参考：linux高性能服务器编程，作者：游双
程序简介：该程序用了共享内存来实现进程间的同步，由于只是同时读取共享内存，所以没有用到锁。该程序的功能是服务器监听网络连接，当有一个客户端连接时，服务器创建一个子进程处理该连接。每个子进程只负责自己的客户端以及和父进程通信。当子进程从客户端读取数据后，把数据放到共享内存上，每个子进程在共享内存上有自己的一段空间，因此不会出现同时写。放上去后通知父进程，说：共享内存上有新数据到达了，然后父进程通知其他子进程，去到该位置读取数据，把数据发送到自己的客户端，实现了群聊的效果。该程序对于多进程编程的初学者是个不错的例子，写下来是为了让自己熟悉一下。
服务器代码：编译的时候需要加上 -lrt选项
#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的必要数据 */
struct client_data
{
sockaddr_in address;
int connfd; /* 客户端的fd */
pid_t pid; /* 处理这个连接的子进程的pid */
int pipefd[2]; /* 和父进程通信用的管道 */
};
int sig_pipefd[2];//当有信号发生时，用于父进程自己的通信
char* share_mem;
int user_count = 0; //当前客户的数量
client_data* users = 0 ;
int* sub_process = 0;
static const char* shm_name = "/my_share_memory";
int maxevents = 100;
bool stop_child = false;
void setnonblock(int fd)
{
int flag = fcntl(fd,F_GETFL);
assert(flag != -1);
fcntl(fd,F_SETFL,flag | O_NONBLOCK);
}
void addfd(int epollfd,int fd)
{
epoll_event ee;
ee.data.fd = fd;
ee.events = EPOLLIN | EPOLLET;
epoll_ctl(epollfd,EPOLL_CTL_ADD,fd,&ee);
setnonblock(fd);
}
void sig_handler(int sig)
{
int save_errno = errno;
int msg = sig;
send(sig_pipefd[1],(char*)&msg,1,0);
errno = save_errno;//恢复错误值
}
void child_sig_handler(int sig)
{
stop_child = true;
}
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);//作用?
assert(sigaction(sig,&sa,NULL) != -1);
}
/* 子进程的处理函数，idx表示该子进程处理的客户端连接的编号，users表示所有客户端连接数据的数组，share_mem表示共享内存的起始地址 */
int run_child(int idx,client_data* users,char* share_mem)
{
int connfd = users[idx].connfd;
int pipefd = users[idx].pipefd[1];
int epollfd = epoll_create(100);//子进程的事件处理函数
assert(epollfd != -1);
addfd(epollfd,connfd);//与客户端通信
addfd(epollfd,pipefd);//与父进程通信
addsig(SIGTERM,child_sig_handler,false);
epoll_event events[maxevents];
int ret;
while(!stop_child)
{
int number = epoll_wait(epollfd,events,maxevents,-1);
if(number < 0 && errno != EINTR)
{
printf("epoll error\n");
break;
}
int i;
for(i = 0;i < number;i++)
{
int sockfd = events[i].data.fd;
if(sockfd == connfd && (events[i].events & EPOLLIN))//客户端发来数据
{
memset(share_mem+idx*BUFFER_SIZE,'\0',BUFFER_SIZE);
/* 将客户端数据读取到对应的读缓存中，该读缓存是共享内存的一段 */
ret = recv(sockfd,share_mem+idx*BUFFER_SIZE,BUFFER_SIZE-1,0);
if(ret < 0 && errno != EAGAIN)
{
printf("recv error\n");
stop_child = true;
}
else if(ret == 0)
{
printf("client close\n");
stop_child = true;
}
else
{
send(pipefd,(char*)&idx,sizeof(idx),0);//告诉父进程，“我”收到数据了
}
}
/* 父进程通知"我"将第client个客户端的数据发送到我负责的客户端 */
else if(sockfd == pipefd && (events[i].events & EPOLLIN))
{
int client = 0;
ret = recv(sockfd,(char*)&client,sizeof(client),0);
if(ret < 0 && errno != EAGAIN)stop_child = true;
else if(ret == 0) stop_child = true;
else
{
send(connfd,share_mem+client*BUFFER_SIZE,BUFFER_SIZE,0);
}
}
}
}
close(connfd);
close(pipefd);
close(epollfd);
return 0;
}
int main(int argc,char* argv[])
{
if(argc != 3)
