非阻塞select

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本文展示了如何在C++中使用非阻塞select实现客户端和服务端的连接。客户端通过非阻塞方式进行连接尝试，遇到EINPROGRESS错误时，使用select进行超时控制。服务端使用非阻塞select监听客户端连接，并处理接收和发送数据。

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非阻塞select下载

链接:https://pan.baidu.com/s/1v3wuohyelqGFIRVbUAJ4sg 密码:49vw

select_client客户端

// main.cpp

// 111

// Created by LXBig on 18/4/9.

#include <iostream>

#include <string.h>

#include <stdlib.h>

#include <arpa/inet.h>

#include <sys/socket.h>

#include <unistd.h>

#define BUF_SIZE 1024

#include <fcntl.h>

#include <sys/select.h>

#include<sys/ioctl.h>

#include <sys/types.h>

#include <errno.h>

#include <unistd.h>

//客户端

void setNonBlock(int s,bool noblock)

{

1、获取文件的flags，即open函数的第二个参数:

flags = fcntl(fd,F_GETFL,0);

2、设置文件的flags:

fcntl(fd,F_SETFL,flags);

3、增加文件的某个flags，比如文件是阻塞的，想设置成非阻塞:

int flags = fcntl(s, F_GETFL,&noblock);

flags |= O_NONBLOCK;

fcntl(s,F_SETFL,flags);

}

#define PEER_IP "127.0.0.1"

#define PEER_PORT 1234

void select_sock_client()

{

int ret = 0;

int sock_fd;

struct sockaddr_in addr;

sock_fd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

setNonBlock(sock_fd, true);

memset(&addr, 0, sizeof(sockaddr));

addr.sin_family = AF_INET;

addr.sin_addr.s_addr = inet_addr("127.0.0.1");

addr.sin_port = htons(1234);

int res = connect(sock_fd, (struct sockaddr*)&addr, sizeof(addr));

if (res == 0) {

printf("socket connect succeed immediately.\n");

ret = 0;

}

else

{

printf("get the connect result by select().\n");

if (errno == EINPROGRESS) //EINPROGRESS: Operation now in progress（套接字为非阻塞套接字，且连接请求没有立即完成）

{

int times = 0;

while (true)

{

fd_set rfds, wfds;

struct timeval tv;

printf("errno = %d\n", errno);

FD_ZERO(&rfds);

FD_ZERO(&wfds);

FD_SET(sock_fd, &rfds);

FD_SET(sock_fd, &wfds);

/* set select() time out */

tv.tv_sec = 10;

tv.tv_usec = 0;

int selres = select(sock_fd + 1, &rfds, &wfds, NULL, &tv);

switch (selres)

{

case -1:

printf("select error\n");

ret = -1;

break;

case 0:

printf("select time out\n");

ret = -1;

break;

default:

if (FD_ISSET(sock_fd, &rfds) || FD_ISSET(sock_fd, &wfds))

{

connect(sock_fd, (struct sockaddr *)&addr, sizeof(struct sockaddr_in));

int err = errno;

if (err == EISCONN) //Transport endpoint is already connected（已经连接到该套接字）

{

printf("connect finished 111.\n");

ret = 0;

}

else

{

printf("connect failed. errno = %d\n", errno);

printf("FD_ISSET(sock_fd, &rfds): %d\n FD_ISSET(sock_fd, &wfds): %d\n", FD_ISSET(sock_fd, &rfds) , FD_ISSET(sock_fd, &wfds));

ret = errno;

}

else

{

printf("haha\n");

}

if (-1 != selres && (ret != 0))

{

printf("check connect result again... %d\n", times);

continue;

}

else

{

break;

}

else

{

printf("connect to host %s:%d failed.\n", PEER_IP, PEER_PORT);

ret = errno;

}

if (0 == ret)

{

//获取用户输入的字符串并发送给服务器

char bufSend[40];

printf("input a string: ");

scanf("%s",bufSend);

write(sock_fd, bufSend, strlen(bufSend));

}

else

{

printf("connect to host %s:%d failed.\n", PEER_IP, PEER_PORT);

}

close(sock_fd);

}

int main(int argc, const char * argv[]) {

select_sock_client();

return 0;

}

运行结果

get the connect result by select().

errno = 36

connect finished 111.

input a string: 12345

Program ended with exit code: 0

select_server服务端

// main.cpp

// 222

// Created by LXBig on 18/4/9.

