聊天室服务器程序

#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <assert.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>
#include <stdlib.h>
#include <sys/epoll.h>
#include <signal.h>
#include <sys/wait.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h>

#define USER_LIMIT 5
#define BUFFER_SIZE 1024
#define FD_LIMIT 65535
#define MAX_EVENT_NUMBER 1024
#define PROCESS_LIMIT 65536

/**
* 处理一个客户端连接必要的数据
*/
struct client_data {
sockaddr_in address;//客户端Socket地址
int connfd;//Socket文件描述符
pid_t pid;//处理这个连接的子进程的PID
int pipefd[2];//和父进程通信的管道
};

static const char* shm_name = "/my_shm";
int sig_pipefd[2];
int epollfd;
int listenfd;
int shmfd;
char* share_mem = 0;
//客户连接数组，进程用客户连接的编号来索引这个数组，即可取得相关的客户连接数据
client_data* users = 0;
//子进程和客户连接的映射关系表，用进程的PID来索引这个数组，即可取得该进程所处理的客户连接
int* sub_process = 0;
//当前客户数量
int user_count = 0;
bool stop_child = false;

int setnonblocking(int fd) {
int old_option = fcntl(fd, F_GETFL);
int new_option = old_option | O_NONBLOCK;
fcntl(fd, F_SETFL, new_option);
return old_option;
}

void addfd(int epollfd, int fd) {
epoll_event event;
event.data.fd = fd;
event.events = EPOLLIN | EPOLLET;
epoll_ctl(epollfd, EPOLL_CTL_ADD, fd, &event);
setnonblocking(fd);
}

void sig_handler(int sig) {
int save_errno = errno;
int msg = sig;
send(sig_pipefd[1], (char*) &msg, 1, 0);
errno = save_errno;
}

void addsig(int sig, void(*handler)(int), bool restart = true) {
struct sigaction sa;
memset(&sa, '\0', sizeof(sa));
sa.sa_handler = handler;
if (restart) {
sa.sa_flags |= SA_RESTART;
}
sigfillset(&sa.sa_mask);
assert( sigaction( sig, &sa, NULL ) != -1 );
}

void del_resource() {
close(sig_pipefd[0]);
close(sig_pipefd[1]);
close(listenfd);
close(epollfd);
shm_unlink(shm_name);
delete[] users;
delete[] sub_process;
}

//停止一个子进程
void child_term_handler(int sig) {
stop_child = true;
}

/**
* 子进程运行的函数。参数idx指出该子进程处理的客户连接的编号，users时保存所有客户连接
* 数据的数组，参数share_mem指出共享内存的起始地址
*/
int run_child(int idx, client_data* users, char* share_mem) {
epoll_event events[MAX_EVENT_NUMBER];
/*
* 子进程使用I/O复用技术来同时监听两个文件描述符，客户端连接Socket，与父进程通信的管道文件
* 描述符
*/
int child_epollfd = epoll_create(5);
assert( child_epollfd != -1 );
int connfd = users[idx].connfd;
addfd(child_epollfd, connfd);
int pipefd = users[idx].pipefd[1];
addfd(child_epollfd, pipefd);
int ret;
//子进程需要设置自己的信号处理函数
addsig(SIGTERM, child_term_handler, false);

while (!stop_child) {
int number = epoll_wait(child_epollfd, events, MAX_EVENT_NUMBER, -1);
if ((number < 0) && (errno != EINTR)) {
printf("epoll failure\n");
break;
}

for (int i = 0; i < number; i++) {
int sockfd = events[i].data.fd;
//本子进程负责的客户连接有数据到达
if ((sockfd == connfd) && (events[i].events & EPOLLIN)) {
memset(share_mem + idx * BUFFER_SIZE, '\0', BUFFER_SIZE);
/**
*
将客户数据读取到对应的数据缓存中，该读缓存时共享内存的一段，它开始于idx*BUFFER_SIZE
处，长度为BUFFER_SIZE字节，因此，各个客户连接的读缓存时共享的*/
ret = recv(connfd, share_mem + idx * BUFFER_SIZE,
BUFFER_SIZE - 1, 0);
if (ret < 0) {
if (errno != EAGAIN) {
stop_child = true;
}
} else if (ret == 0) {
stop_child = true;
} else {
//成功读取客户数据后就通知主进程（通过管道）来处理
send(pipefd, (char*) &idx, sizeof(idx), 0);
}
//主进程通知本进程（通过管道）将第client个客户的数据发送到本进程负责的客户端
} else if ((sockfd == pipefd) && (events[i].events & EPOLLIN)) {
int client = 0;
//接收主进程发送来的数据，即有客户数据到达的连接的编号
ret = recv(sockfd, (char*) &client, sizeof(client), 0);
if (ret < 0) {
if (errno != EAGAIN) {
stop_child = true;
}
} else if (ret == 0) {
stop_child = true;
} else {
send(connfd, share_mem + client * BUFFER_SIZE, BUFFER_SIZE,
0);
}
} else {
continue;
}
}
}

close(connfd);
close(pipefd);
close(child_epollfd);
return 0;
}

int main(int argc, char* argv[]) {
if (argc <= 2) {
printf("usage: %s ip_address port_number\n", basename(argv[0]));
return 1;
}
const char* ip = argv[1];
int port = atoi(argv[2]);

int ret = 0;
struct sockaddr_in address;
bzero(&address, sizeof(address));
address.sin_family = AF_INET;
inet_pton(AF_INET, ip, &address.sin_addr);
address.sin_port = htons(port);

listenfd = socket(PF_INET, SOCK_STREAM, 0);
assert( listenfd >= 0 );

ret = bind(listenfd, (struct sockaddr*) &address, sizeof(address));
assert( ret != -1 );

