Will Epoll work with UDP listening socket for having a event driven UDP server

Question

I am trying to create a event driven multiple threads UDP/DTLS server. The design is based on the following concepts

1. Have a UDP socket where the Clients connects on
2. Use Epoll to ask for events on the UDP listen socket.

3. The UDP socket acts as a TCP listen socket and creates child fds that connect to the specific client. For this I have implemented a UDPAccept method for my object which has the pseudo code as shown below

   UDPAccept(int fd,struct sockaddr * addr,
      socklen_t * addr_len,void *sockBuf,size_t *read)
   {
       //sanity checks
       int childfd = -1;
       int error = 1;
       socklen_t localLen,peerLen;
       int family;
       struct sockaddr_in         local4,peer4;
       struct sockaddr            temp;
       size_t maxLen = 65535;
       getsockname(fd,(struct sockaddr *)&temp,&localLen);
       family = temp.sa_family;
       do
       {
        childfd = socket(family,SOCK_DGRAM,0);
        //error handling       
        //handle IPV6 
        local4 = (sockaddr_in *)temp;
        error = recvfrom( fd, sockBuf,
                           maxLen,0,(struct sockaddr *)&peer4,
                                            &peerLen);
        error = bind(childfd,(struct sockaddr *)&local4,sizeof local4);
        error = connect(childfd,(struct sockaddr *)&peerV4,peerLen);
       //handle error      
      }while(0);
      if(addr != NULL && addr_len != NULL)
      {
       *addr_len = peerLen;
       addr = &peerV4;
       *read = error;
      }    
      // error handling and cleanup
      return childfd;
   }
   

4. Add the child socket to Epoll table.

   epoll_ctl(efd,EPOLL_CTL_ADD,newFd,&event);
   

5. Poll for events on the child and listen socket

   currentSize = epoll_wait(efd,events,MAX_SOCKET_FD,timeout);
   //handle errors
   for(i = 0; i < currentSize;i++)
   {
   
       if(events[i].data.fd == listenUDP)
           //call UDPAccept
           // update local tables
      else
           //handle child fd events
   }
   

6. Have multiple threads to the same thing, synchronize using locks during accept

Now my question is will epoll stop giving me POLLIN events on the listening socket because I have created a new UDP child connected socket to the client or will I have to handle it myself

Answer 1

It will deliver events on both sockets unless you remove the first socket from events.

But I'm wondering why you're doing this. You can use a single UDP socket for everything. It's much simpler.