select server

#include<stdio.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<unistd.h>
#include<stdlib.h>
#include<errno.h>
#include<arpa/inet.h>
#include<netinet/in.h>
#include<string.h>
#include<signal.h>
#include<sys/wait.h>

#define ERR_EXIT(m) \
do { \
perror(m); \
exit(EXIT_FAILURE); \
} while (0)

int main(void)
{

signal(SIGPIPE, SIG_IGN);
int listenfd; //被动套接字(文件描述符），即只可以accept, 监听套接字
if ((listenfd = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
//  listenfd = socket(AF_INET, SOCK_STREAM, 0)
ERR_EXIT("socket error");

struct sockaddr_in servaddr;
memset(&servaddr, 0, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(5188);
servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
/* servaddr.sin_addr.s_addr = inet_addr("127.0.0.1"); */
/* inet_aton("127.0.0.1", &servaddr.sin_addr); */

int on = 1;
if (setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
ERR_EXIT("setsockopt error");

if (bind(listenfd, (struct sockaddr*)&servaddr,sizeof(servaddr)) < 0)
ERR_EXIT("bind error");

if (listen(listenfd, SOMAXCONN) < 0) //listen应在socket和bind之后，而在accept之前
ERR_EXIT("listen error");

struct sockaddr_in peeraddr; //传出参数
socklen_t peerlen = sizeof(peeraddr); //传入传出参数，必须有初始值

int conn; // 已连接套接字(变为主动套接字，即可以主动connect)
int i;
int client[FD_SETSIZE];
int maxi = 0; // client数组中最大不空闲位置的下标
for (i = 0; i < FD_SETSIZE; i++)
client[i] = -1;

int nready;
int maxfd = listenfd;
fd_set rset;
fd_set allset;
FD_ZERO(&rset);
FD_ZERO(&allset);
FD_SET(listenfd, &allset);

while (1) {
rset = allset;
nready = select(maxfd + 1, &rset, NULL, NULL, NULL);
if (nready == -1) {
if (errno == EINTR)
continue;
ERR_EXIT("select error");
}

if (nready == 0)
continue;

if (FD_ISSET(listenfd, &rset)) {

conn = accept(listenfd, (struct sockaddr*)&peeraddr, &peerlen);  //accept不再阻塞
if (conn == -1)
ERR_EXIT("accept error");

for (i = 0; i < FD_SETSIZE; i++) {
if (client[i] < 0) {
client[i] = conn;
if (i > maxi)
maxi = i;
break;
}
}

if (i == FD_SETSIZE) {
fprintf(stderr, "too many clients\n");
exit(EXIT_FAILURE);
}

printf("recv connect ip=%s port=%d\n", inet_ntoa(peeraddr.sin_addr),
ntohs(peeraddr.sin_port));

FD_SET(conn, &allset);
if (conn > maxfd)
maxfd = conn;

if (--nready <= 0)
continue;
}

for (i = 0; i <= maxi; i++) {
conn = client[i];
if (conn == -1)
continue;

if (FD_ISSET(conn, &rset)) {

char recvbuf[1024] = {0};
int ret = read(conn, recvbuf, 1024);
if (ret == -1)
ERR_EXIT("readline error");
else if (ret  == 0) { //客户端关闭
printf("client close \n");
FD_CLR(conn, &allset);
client[i] = -1;
close(conn);
}

fputs(recvbuf, stdout);
write(conn, recvbuf, strlen(recvbuf));

if (--nready <= 0)
break;
}
}

}

return 0;
}