ret = listen(listenfd, 5);
assert( ret != -1 );

user_count = 0;
users = new client_data[USER_LIMIT + 1];
sub_process = new int[PROCESS_LIMIT];
for (int i = 0; i < PROCESS_LIMIT; ++i) {
sub_process[i] = -1;
}

epoll_event events[MAX_EVENT_NUMBER];
epollfd = epoll_create(5);
assert( epollfd != -1 );
addfd(epollfd, listenfd);

ret = socketpair(PF_UNIX, SOCK_STREAM, 0, sig_pipefd);
assert( ret != -1 );
setnonblocking(sig_pipefd[1]);
addfd(epollfd, sig_pipefd[0]);

addsig(SIGCHLD, sig_handler);
addsig(SIGTERM, sig_handler);
addsig(SIGINT, sig_handler);
addsig(SIGPIPE, SIG_IGN);
bool stop_server = false;
bool terminate = false;

//创建共享内存，作为所有客户socket连接的读缓存
shmfd = shm_open(shm_name, O_CREAT | O_RDWR, 0666);
assert( shmfd != -1 );
ret = ftruncate(shmfd, USER_LIMIT * BUFFER_SIZE);
assert( ret != -1 );

share_mem = (char*) mmap(NULL, USER_LIMIT * BUFFER_SIZE,
PROT_READ | PROT_WRITE, MAP_SHARED, shmfd, 0);
assert( share_mem != MAP_FAILED );
close(shmfd);

while (!stop_server) {
int number = epoll_wait(epollfd, events, MAX_EVENT_NUMBER, -1);
if ((number < 0) && (errno != EINTR)) {
printf("epoll failure\n");
break;
}

for (int i = 0; i < number; i++) {
int sockfd = events[i].data.fd;
//新的客户连接到来
if (sockfd == listenfd) {
struct sockaddr_in client_address;
socklen_t client_addrlength = sizeof(client_address);
int connfd = accept(listenfd,
(struct sockaddr*) &client_address, &client_addrlength);
if (connfd < 0) {
printf("errno is: %d\n", errno);
continue;
}
if (user_count >= USER_LIMIT) {
const char* info = "too many users\n";
printf("%s", info);
send(connfd, info, strlen(info), 0);
close(connfd);
continue;
}
//保存第user_count个客户连接的相关数据
users[user_count].address = client_address;
users[user_count].connfd = connfd;
//在主进程和子进程间建立管道，以传递必要的数据
ret = socketpair(PF_UNIX, SOCK_STREAM, 0,
users[user_count].pipefd);
assert( ret != -1 );
pid_t pid = fork();
if (pid < 0) {
close(connfd);
continue;
} else if (pid == 0) {
close(epollfd);
close(listenfd);
close(users[user_count].pipefd[0]);
close(sig_pipefd[0]);
close(sig_pipefd[1]);
run_child(user_count, users, share_mem);
munmap((void*) share_mem, USER_LIMIT * BUFFER_SIZE);
exit(0);
} else {
close(connfd);
close(users[user_count].pipefd[1]);
addfd(epollfd, users[user_count].pipefd[0]);
users[user_count].pid = pid;
//记录新的客户连接在数组users中的索引值，建立进程PID和该索引值之间的映射关系
sub_process[pid] = user_count;
user_count++;
}
//处理信号事件
} else if ((sockfd == sig_pipefd[0])
&& (events[i].events & EPOLLIN)) {
int sig;
char signals[1024];
ret = recv(sig_pipefd[0], signals, sizeof(signals), 0);
if (ret == -1) {
continue;
} else if (ret == 0) {
continue;
} else {
for (int i = 0; i < ret; ++i) {
switch (signals[i]) {
//子进程退出，表示有某个客户端关闭了连接
case SIGCHLD: {
pid_t pid;
int stat;
while ((pid = waitpid(-1, &stat, WNOHANG)) > 0) {
//用子进程的PID取得被关闭的客户连接的编号
int del_user = sub_process[pid];
sub_process[pid] = -1;
if ((del_user < 0) || (del_user > USER_LIMIT)) {
printf("the deleted user was not change\n");
continue;
}
//清除第del_user个客户连接使用的相关数据
epoll_ctl(epollfd, EPOLL_CTL_DEL,
users[del_user].pipefd[0], 0);
close(users[del_user].pipefd[0]);
users[del_user] = users[--user_count];
sub_process[users[del_user].pid] = del_user;
printf("child %d exit, now we have %d users\n",
del_user, user_count);
}
if (terminate && user_count == 0) {
stop_server = true;
}
break;
}
case SIGTERM:
//结束服务器程序
case SIGINT: {
printf("kill all the clild now\n");
//addsig( SIGTERM, SIG_IGN );
//addsig( SIGINT, SIG_IGN );
if (user_count == 0) {
stop_server = true;
break;
}
for (int i = 0; i < user_count; ++i) {
int pid = users[i].pid;
kill(pid, SIGTERM);
}
terminate = true;
break;
}
default: {
break;
}
}
}
}
//某个子进程向父进程写入了数据
} else if (events[i].events & EPOLLIN) {
int child = 0;
//读取管道数据，child变量记录了是哪个客户连接有数据到达
ret = recv(sockfd, (char*) &child, sizeof(child), 0);
printf("read data from child accross pipe\n");
if (ret == -1) {
continue;
} else if (ret == 0) {
continue;
} else {
//向除负责处理第child个客户连接的子进程之外的其他子进程发送消息，通知它们有客户数据要写
for (int j = 0; j < user_count; ++j) {
if (users[j].pipefd[0] != sockfd) {
printf("send data to child accross pipe\n");
send(users[j].pipefd[0], (char*) &child,
sizeof(child), 0);
}
}
}
}
}
}

del_resource();
return 0;
}