LINUX网络编程 IO 复用
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参考《linux高性能服务器编程》
LINUX下处理多个连接时候，仅仅使用多线程和原始socket函数，效率十分低下
于是就出现了selelct poll epoll等IO复用函数。
这里讨论性能最优的epoll IO复用
用户将需要关注的socket连接使用IO复用函数放进一个事件表中，每当事件表中有一个或者多个SOCKET连接出现读写请求时候，则进行处理
事件表使用一个额外的文件描述符来标识。文件描述符使用 epoll_create函数创建
#inlclude <sys/epoll.h>
int epoll_create(int size); size参数目前不起作用
操作事件表使用epoll_ctl函数进行控制
操作类型有以下3中
EPOLL_CTL_ADD EPOLL_CTL_MOD EPOLL_CTL_DEL
在一段超时时间内等待事件表上的事件 使用epoll_wait();
函数范例如下:
#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 <errno.h>
#include <string.h>
#include <fcntl.h>
#include <stdlib.h>
#include <sys/epoll.h>
#include <pthread.h>
#define MAX_EVENT_NUMBER 1024
#define BUFFER_SIZE 10
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, bool enable_et )
{
epoll_event event;
event.data.fd = fd;
event.events = EPOLLIN;
if( enable_et )
{
event.events |= EPOLLET;
}
epoll_ctl( epollfd, EPOLL_CTL_ADD, fd, &event );
setnonblocking( fd );
}
void et( epoll_event* events, int number, int epollfd, int listenfd )
{
char buf[ BUFFER_SIZE ];
for ( int i = 0; i < number; i++ )
{
int sockfd = events[i].data.fd;
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 );
addfd( epollfd, connfd, true );
}
else if ( events[i].events & EPOLLIN )
{
printf( "event trigger once\n" );
while( 1 )
{
memset( buf, ‘\0‘, BUFFER_SIZE );
int ret = recv( sockfd, buf, BUFFER_SIZE-1, 0 );
if( ret < 0 )
{
if( ( errno == EAGAIN ) || ( errno == EWOULDBLOCK ) )
{
printf( "read later\n" );
break;
}
close( sockfd );
break;
}
else if( ret == 0 )
{
close( sockfd );
}
else
{
printf( "get %d bytes of content: %s\n", ret, buf );
}
}
}
else
{
printf( "something else happened \n" );
}
}
}
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 );
int 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 );
epoll_event events[ MAX_EVENT_NUMBER ];
int epollfd = epoll_create( 5 );
assert( epollfd != -1 );
addfd( epollfd, listenfd, true );
while( 1 )
{
int ret = epoll_wait( epollfd, events, MAX_EVENT_NUMBER, -1 );
if ( ret < 0 )
{
printf( "epoll failure\n" );
break;
}
et( events, ret, epollfd, listenfd );
}
close( listenfd );
return 0;
}
在尝试一个多线程代码;
#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 <errno.h>
#include <string.h>
#include <fcntl.h>
#include <stdlib.h>
#include <sys/epoll.h>
#include <pthread.h>
#define MAX_EVENT_NUMBER 1024
#define BUFFER_SIZE 10
struct fds
{
int epollfd;
int sockfd;
};
void* worker( void* arg )
{
int sockfd = ( (fds*)arg )->sockfd;
int epollfd = ( (fds*)arg )->epollfd;
printf( "start new thread to receive data on fd: %d\n", sockfd );
char buf[ BUFFER_SIZE ];
memset( buf, ‘\0‘, BUFFER_SIZE );
while( 1 )
{
int ret = recv( sockfd, buf, BUFFER_SIZE-1, 0 );
if( ret == 0 )
{
close( sockfd );
printf( "foreiner closed the connection\n" );
break;
}
else if( ret < 0 )
{
if( errno == EAGAIN )
{
// reset_oneshot( epollfd, sockfd );
printf( "read later\n" );
break;
}
}
else
{
printf( "get content: %s\n", buf );
sleep( 5 );
}
}
printf( "end thread receiving data on fd: %d\n", sockfd );
}
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,bool enable_et)
{
epoll_event event;
event.data.fd = fd;
event.events = EPOLLIN;
if(enable_et){
event.events |= EPOLLET;
}
epoll_ctl(epollfd,EPOLL_CTL_ADD,fd,&event);
setnonblocking(fd);
}
void et(epoll_event* events,int number,int epollfd,int listenfd){
char buf[BUFFER_SIZE];
for(int i = 0; i < number;i++){
int sockfd = events[i].data.fd;
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);
addfd(epollfd,connfd,true);
}else if(events[i].events & EPOLLIN){
/*
printf("event trigger once\n");
while(1){
memset(buf,‘\0‘,BUFFER_SIZE);
int ret = recv(sockfd,buf,BUFFER_SIZE-1,0);
if(ret < 0){
if((errno == EAGAIN) || (errno == EWOULDBLOCK)){
printf("read later\n");
break;
}
close(sockfd);
break;
}else if(ret == 0){
close(sockfd);
}else{
printf("get %d bytes of content: %s \n",ret,buf);
}
}*/
pthread_t thread;
fds fds_for_new_worker;
fds_for_new_worker.epollfd = epollfd;
fds_for_new_worker.sockfd = sockfd;
pthread_create( &thread, NULL, worker, ( void* )&fds_for_new_worker );
}else{
printf("something else happened \n");
}
}
}
int main()
{
int ret = 0;
struct sockaddr_in address;
bzero(&address,sizeof(address));
address.sin_family = AF_INET;
inet_pton(AF_INET,"127.0.0.1",&address.sin_addr);
address.sin_port = htons(1134);
int listenfd = socket(AF_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);
epoll_event events[MAX_EVENT_NUMBER];
int epollfd = epoll_create(5);
assert(epollfd != -1);
addfd(epollfd,listenfd,true);
while(1){
int ret = epoll_wait(epollfd,events,MAX_EVENT_NUMBER,-1);
if(ret < 0){
printf("epoll failure\n");
break;
}
et(events,ret,epollfd,listenfd);
}
close(listenfd);
return 0;
}
多线程版本中 如果我们 连续多次输入会出现一个问题
如果我们连续多次在telnet的客户端输入
服务端会开启多个线程 接受这个socket的输入
显示如下：
fd: 5, sockfdget content: dfdsf
...
