CODEWITHSUNDEEP
epoll
Dean Chen
Dean Chen

Reputation: 3890

How to send data immediately in epoll ET mode when connect established

My server needs to send data when client connects to it. I am using Epoll ET mode. But how to do it? Could any one give me a simple example for me?

Upvotes: 0

Views: 610

Answers (1)

Graham King
Graham King

Reputation: 5720

Assuming you are listening on your socket (socket, bind, listen), and have added it's descriptor to epoll (epoll_create and epoll_ctl), then epoll_wait will tell you when there is a new connection to accept.

First you accept the connection (sockfd is descriptor of socket you're listening on, efd is epoll instance) and add it to your epoll instance:

int connfd = accept4(sockfd, NULL, 0, SOCK_NONBLOCK);

struct epoll_event ev;
ev.events = EPOLLOUT | EPOLLET;
ev.data.fd = connfd;
epoll_ctl(efd, EPOLL_CTL_ADD, connfd, &ev)

Then you go back to your main loop and call epoll_wait again. It will tell you when the socket is ready for writing, and you just happily write or sendfile away.

Add lots of error checking, and probably TCP_CORK and you're done. There's a working example on github.com/grahamking/netshare/.

I hope this gives you enough information to get started.

Upvotes: 1

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