Linux下的异步TCP socket及实例
Linux下的异步TCP socket及实例
- 同步socket通讯时，程序会阻塞在诸如(connect、accept、recv、recvfrom)等操作上，直到有事件发生时才会继续。
- 而在异步通讯交互中，两方可以任意发送消息，当有数据要接收时，会收到系统消息提示来接收数据，而不会阻塞。
- 在Linux下基于socket的异步通讯可以有多种方式，比较常用的有select方式、epoll方式和异步消息的方式。
一、 select方式：
- 设置放置socket句柄的集合变量
- 把要判断的socket句柄放到集合
- 设置超时时间
- 执行select操作
- 根据select操作返回值做相应处理（连接、读、写等）
例子：
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#define MYPORT i 1234 // the port users will be connecting to
#define BACKLOG 5 // how many pending connections queue will hold
#define BUF_SIZE 200
int fd_A[BACKLOG]; // accepted connection fd
int conn_amount; // current connection amount
void showclient()
{
int i;
printf("client amount: %d\n", conn_amount);
for (i = 0; i < BACKLOG; i++) {
printf("[%d]:%d ", i, fd_A[i]);
}
printf("\n\n");
}
int main(void)
{
int sock_fd, new_fd; // listen on sock_fd, new connection on new_fd
struct sockaddr_in server_addr; // server address information
struct sockaddr_in client_addr; // connector's address information
socklen_t sin_size;
int yes = 1;
char buf[BUF_SIZE];
int ret;
int i;
if ((sock_fd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
perror("socket");
exit(1);
}
if (setsockopt(sock_fd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int)) == -1) {
perror("setsockopt");
exit(1);
}
server_addr.sin_family = AF_INET; // host byte order
server_addr.sin_port = htons(MYPORT); // short, network byte order
server_addr.sin_addr.s_addr = INADDR_ANY; // automatically fill with my IP
memset(server_addr.sin_zero, '', sizeof(server_addr.sin_zero));
if (bind(sock_fd, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1) {
perror("bind");
exit(1);
}
if (listen(sock_fd, BACKLOG) == -1) {
perror("listen");
exit(1);
}
printf("listen port %d\n", MYPORT);
fd_set fdsr;
int maxsock;
struct timeval tv;
conn_amount = 0;
sin_size = sizeof(client_addr);
maxsock = sock_fd;
while (1) {
// initialize file descriptor set
FD_ZERO(&fdsr);
FD_SET(sock_fd, &fdsr);
// timeout setting
tv.tv_sec = 30;
tv.tv_usec = 0;
// add active connection to fd set
for (i = 0; i < BACKLOG; i++) {
if (fd_A[i] != 0) {
FD_SET(fd_A[i], &fdsr);
}
}
ret = select(maxsock + 1, &fdsr, NULL, NULL, &tv);
if (ret < 0) {
perror("select");
break;
} else if (ret == 0) {
printf("timeout\n");
continue;
}
// check every fd in the set
for (i = 0; i < conn_amount; i++) {
if (FD_ISSET(fd_A[i], &fdsr)) {
ret = recv(fd_A[i], buf, sizeof(buf), 0);
if (ret <= 0) { // client close
printf("client[%d] close\n", i);
close(fd_A[i]);
FD_CLR(fd_A[i], &fdsr);
fd_A[i] = 0;
}
else { // receive data
if (ret < BUF_SIZE)
memset(&buf[ret], '', 1);
printf("client[%d] send:%s\n", i, buf);
}
}
}
// check whether a new connection comes
if (FD_ISSET(sock_fd, &fdsr)) {
new_fd = accept(sock_fd, (struct sockaddr *)&client_addr, &sin_size);
if (new_fd <= 0) {
perror("accept");
continue;
}
// add to fd queue
if (conn_amount < BACKLOG) {
fd_A[conn_amount++] = new_fd;
printf("new connection client[%d] %s:%d\n", conn_amount,inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port));
if (new_fd > maxsock)
maxsock = new_fd;
}
else {
printf("max connections arrive, exit\n");
send(new_fd, "bye", 4, 0);
close(new_fd);
break;
}
}
showclient();
}
// close other connections
for (i = 0; i < BACKLOG; i++) {
if (fd_A[i] != 0) {
close(fd_A[i]);
}
}
return 0;
}
二、 epool方式
- 用epoll_create建立epool句柄
- 控制socket行为epoll_ctl
- 等待socket状态处理epoll_wait
例子：