{
printf("usage %s server_ip server_port \n",basename(argv[0]));
return -1;
}
sockaddr_in server;
server.sin_family = AF_INET;
inet_pton(AF_INET,argv[1],&server.sin_addr);
server.sin_port = htons(atoi(argv[2]));
int listenfd = socket(AF_INET,SOCK_STREAM,0);
assert(listenfd != -1);
int opt = 1;
int ret = setsockopt(listenfd,SOL_SOCKET,SO_REUSEADDR,&opt,sizeof(opt));
assert(ret == 0);
ret = bind(listenfd,(const sockaddr*)&server,sizeof(server));
assert(ret != -1);
ret = listen(listenfd,100);
assert(ret != -1);
/* 初始化连接池 */
user_count = 0;
users = new client_data[USER_LIMIT+1];
sub_process = new int[PROCESS_LIMIT];
int i;
for(i = 0; i < PROCESS_LIMIT;++i)
{
sub_process[i] = -1;
}
/* epoll的初始化 */
int epollfd = epoll_create(100);
assert(epollfd != -1);
addfd(epollfd,listenfd);//监听网络连接端口
ret = socketpair(AF_UNIX,SOCK_STREAM,0,sig_pipefd);//当有信号发生时，用于父进程自己的通信
assert(ret != -1);
setnonblock(sig_pipefd[1]);//UNIX域套接字的0号端口用于信号处理函数
addfd(epollfd,sig_pipefd[0]);//主进程监听UNIX域套接字的1号端口
/* 设置信号处理函数 */
addsig(SIGCHLD,sig_handler);
addsig(SIGPIPE,SIG_IGN);
addsig(SIGINT,sig_handler);
addsig(SIGTERM,sig_handler);
/* 创建共享内存，用于所有客户socket连接的读缓存 */
int shmfd = shm_open(shm_name,O_CREAT|O_RDWR,0666);
assert(shmfd != -1);
ret = ftruncate(shmfd,USER_LIMIT*BUFFER_SIZE);//设置shmfd的大小
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);
/* 进入epoll事件循环 */
bool stop_server = false;
bool terminate = false;
epoll_event events[maxevents];
while(!stop_server)
{
int number = epoll_wait(epollfd,events,maxevents,-1);
if(number < 0 && errno != EINTR)
{
printf("epoll error\n");
break;
}
for(i = 0;i < number;i++)
{
int sockfd = events[i].data.fd;
/* 新的客户连接 */
if(sockfd == listenfd)
{
sockaddr_in client;
socklen_t clilen = sizeof(client);
int connfd = accept(listenfd,(struct sockaddr*)&client,&clilen);
if(connfd < 0)
{
printf("accept error\n");
continue;
}
if(user_count >= USER_LIMIT)
{
const char* info = "to many users\n";
printf("%s\n",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;
users[user_count].connfd = connfd;
ret = socketpair(AF_UNIX,SOCK_STREAM,0,users[user_count].pipefd);
assert( ret != -1);
pid_t pid = fork();
if(pid < 0)
{
close(connfd);
continue;
}
if(pid == 0)//子进程
{
close(sig_pipefd[0]);
close(sig_pipefd[1]);
close(users[user_count].pipefd[0]);//子进程关闭0端口
close(listenfd);
close(epollfd);
run_child(user_count,users,share_mem);//子进程的处理函数
munmap((void*)share_mem,USER_LIMIT*BUFFER_SIZE);
exit(0);
}
else //父进程
{
close(users[user_count].pipefd[1]);//父进程关闭1端口
close(connfd);
addfd(epollfd,users[user_count].pipefd[0]);
users[user_count].pid = pid;
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(sockfd,signals,sizeof(signals),0);
if(ret < 0 && ret != EAGAIN)
{
printf("recv error\n");
continue;
}
if(ret == 0)continue;
for(i = 0; i < ret; ++ i)
{
switch(signals[i])