start new thread to receive data on fd: 5
fd: 5, sockfdget content: sd
...
start new thread to receive data on fd: 5
fd: 5, sockfdget content: sd
...
start new thread to receive data on fd: 5
fd: 5, sockfdget content: sd
...
start new thread to receive data on fd: 5
fd: 5, sockfdget content: sd
...
start new thread to receive data on fd: 5
fd: 5, sockfdget content: sd
...
start new thread to receive data on fd: 5
fd: 5, sockfdget content: sd
如果多个线程同时操作一个socket 可能出现各种意外情况
那么我们就需要设置socket的EPOLLONESHOT标志
对于连续操作，操作系统最多触发该socket上一次读写异常事件。
代码如下:
#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 <errno.h>
#include <string.h>
#include <fcntl.h>
#include <stdlib.h>
#include <sys/epoll.h>
#include <pthread.h>
#define MAX_EVENT_NUMBER 1024
#define BUFFER_SIZE 10
struct fds
{
int epollfd;
int sockfd;
};
void reset_oneshot( int epollfd, int fd )
{
epoll_event event;
event.data.fd = fd;
event.events = EPOLLIN | EPOLLET | EPOLLONESHOT;
epoll_ctl( epollfd, EPOLL_CTL_MOD, fd, &event );
}
void* worker( void* arg )
{
int sockfd = ( (fds*)arg )->sockfd;
int epollfd = ( (fds*)arg )->epollfd;
printf( "start new thread to receive data on fd: %d\n", sockfd );
char buf[ BUFFER_SIZE ];
memset( buf, ‘\0‘, BUFFER_SIZE );
while( 1 )
{
int ret = recv( sockfd, buf, BUFFER_SIZE-1, 0 );
if( ret == 0 )
{
close( sockfd );
printf( "foreiner closed the connection\n" );
break;
}
else if( ret < 0 )
{
if( errno == EAGAIN )
{
reset_oneshot( epollfd, sockfd );
printf( "read later\n" );
break;
}
}
else
{
printf( "get content: %s\n", buf );
sleep( 5 );
}
}
printf( "end thread receiving data on fd: %d\n", sockfd );
}
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,bool setOneShot)
{
epoll_event event;
event.data.fd = fd;
event.events = EPOLLIN;
event.events |= EPOLLET;
if(setOneShot)
event.events |= EPOLLONESHOT;
epoll_ctl(epollfd,EPOLL_CTL_ADD,fd,&event);
setnonblocking(fd);
}
void et(epoll_event* events,int number,int epollfd,int listenfd){
char buf[BUFFER_SIZE];
for(int i = 0; i < number;i++){
int sockfd = events[i].data.fd;
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);
addfd(epollfd,connfd,true);
}else if(events[i].events & EPOLLIN){
/*
printf("event trigger once\n");
while(1){
memset(buf,‘\0‘,BUFFER_SIZE);
int ret = recv(sockfd,buf,BUFFER_SIZE-1,0);
if(ret < 0){
if((errno == EAGAIN) || (errno == EWOULDBLOCK)){
printf("read later\n");
break;
}
close(sockfd);
break;
}else if(ret == 0){
close(sockfd);
}else{
printf("get %d bytes of content: %s \n",ret,buf);
}
}*/
pthread_t thread;
fds fds_for_new_worker;
fds_for_new_worker.epollfd = epollfd;
fds_for_new_worker.sockfd = sockfd;
pthread_create( &thread, NULL, worker, ( void* )&fds_for_new_worker );
}else{
printf("something else happened \n");
}
}
}
int main()
{
int ret = 0;
struct sockaddr_in address;
bzero(&address,sizeof(address));
address.sin_family = AF_INET;
inet_pton(AF_INET,"127.0.0.1",&address.sin_addr);
address.sin_port = htons(1134);
int listenfd = socket(AF_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);
epoll_event events[MAX_EVENT_NUMBER];
int epollfd = epoll_create(5);
assert(epollfd != -1);
addfd(epollfd,listenfd,false);
while(1){
int ret = epoll_wait(epollfd,events,MAX_EVENT_NUMBER,-1);
if(ret < 0){
printf("epoll failure\n");
break;
}
et(events,ret,epollfd,listenfd);
}
close(listenfd);
return 0;
}
输入
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is ‘^]‘.
1
2
3
4
5
sdfufghbskdjhkbaskjhbkjlsadvfblkajwsvdfbljkashdbkfjhasdfhasjkhD
输出
start new thread to receive data on fd: 5
get content: 1
get content: 2
3
4
get content: 5
sdfufg
get content: hbskdjhkb
get content: askjhbkjl
get content: sadvfblka
get content: jwsvdfblj
get content: kashdbkfj
get content: hasdfhasj
get content: khD
hasj
read later
end thread receiving data on fd: 5
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