select同时处理普通数据及带外数据

#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#incldue <assert.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>
#include <stdlib.h>

int main(int argc, char* argv[])
{
if(argc <= 2){
printf("args err");
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(ret != -1);
ret = listen(listenfd, 5);
assert(ret != -1);

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:%d", errno);
close(listenfd);
}

char buf[1024];
fd_set read_fds;
fd_set exception_fds;
FD_ZERO(&read_fds);
FD_ZERO(&exception_fds);

while(1)
{
memset(buf, '\0', sizeof(buf));
/*
*每次调用select前都要重新在read_fds和exception_fds中设置文件描述符connfd，
*因为事件发生后，文件描述符集合将被内核修改。
**/
FD_SET(connfd, &read_fds);
FD_SET(connfd, &exception_fds);

ret = select(connfd+1, &read_fds, NULL, &exception_fds, NULL);
if(ret < 0){
printf("selection failure\n");
break;
}

if(FD_ISSET(connfd, &read_fds))
{
//可读事件，采用普通recv函数读取数据
ret = recv(connfd, buf, sizeof(buf)-1, 0);//最后一个参数为0
if(ret < 0){
break;
}
printf("获取%d的数据:%s\n", ret, buf);
}
else if(FD_ISSET(connfd, &exception_fds))//
{
//异常事件，采用带MSG_OOB标志的recv函数读取带外数据
ret = recv(connfd, buf, sizeof(buf)-1, MSG_OOB);//最后一个参数为MSG_OOB
if(ret <= 0){
break;
}
printf("获取%d的数据:%s\n", ret, buf);
}
}

close(connfd);
close(listenfd);

return 0;
}