#include <sys/socket.h>
#include <sys/epoll.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <iostream>
using namespace std;
#define MAX_EVENTS 500
struct myevent_s
{
int fd;
void (*call_back)(int fd, int events, void *arg);
int events;
void *arg;
int status; // 1: in epoll wait list, 0 not in
char buff[128]; // recv data buffer
int len;
long last_active; // last active time
};
// set event
void EventSet(myevent_s *ev, int fd, void (*call_back)(int, int, void*), void *arg)
{
ev->fd = fd;
ev->call_back = call_back;
ev->events = 0;
ev->arg = arg;
ev->status = 0;
ev->last_active = time(NULL);
}
// add/mod an event to epoll
void EventAdd(int epollFd, int events, myevent_s *ev)
{
struct epoll_event epv = {0, {0}};
int op;
epv.data.ptr = ev;
epv.events = ev->events = events;
if(ev->status == 1){
op = EPOLL_CTL_MOD;
}
else{
op = EPOLL_CTL_ADD;
ev->status = 1;
}
if(epoll_ctl(epollFd, op, ev->fd, &epv) < 0)
printf("Event Add failed[fd=%d]\n", ev->fd);
else
printf("Event Add OK[fd=%d]\n", ev->fd);
}
// delete an event from epoll
void EventDel(int epollFd, myevent_s *ev)
{
struct epoll_event epv = {0, {0}};
if(ev->status != 1) return;
epv.data.ptr = ev;
ev->status = 0;
epoll_ctl(epollFd, EPOLL_CTL_DEL, ev->fd, &epv);
}
int g_epollFd;
myevent_s g_Events[MAX_EVENTS+1]; // g_Events[MAX_EVENTS] is used by listen fd
void RecvData(int fd, int events, void *arg);
void SendData(int fd, int events, void *arg);
// accept new connections from clients
void AcceptConn(int fd, int events, void *arg)
{
struct sockaddr_in sin;
socklen_t len = sizeof(struct sockaddr_in);
int nfd, i;
// accept
if((nfd = accept(fd, (struct sockaddr*)&sin, &len)) == -1)
{
if(errno != EAGAIN && errno != EINTR)
{
printf("%s: bad accept", __func__);
}
return;
}
do
{
for(i = 0; i < MAX_EVENTS; i++)
{
if(g_Events[i].status == 0)
{
break;
}
}
if(i == MAX_EVENTS)
{
printf("%s:max connection limit[%d].", __func__, MAX_EVENTS);
break;
}
// set nonblocking
if(fcntl(nfd, F_SETFL, O_NONBLOCK) < 0) break;
// add a read event for receive data
EventSet(&g_Events[i], nfd, RecvData, &g_Events[i]);
EventAdd(g_epollFd, EPOLLIN|EPOLLET, &g_Events[i]);
printf("new conn[%s:%d][time:%d]\n", inet_ntoa(sin.sin_addr), ntohs(sin.sin_port), g_Events[i].last_active);
}while(0);
}
// receive data
void RecvData(int fd, int events, void *arg)
{
struct myevent_s *ev = (struct myevent_s*)arg;
int len;
// receive data
len = recv(fd, ev->buff, sizeof(ev->buff)-1, 0);
EventDel(g_epollFd, ev);
if(len > 0)
{
ev->len = len;
ev->buff[len] = '';
printf("C[%d]:%s\n", fd, ev->buff);
// change to send event
EventSet(ev, fd, SendData, ev);
EventAdd(g_epollFd, EPOLLOUT|EPOLLET, ev);
}
else if(len == 0)
{
close(ev->fd);
printf("[fd=%d] closed gracefully.\n", fd);
}
else
{
close(ev->fd);
printf("recv[fd=%d] error[%d]:%s\n", fd, errno, strerror(errno));
}
}
// send data
void SendData(int fd, int events, void *arg)
{
struct myevent_s *ev = (struct myevent_s*)arg;
int len;
// send data
len = send(fd, ev->buff, ev->len, 0);
ev->len = 0;
EventDel(g_epollFd, ev);
if(len > 0)
{
// change to receive event
EventSet(ev, fd, RecvData, ev);
EventAdd(g_epollFd, EPOLLIN|EPOLLET, ev);
}
else
{
close(ev->fd);
printf("recv[fd=%d] error[%d]\n", fd, errno);
}
}
void InitListenSocket(int epollFd, short port)
{
int listenFd = socket(AF_INET, SOCK_STREAM, 0);
fcntl(listenFd, F_SETFL, O_NONBLOCK); // set non-blocking
printf("server listen fd=%d\n", listenFd);
