++ wrapper sockets on linux. can connect read/write http server poll function works reading reason won't work writing. have tried using gdb , appears poll sets fd.revents 0 when fd.events pollout

poll code:

/**  *@brief assigns request.reply based on fd.revents  */ static void translate_request(mizaru::pollrequest &request, pollfd &fd) {      assert( (fd.revents & pollhup) == 0);     assert( (fd.revents & pollerr) == 0);     assert( (fd.revents & pollnval) == 0);       switch(fd.revents)   {       case (pollin | pollout) :         request.reply = mizaru::poll_reply_rw;         break;       case pollin :         request.reply = mizaru::poll_reply_read;         break;       case pollout :         request.reply = mizaru::poll_reply_write;       default :         request.reply = 0;   }  }  /**  * @fills in fd.events based on request.request  * , fd.fd based on request.sock  */ static void prep_request(mizaru::pollrequest &request, pollfd &fd) {      fd.fd = request.sock.get_handle();     switch(request.request)   {      case mizaru::polltype::poll_read :       fd.events = pollin;       break;     case mizaru::polltype::poll_write :       fd.events = pollout;       break;     default :       fd.events = pollin | pollout;    }   }  void mizaru::trans::poll(mizaru::pollrequest &request,const std::chrono::milliseconds& wait_time) noexcept {    pollfd fd;   prep_request(request, fd);   poll(&fd, 1, wait_time.count());   translate_request(request, fd); } 

mizaru::pollrequest struct :

struct pollrequest {   pollrequest(polltype request, const syncsocket &sock) : sock(sock), request(request), reply(poll_reply_fail) {}   const syncsocket & sock;   polltype request;   uint8_t reply; }; 

syncsocket.get_handle() returns fd returned socket(int,int,int) in sys/socket.h

test function :

bool test_poll() {     mizaru::ipv4 ip ( "54.225.138.124" );     mizaru::syncsockettcp sock ( ip, 80 ,true);     mizaru::pollrequest  request{mizaru::polltype::poll_read, sock};     std::chrono::milliseconds time(1000);      mizaru::poll(request, time);      if(request.reply == mizaru::poll_reply_read)     {       std::cout << "fail test_poll first read" <<std::endl;        return false;     }       request.request = mizaru::polltype::poll_write;     mizaru::poll(request, time);      if(request.reply != mizaru::poll_reply_write)     {       std::cout << "fail test_poll first write" << std::endl;       return false;     }   std::string towrite ( "get / http/1.1\nhost: httpbin.org\n\n" );  mizaru::byte_buffer write_buff;  ( char c : towrite )     {       write_buff.push_back ( c );     }    unsigned int r_value = sock.write ( write_buff );     if (r_value != towrite.size())     {       std::cout << "fail test_poll r_value" << std::endl;       return false;    }        request.request = mizaru::polltype::poll_read;      mizaru::poll(request, time);      if(request.reply != mizaru::poll_reply_read)     {        std::cout << "fail test_poll second read" << std::endl;         return false;     }      request.request = mizaru::polltype::poll_write;      mizaru::poll(request, time);      if(request.reply != mizaru::poll_reply_write)     {       std::cout << "fail test_poll second write " << std::endl;         return false;     }      return true; } 

polltype enum :

enum polltype {poll_read, poll_write, poll_rw};

poll_reply_* constants :

constexpr uint8_t poll_reply_read = 0x01; constexpr uint8_t poll_reply_write = 0x02; constexpr uint8_t poll_reply_rw = poll_reply_read | poll_reply_write; constexpr uint8_t poll_reply_fail = 0; 

i sorry sample code not directly compilable trying make short, since proper http 200 ok reply can assume connecting , read/write handled properly. test fails when polling write

in translate_request():

switch(fd.revents) {   case (pollin | pollout) :     request.reply = mizaru::poll_reply_rw;   break;    case pollin :     request.reply = mizaru::poll_reply_read;   break;    case pollout :     request.reply = mizaru::poll_reply_write;   default :     request.reply = 0; } 

you missing break in both pollout , default cases. pollout falls through default, erasing evidence pollout occurred.