完整教程：嵌入式第四十天(TCP并发服务端(IO多路复用))

一.IO多路复用:

1.select

2.poll

3.epoll

二.epoll

1.
epoll 会维护一个红黑树结构，专门用于存储用户注册的、需要监控其 IO 事件的文件描述符。红黑树的特性（有序、查找/插入/删除效率高，时间复杂度为 O(log n)）保证了 epoll 能高效管理大量的文件描述符，即使监控的 FD 数量庞大，相关操作也能保持较好的性能。

此外，epoll 还会维护一个就绪链表，当监控的 FD 有 IO 事件触发时（如可读、可写），对应的 FD 会被放入该链表中。用户调用  epoll_wait  时，只需直接从就绪链表中获取就绪的 FD 即可，无需遍历所有注册的 FD，这也是 epoll 相比 select/poll 高效的关键原因之一。

总结来说：epoll 通过红黑树存储所有注册的待监控 FD，通过就绪链表存储已触发 IO 事件的 FD，两者配合实现了高效的 IO 多路复用管理。

2.

3.

#ifndef _HEAD_H
#define _HEAD_H
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include  /* superset of previous */
#include
#include
#include
#include
#include
#include
#include
#endif

#include "head.h"
#define MAX_FD_CNT 100
int epoll_fd_add(int epfds, int fd, uint32_t events)
{
struct epoll_event ev;
ev.events = events;
ev.data.fd = fd;
int ret = epoll_ctl(epfds, EPOLL_CTL_ADD, fd, &ev);
if (ret ok");
cnt = send(evs[i].data.fd,buff,strlen(buff),0);
if(cnt < 0)
{
perror("send error");
epoll_del_fd(epfds,evs[i].data.fd);
close(evs[i].data.fd);
continue;
}
}
}
}
close(sockfd);
return 0;
}

4.

#include"head.h"
#define SER_PORT  50000
#define SER_IP    "192.168.19.129"
#define MAX_FD_CNT 256
int connfds_g[MAX_FD_CNT] = {0};
int total_fd_g = 0;
int save_connfd(int *connfds_g, int fd)
{
if (total_fd_g >= MAX_FD_CNT || total_fd_g = total_fd_g)
{
printf("connfds_g Not found %d\n", fd);
return -1;
}
for ( ;i < total_fd_g-1; ++i)
{
connfds_g[i] = connfds_g[i+1];
}
total_fd_g--;
if (total_fd_g < 0)
{
return -1;
}
return 0;
}
int init_tcp_ser()
{
int sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
{
perror("socket error");
return -1;
}
struct sockaddr_in seraddr;
seraddr.sin_family = AF_INET;
seraddr.sin_port = htons(SER_PORT);
seraddr.sin_addr.s_addr = inet_addr(SER_IP);
int ret = bind(sockfd, (struct sockaddr *)&seraddr, sizeof(seraddr));
if (ret < 0)
{
perror("bind error");
return -1;
}
ret = listen(sockfd, 100);
if (ret < 0)
{
perror("listen error");
return -1;
}
return sockfd;
}
int epoll_add_fd(int epfds, int fd, uint32_t events)
{
struct epoll_event ev;
ev.events = events;
ev.data.fd = fd;
int ret = epoll_ctl(epfds, EPOLL_CTL_ADD, fd, &ev);
if (ret < 0)
{
perror("epoll_ctl add error");
return -1;
}
return 0;
}
int epoll_del_fd(int epfds, int fd)
{
int ret = epoll_ctl(epfds, EPOLL_CTL_DEL, fd, NULL);
if (ret < 0)
{
perror("epoll_ctl del error");
return -1;
}
return 0;
}
int main(int argc, const char *argv[])
{
Msg_t mymsg;
struct sockaddr_in cliaddr;
socklen_t clilen = sizeof(cliaddr);
int sockfd = init_tcp_ser();
if (sockfd < 0)
{
return -1;
}
int epfds = epoll_create(MAX_FD_CNT);
if (epfds < 0)
{
perror("epoll_create error");
return -1;
}
epoll_add_fd(epfds, sockfd, EPOLLIN);
struct epoll_event evs[MAX_FD_CNT];
while (1)
{
int cnt = epoll_wait(epfds, evs, MAX_FD_CNT, -1);
if (cnt < 0)
{
perror("epoll_wait error");
return -1;
}
for (int i = 0; i < cnt; ++i)
{
if (sockfd == evs[i].data.fd)
{
int connfd = accept(sockfd, (struct sockaddr *)&cliaddr, &clilen);
if (connfd < 0)
{
perror("accept error");
return -1;
}
epoll_add_fd(epfds, connfd, EPOLLIN);
save_connfd(connfds_g, connfd);
}
else
{
memset(&mymsg, 0, sizeof(mymsg));
ssize_t size = recv(evs[i].data.fd, &mymsg, sizeof(Msg_t), 0);
if (size < 0)
{
perror("recv error");
epoll_del_fd(epfds, evs[i].data.fd);
close(evs[i].data.fd);
continue;
}
else if (0 == size)
{
epoll_del_fd(epfds, evs[i].data.fd);
close(evs[i].data.fd);
continue;
}
if (mymsg.type == MSG_JOIN)
{
printf("[%s] 加入群聊!\n", mymsg.name);
}
else if (mymsg.type == MSG_QUIT)
{
printf("[%s] 退出群聊!\n", mymsg.name);
}
else if(mymsg.type == MSG_CHAT)
{
printf("[%s]:%s\n",mymsg.name,mymsg.buff);
}
for (int j = 0; j < total_fd_g; ++j)
{
if (evs[i].data.fd != connfds_g[j])
{
size = send(connfds_g[j], &mymsg, sizeof(Msg_t), 0);
if (size < 0)
{
perror("send error");
close(connfds_g[j]);
del_connfd(connfds_g, connfds_g[j]);
continue;
}
}
}
}
}
}
close(sockfd);
return 0;
}