EventSet(&g_Events[MAX_EVENTS], listenFd, AcceptConn, &g_Events[MAX_EVENTS]);
// add listen socket
EventAdd(epollFd, EPOLLIN|EPOLLET, &g_Events[MAX_EVENTS]);
// bind & listen
sockaddr_in sin;
bzero(&sin, sizeof(sin));
sin.sin_family = AF_INET;
sin.sin_addr.s_addr = INADDR_ANY;
sin.sin_port = htons(port);
bind(listenFd, (const sockaddr*)&sin, sizeof(sin));
listen(listenFd, 5);
}
int main(int argc, char **argv)
{
short port = 12345; // default port
if(argc == 2){
port = atoi(argv[1]);
}
// create epoll
g_epollFd = epoll_create(MAX_EVENTS);
if(g_epollFd <= 0) printf("create epoll failed.%d\n", g_epollFd);
// create & bind listen socket, and add to epoll, set non-blocking
InitListenSocket(g_epollFd, port);
// event loop
struct epoll_event events[MAX_EVENTS];
printf("server running:port[%d]\n", port);
int checkPos = 0;
while(1){
// a simple timeout check here, every time 100, better to use a mini-heap, and add timer event
long now = time(NULL);
for(int i = 0; i < 100; i++, checkPos++) // doesn't check listen fd
{
if(checkPos == MAX_EVENTS) checkPos = 0; // recycle
if(g_Events[checkPos].status != 1) continue;
long duration = now - g_Events[checkPos].last_active;
if(duration >= 60) // 60s timeout
{
close(g_Events[checkPos].fd);
printf("[fd=%d] timeout[%d--%d].\n", g_Events[checkPos].fd, g_Events[checkPos].last_active, now);
EventDel(g_epollFd, &g_Events[checkPos]);
}
}
// wait for events to happen
int fds = epoll_wait(g_epollFd, events, MAX_EVENTS, 1000);
if(fds < 0){
printf("epoll_wait error, exit\n");
break;
}
for(int i = 0; i < fds; i++){
myevent_s *ev = (struct myevent_s*)events[i].data.ptr;
if((events[i].events&EPOLLIN)&&(ev->events&EPOLLIN)) // read event
{
ev->call_back(ev->fd, events[i].events, ev->arg);
}
if((events[i].events&EPOLLOUT)&&(ev->events&EPOLLOUT)) // write event
{
ev->call_back(ev->fd, events[i].events, ev->arg);
}
}
}
// free resource
return 0;
}
三、 异步通知
- 定义信号处理函数
- 设置socket的消息进程id
- 设置socket消息
- 信号等待和处理
例子：
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <signal.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#define MAX_LENTH 1500
#define SIG_FIFO_IO SIGRTMIN+1
static char recv_buf[MAX_LENTH] = {0};
int main(int argc, char *argv[])
{
int sockfd, on = 1;
struct sigaction action;
sigset_t newmask, oldmask;
struct sockaddr_in addr;
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = INADDR_ANY;
addr.sin_port = htons(50001);
if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
perror("Create socket failed");
exit(-1);
}
if (bind(sockfd, (struct sockaddr *)&addr, sizeof(addr)) == -1) {
perror("Bind socket failed");
exit(-1);
}
if (fcntl(sockfd, F_SETOWN, getpid()) == -1) {
perror("Fcntl F_SETOWN failed");
exit(-1);
}
if (fcntl(sockfd, F_SETSIG, SIG_FIFO_IO) == -1) {
perror("Fcntl F_SETSIG failed");
exit(-1);
}
if (ioctl(sockfd, FIOASYNC, &on) == -1) {
perror("Ioctl FIOASYNC failed");
exit(-1);
}
int rcvd_sig, len;
siginfo_t info;
sigemptyset(&newmask);
sigaddset(&newmask, SIG_FIFO_IO);
sigprocmask(SIG_BLOCK, &newmask, &oldmask);
while (1) {
rcvd_sig = sigwaitinfo(&newmask, &info);//siginfo中的_sigpool{si_band, si_fd},其中si_fd为socket的文件描述符值
if (rcvd_sig == -1) {
perror("sigio: sigwaitinfo");
exit(-1);
}
else {
printf("Signal %d, socket fd %d received from socket\n",
rcvd_sig, info.si_fd);
len = recv(sockfd, recv_buf, MAX_LENTH, MSG_DONTWAIT);
if( len>0)
puts( recv_buf);
exit(-1);
}
}
exit(0);
}