linux - socket::accept 继续返回 EGAIN

Question

我使用非阻塞套接字来接收新连接。但是代码多次未能 accept()。

int sockfd = ::socket(family, SOCK_STREAM | SOCK_NONBLOCK | SOCK_CLOEXEC, IPPROTO_TCP);
::bind(sockfd, bind_addr, static_cast<socklen_t>(sizeof(struct sockaddr_in6)));
ret = ::listen(sockfd, SOMAXCONN);

while (True) {
    ::poll(&*pollfds_.begin(), pollfds_.size(), timeoutMs);
    struct sockaddr_in6 addr;
    bzero(&addr, sizeof addr);
    socklen_t addrlen = static_cast<socklen_t>(sizeof *addr);
    int connfd = ::accept4(sockfd, sockaddr_cast(addr),
                         &addrlen, SOCK_NONBLOCK | SOCK_CLOEXEC);
}

errno 是 EAGAIN。

Answer 1

从联机帮助页到 accept(2):

EAGAIN or EWOULDBLOCK

The socket is marked nonblocking and no connections are present to be accepted. POSIX.1-2001 allows either error to be returned for this case, and does not require these constants to have the same value, so a portable application should check for both possibilities.

这意味着在客户端连接之前调用accept。