{
case SIGCHLD : //子进程关闭
{
pid_t pid;
int status;
while((pid = waitpid(-1,&status,WNOHANG)) > 0)
{
/* 用子进程的pid获取被关闭的客户端连接的编号 */
int del_user = sub_process[pid];
sub_process[del_user] = -1;
/* 清楚第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]);
/* 把最后一个客户连接的信息移动到该位置，用于保证0~user_count-1直接的连接都是活着的 */
users[del_user] = users[--user_count];
sub_process[users[del_user].pid] = del_user;
}
if(terminate && user_count == 0) stop_server = true;
break;
}
case SIGINT :
case SIGTERM : //结束服务器进程
{
printf("kill all the child now\n");
for(i = 0 ;i < user_count;++i)
{
pid_t pid = users[i].pid;
kill(pid,SIGTERM);
}
terminate = true;//此处不是stop_sever是为了等待所有子进程结束后再结束
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;
ret = recv(sockfd,(char*)&child,sizeof(child),0);
if(ret < 0 && errno != EAGAIN) continue;
else if(ret == 0)continue;
printf("read data from child accross pipe\n");
for(i = 0 ;i < user_count;i++)
{
if(i != child)
{
printf("send data to child accross pipe\n");
send(users[i].pipefd[0],(char*)&child,sizeof(child),0);
}
}
}
}
}
close(listenfd);
close(epollfd);
close(sig_pipefd[0]);
close(sig_pipefd[1]);
shm_unlink(shm_name);
delete[] users;
delete[] sub_process;
return 0;
}
#define _GNU_SOURCE 1
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <assert.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <poll.h>
#include <fcntl.h>
#define BUFFER_SIZE 64
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] );
struct sockaddr_in server_address;
bzero( &server_address, sizeof( server_address ) );
server_address.sin_family = AF_INET;
inet_pton( AF_INET, ip, &server_address.sin_addr );
server_address.sin_port = htons( port );
int sockfd = socket( PF_INET, SOCK_STREAM, 0 );
assert( sockfd >= 0 );
if ( connect( sockfd, ( struct sockaddr* )&server_address, sizeof( server_address ) ) < 0 )
{
printf( "connection failed\n" );
close( sockfd );
return 1;
}
pollfd fds[2];
fds[0].fd = 0;
fds[0].events = POLLIN;
fds[0].revents = 0;
fds[1].fd = sockfd;
fds[1].events = POLLIN | POLLRDHUP;
fds[1].revents = 0;
char read_buf[BUFFER_SIZE];
int pipefd[2];
int ret = pipe( pipefd );
assert( ret != -1 );
while( 1 )
{
ret = poll( fds, 2, -1 );
if( ret < 0 )
{
printf( "poll failure\n" );
break;
}
if( fds[1].revents & POLLRDHUP )
{
printf( "server close the connection\n" );
break;
}
else if( fds[1].revents & POLLIN )
{
memset( read_buf, '\0', BUFFER_SIZE );
int len = recv( fds[1].fd, read_buf, BUFFER_SIZE-1, 0 );
int i;
for(i = 0;i<len;i++)printf("%c",read_buf[i]);
}
if( fds[0].revents & POLLIN )
{
ret = splice( 0, NULL, pipefd[1], NULL, 32768, SPLICE_F_MORE | SPLICE_F_MOVE );
ret = splice( pipefd[0], NULL, sockfd, NULL, 32768, SPLICE_F_MORE | SPLICE_F_MOVE );
}
}
close( sockfd );
return 0;
}原文地址：http://blog.csdn.net/fangjian1204/article/details/38415017
