Linux 网络编程 epoll 文件描述符

[乳酸奶]

服务器端新建一个监听套接字时，文件描述符是3；当客户端连接服务器时，新建一个连接套接字，该文件描述符应该是4才对吧？但实际输出是5，为什么呢？求助大神！

服务器代码（图片）：


客户端代码（图片）：


服务器代码：

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>          
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <sys/epoll.h>

int init_server(const char *ipstr, unsigned short port, int backlog)
{
	int s = socket(PF_INET, SOCK_STREAM, 0);
	if(0 > s){
		perror("socket");
		return -1;
	}
	printf("s = %d\n", s);
	struct sockaddr_in addr = {
		.sin_family = PF_INET,
		.sin_port   = htons(port),
		.sin_addr   = {
			.s_addr = ((ipstr == NULL) ? INADDR_ANY : inet_addr(ipstr)),
		},
	};
	memset(addr.sin_zero, 0, sizeof(addr.sin_zero));
	socklen_t len = sizeof(addr);
	if(0 > bind(s, (struct sockaddr*)&addr, len)){
		perror("bind");
		return -1;
	}
	
	if(0 > listen(s, backlog)){
		perror("listen");
		return -1;
	}

	return s;	
}

int add_event(int efd, int fd, unsigned int event)
{
	struct epoll_event evt;
	evt.events = event;
	evt.data.fd = fd;
	return epoll_ctl(efd, EPOLL_CTL_ADD, fd, &evt);
}

int del_event(int efd, int fd, unsigned int event)
{
	struct epoll_event evt = {
		.events = event,
		.data = {
			.fd = fd,
		},
	};
	return epoll_ctl(efd, EPOLL_CTL_DEL, fd, &evt);
}

int main()
{
	int s = init_server(NULL, 9999, 3);
	if(0 > s){
		return -1;
	}

	int efd = epoll_create(1);
	if(0 > efd){
		perror("epoll_create");
		return -1;
	}

	if(0 > add_event(efd, s, EPOLLIN)){
		perror("add_event");
		return -1;
	}

	printf("Wait for a new comming ...\n");

	#define MAX 1024
	struct epoll_event evts[MAX];
	int timeout = -1;
	while(1){
		int ret = epoll_wait(efd, evts, MAX, timeout);
		if(0 > ret){
			perror("epoll_wait");
			break;
		}else if(0 == ret){
			printf("\tTimeout.\n");
			continue;
		}
		int i;
		for(i = 0; i < ret; i++){
			if(s == evts[i].data.fd){
				struct sockaddr_in addr;
				memset(&addr, 0, sizeof(addr));
				socklen_t len = sizeof(addr);
				
				int rws = accept(s, (struct sockaddr*)&addr, &len);
				if(0 > rws){
					perror("accept");
					close(s);
					return -1;
				}

				printf("client %d :ip[%s]:port[%u]\n", 
						rws, inet_ntoa(addr.sin_addr), ntohs(addr.sin_port));

				if(0 > add_event(efd, rws, EPOLLIN)){
					perror("add_event fail ");
					close(rws);
				}
			}else{
				char buf[MAX];
				memset(buf, 0, MAX);
				int num = recv(evts[i].data.fd, buf, MAX-1, 0);
				if(0 >= num){
					printf("id = %d, client %d leave.\n", i, evts[i].data.fd);
					if(0 > del_event(efd, evts[i].data.fd, EPOLLIN))
						perror("del fd");
					close(evts[i].data.fd);
				}else{
					printf("socket[%d], RECV[%dbytes]:%s\n", 
						evts[i].data.fd, num, buf);
				}
			}
		}
	}
}

客户端代码：

#include <stdio.h>
#include <string.h>
#include <sys/types.h>          
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>


int main(int argc, char *argv[])
{
	char *ipstr = "127.0.0.1";
	unsigned short port = 9999;
	if(argc == 3){
		ipstr = argv[1];
		port = atoi(argv[2]);
	}

	int c = socket(PF_INET, SOCK_STREAM,0);
	if (c < 0){
		perror("socket");
		return -1;
	}
	struct sockaddr_in addr = {
		.sin_family = PF_INET,
		.sin_port = htons(port),
		.sin_addr.s_addr = inet_addr(ipstr),
		.sin_zero = {0},
	};
	if(connect(c, (struct sockaddr *)&addr, 
		sizeof(addr)) < 0){
		perror("connect");
		return -1;
	}
	int id = 0;
	#define MAX 1024
	char buf[MAX];
	int size;
	while(1){
		snprintf(buf, MAX, "NO.%d: hello world", id++);
		size = strlen(buf);
		if (0 >= send(c, buf, size, 0)){
			printf("Send fail!\n");
			break;
		}

		printf("send: [%dbytes]: %s\n", size, buf);
		sleep(1);
	}
	close(c);
	return 0;
}

测试结果：

[JiangWenjie2014]

stdin:0 stdout:1 stderr:2 listenfd:3 epollfd:4 clientfd:5

[乳酸奶]

感谢大神，完美简洁解决我的问题了！