#include <iostream>

//using namespace std;

#include <string.h>

#include <stdlib.h>

#include <unistd.h>

#include <arpa/inet.h>

#include <netinet/in.h>

#include <sys/socket.h>

#include <netdb.h> //DNS头文件

#define BUF_SIZE 1024

#include <set>

#include <fcntl.h>

//服务端

fd_set g_inset;

std::set<int> g_clients;

void setNonBlock(int s,bool noblock)

{

1、取得文件描述符状态、获取文件的flags，即open函数的第二个参数:

flags = fcntl(fd,F_GETFL,0);

O_NONBLOCK ：无延迟。/ 非阻塞

2、设置文件的flags:

fcntl(fd,F_SETFL,flags);

3、增加文件的某个flags，比如文件是阻塞的，想设置成非阻塞:

int flags = fcntl(s, F_GETFL,&noblock);

flags |= O_NONBLOCK;

fcntl(s,F_SETFL,flags);

}

//处理客户端连接

void processAccept(int & server,int & maxfd)

{

struct sockaddr_in clnt_addr;

socklen_t clnt_addr_size = sizeof(clnt_addr);

int clnt_sock = accept(server, (struct sockaddr*)&clnt_addr, &clnt_addr_size);

//添加到g_clients进行管理，并设置到g_inset中，在下次循环时监听该套接字

g_clients.insert(clnt_sock);

FD_SET(clnt_sock,&g_inset);//将套接字添加到set中

setNonBlock(clnt_sock, true);//将客户端设置为非阻塞

if (maxfd < clnt_sock) {

maxfd = clnt_sock;

}

//客户端发送消息

bool prvessClient(int & client)

{

char buf[512];

//接收并且打印数据

ssize_t n = read(client, buf, sizeof(buf)-1);

if (n > 0) {

printf("server recv %zd byte: %s\n",n,buf);

//发送回客户端并关闭客户端

n = write(client, buf, n);

}

else if (n == 0)

{

close(client);

return false;

}

return true;

}

void select_sock_server()

{

int err = 0;

int maxfd = 0;

//创建一个tcp Socket

int serv_sock = socket(AF_INET, SOCK_STREAM, 0);

maxfd = serv_sock;

setNonBlock(serv_sock, true); //设置非阻塞

//将套接字和IP、端口绑定

struct sockaddr_in serv_addr;

memset(&serv_addr, 0, sizeof(serv_addr));//每个字节都用0填充

serv_addr.sin_family = AF_INET;//使用IPV4地址

serv_addr.sin_addr.s_addr = inet_addr("127.0.0.1");//具体的IP地址

serv_addr.sin_port = htons(1234);//端口

bind(serv_sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr));

//进入监听状态，等待用户发起请求

err = listen(serv_sock, 20);

if (err == -1) {

std::cout<<"error!"<<std::endl;

return ;

}

//设置select函数的等待时间

timeval t;

t.tv_sec = 0;

t.tv_usec = 1000;

//清空全局的fd可读集合，将服务器的监听socket()函数添加进去

FD_ZERO(&g_inset);

FD_SET(serv_sock,&g_inset);

do {

//每次都重置 inset ，这样只需要维护好 g_inset即可

fd_set inset = g_inset;

int ret = select(maxfd+1, &inset, nullptr, nullptr, &t);

if (ret > 0) {

printf("******************\n");

//如果是服务器准备就绪，说明有客户端连接

if (FD_ISSET(serv_sock,&inset)) {

processAccept(serv_sock, maxfd);

--ret;

}

//判断是否有客户端套接字就绪，有则处理

for (std::set<int>::iterator iter = g_clients.begin(); iter != g_clients.end() && ret > 0 ;)

{

int client = *iter;

if (FD_ISSET(client,&inset)) {

--ret;

//如果客户端关闭从 g_inset 和 g_clients中清空该客户端

if(!prvessClient(client))

{

FD_CLR(client,&g_inset);

g_clients.erase(iter++);

continue;

}

++iter;

}

//当select()函数触发的事件处理完，会提前结束遍历。

}

} while (true);

}

int main(int argc, const char * argv[]) {

select_sock_server();

return 0;

}

的出结果

******************

server recv 5 byte: 12345

******************