linux c 使用epoll处理socket连接以及客户端读写入门

#include <sys/wait.h>
#include <stdint.h>
#include <sys/types.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <signal.h>
#include <time.h>
#include <string.h>
#include <sys/times.h>
#include <sys/epoll.h>
#include <fcntl.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <netinet/in.h>

/**
 * https://man7.org/linux/man-pages/man7/epoll.7.html

 The following system calls are provided to create and manage an
 epoll instance:

 • epoll_create(2) creates a new epoll instance and returns a file
 descriptor referring to that instance.  (The more recent
 epoll_create1(2) extends the functionality of epoll_create(2).)

 • Interest in particular file descriptors is then registered via
 epoll_ctl(2), which adds items to the interest list of the
 epoll instance.

 • epoll_wait(2) waits for I/O events, blocking the calling thread
 if no events are currently available.  (This system call can be
 thought of as fetching items from the ready list of the epoll
 instance.)

 */

#define MAX_EVENTS 10

int setnonblocking(int fd) {
	int flags;

	if (-1 == (flags = fcntl(fd, F_GETFL, 0)))
		flags = 0;
	return fcntl(fd, F_SETFL, flags | O_NONBLOCK);
}

void do_use_fd(int fd, char *buffer) {
	printf("do_use_fd n");
	while (1) {
		int length = read(fd, buffer, 1023);
		if (length <= 0) {
			printf("read error n");
			perror("read error");
			break;
		}
		buffer[length] = '';
		printf("%s", buffer);
		write(fd, buffer, length);
	}
}

int main() {
	char buffer[1024] = { 0 };
	int listenfd = 0;
	int conn_sock = 0;
	struct sockaddr_in address;
	int addrlen = sizeof(address);
	listenfd = socket(AF_INET, SOCK_STREAM, 0);
	memset(&address, '0', addrlen);

	address.sin_family = AF_INET;
	address.sin_addr.s_addr = htonl(INADDR_ANY);
	address.sin_port = htons(8080);

	bind(listenfd, (struct sockaddr*) &address, addrlen);

	if (listen(listenfd, 3) < 0) {
		perror("listen");
		exit(EXIT_FAILURE);
	}

	int epollfd;
	struct epoll_event ev;
	struct epoll_event events[MAX_EVENTS];
	int nfds;
	epollfd = epoll_create1(0);
	if (epollfd == -1) {
		perror("epoll_create1");
		exit(EXIT_FAILURE);
	}

	ev.events = EPOLLIN;
	ev.data.fd = listenfd;

	if (epoll_ctl(epollfd, EPOLL_CTL_ADD, listenfd, &ev) == -1) {
		perror("epoll_ctl: listen_sock");
		exit(EXIT_FAILURE);
	}

	for (;;) {
		printf("epoll_wait n");
		nfds = epoll_wait(epollfd, events, MAX_EVENTS, -1);
		if (nfds == -1) {
			perror("epoll_wait");
			exit(EXIT_FAILURE);
		}
		printf("new msg n");
		for (int n = 0; n < nfds; n++) {
			if (events[n].data.fd == listenfd) {
				conn_sock = accept(listenfd, (struct sockaddr*) &address,
						(socklen_t*) &addrlen);
				if (conn_sock < 0) {
					perror("accept");
					exit(EXIT_FAILURE);
				}
				setnonblocking(conn_sock);
				ev.events = EPOLLIN | EPOLLET;
				ev.data.fd = conn_sock;
				if (epoll_ctl(epollfd, EPOLL_CTL_ADD, conn_sock, &ev) == -1) {
					perror("epoll_ctl: conn_sock");
					exit(EXIT_FAILURE);
				}
			} else {
				do_use_fd(events[n].data.fd, buffer);
			}
		}
	}
	shutdown(listenfd, SHUT_RDWR);
	return EXIT_SUCCESS;
}

测试 ： telnet 127.0.0.1 8080
可以打开2个终端来测试。

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