#include "head.h"
#define SER_PORT  50000
#define SER_IP    "192.168.19.129"
int sockfd;
char username[64] = {0};
void *recv_thread(void *arg)
{
Msg_t mymsg;
while(1)
{
memset(&mymsg, 0, sizeof(mymsg));
ssize_t size = recv(sockfd, &mymsg, sizeof(Msg_t), 0);
if(size \n", argv[0]);
return -1;
}
strncpy(username, argv[1], sizeof(username)-1);
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if(sockfd < 0)
{
perror("socket error");
return -1;
}
struct sockaddr_in seraddr;
seraddr.sin_family = AF_INET;
seraddr.sin_port = htons(SER_PORT);
seraddr.sin_addr.s_addr = inet_addr(SER_IP);
int connfd = connect(sockfd, (struct sockaddr*)&seraddr, sizeof(seraddr));
if(connfd < 0)
{
perror("connect error");
close(sockfd);
return -1;
}
Msg_t join_msg;
join_msg.type = MSG_JOIN;
strncpy(join_msg.name, username, sizeof(join_msg.name)-1);
strncpy(join_msg.buff, "Hello I'm zhangsan", sizeof(join_msg.buff)-1);
int cnt = send(sockfd, &join_msg, sizeof(Msg_t), 0);
if(cnt < 0)
{
perror("send join msg error");
close(sockfd);
return -1;
}
pthread_t tid;
pthread_create(&tid, NULL, recv_thread, NULL);
Msg_t send_msg;
send_msg.type = MSG_CHAT;
strncpy(send_msg.name, username, sizeof(send_msg.name)-1);
printf("进入群聊!输入'quiet'退出\n");
while(1)
{
fgets(send_msg.buff, sizeof(send_msg.buff), stdin);
send_msg.buff[strlen(send_msg.buff) - 1] = '\0';
if(strcmp(send_msg.buff, "quiet") == 0)
{
printf("退出聊天\n");
break;
}
int cnt = send(sockfd, &send_msg, sizeof(Msg_t), 0);
if(cnt < 0)
{
perror("send msg error");
break;
}
}
Msg_t quit_msg;
quit_msg.type = MSG_QUIT;
strncpy(quit_msg.name, username, sizeof(quit_msg.name)-1);
strncpy(quit_msg.buff, "zhangsan go go go!", sizeof(quit_msg.buff)-1);
send(sockfd, &quit_msg, sizeof(Msg_t), 0);
close(sockfd);
return 0;
}