Linux下一个单进程并发服务器的实例 使用select

/*单进程并发服务器实例。该程序采用单进程并发服务器算法实现的。*/
#include <stdio.h>        
#include <string.h>         
#include <unistd.h>      
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/time.h>
#include <stdlib.h>

#define PORT 1234           //服务器端口
#define BACKLOG 5           //listen队列中等待的连接数
#define MAXDATASIZE 1024 //缓冲区大小

typedef struct _CLIENT{        //客户端结构体
int       fd;        //客户端socket描述符
char*  name;
struct sockaddr_in addr;     //客户端地址信息结构体
char* data;                                      
} CLIENT;
void process_cli(CLIENT *client, char* recvbuf, int len);  //客户请求处理函数
void savedata(char* recvbuf, int len, char* data);

main()
{
int    i, maxi, maxfd,sockfd;
int    nready;
ssize_t      n;
fd_set      rset, allset;    //select所需的文件描述符集合
int listenfd, connectfd;     //socket文件描述符
struct sockaddr_in server;     //服务器地址信息结构体

CLIENT client[FD_SETSIZE];     //FD_SETSIZE为select函数支持的最大描述符个数
char recvbuf[MAXDATASIZE];    //缓冲区
int sin_size;            //地址信息结构体大小

if ((listenfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {    //调用socket创建用于监听客户端的socket
perror("Creating socket failed.");
exit(1);
}

int opt = SO_REUSEADDR;
setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));    //设置socket属性

bzero(&server,sizeof(server));
server.sin_family=AF_INET;
server.sin_port=htons(PORT);
server.sin_addr.s_addr = htonl (INADDR_ANY);

if (bind(listenfd, (struct sockaddr *)&server, sizeof(struct sockaddr)) == -1) {    //调用bind绑定地址
perror("Bind error.");
exit(1);
}  

if(listen(listenfd,BACKLOG) == -1){      //调用listen开始监听
perror("listen() error\n");
exit(1);
}

sin_size=sizeof(struct sockaddr_in);
//初始化select
maxfd = listenfd;    
maxi = -1;              
for (i = 0; i < FD_SETSIZE; i++) {
client[i].fd = -1; 
}
FD_ZERO(&allset);        //清空
FD_SET(listenfd, &allset);    //将监听socket加入select检测的描述符集合

while(1)
{
struct sockaddr_in addr;
rset = allset;           
nready = select(maxfd+1, &rset, NULL, NULL, NULL);    //调用select
printf("select saw rset actions and the readfset num is %d. \n",nready );

if (FD_ISSET(listenfd, &rset)) {      //检测是否有新客户端请求
printf("accept a connection.\n");
//调用accept，返回服务器与客户端连接的socket描述符
if ((connectfd = accept(listenfd,(struct sockaddr *)&addr,(socklen_t *)&sin_size))==-1) {
perror("accept() error\n");
continue;
}

//将新客户端的加入数组
for (i = 0; i < FD_SETSIZE; i++){
if (client[i].fd < 0) {
client[i].fd = connectfd;    //保存客户端描述符
client[i].name = new char[MAXDATASIZE];
client[i].addr = addr;
client[i].data = new char[MAXDATASIZE];
client[i].name[0] = '\0';
client[i].data[0] = '\0';
printf("You got a connection from %s.  ",inet_ntoa(client[i].addr.sin_addr) );
break;
}
}   

printf("add new connect fd.\n");
if (i == FD_SETSIZE)         
printf("too many clients\n");
FD_SET(connectfd, &allset);   //将新socket连接放入select监听集合
if (connectfd > maxfd) 
maxfd = connectfd;   //确认maxfd是最大描述符
if (i > maxi)          //数组最大元素值
maxi = i;         
if (--nready <= 0)
continue;      //如果没有新客户端连接，继续循环
}

for (i = 0; i <= maxi; i++) {    
if ( (sockfd = client[i].fd) < 0)       //如果客户端描述符小于0，则没有客户端连接，检测下一个
continue;

if (FD_ISSET(sockfd, &rset)) {        //检测此客户端socket是否有数据   
printf("recv occured for connect fd[%d].\n",i);
if ( (n = recv(sockfd, recvbuf, MAXDATASIZE,0)) == 0) { //从客户端socket读数据，等于0表示网络中断
close(sockfd);        //关闭socket连接
printf("Client( %s ) closed connection. User's data: %s\n",client[i].name,client[i].data);
FD_CLR(sockfd, &allset);    //从监听集合中删除此socket连接
client[i].fd = -1;        //数组元素设初始值，表示没客户端连接
delete client[i].name;
delete client[i].data;
} else
process_cli(&client[i], recvbuf, n);    //接收到客户数据，开始处理
if (--nready <= 0)    
break;       //如果没有新客户端有数据，跳出for循环回到while循环
}
}
}
close(listenfd);  //关闭服务器监听socket    
}

void process_cli(CLIENT *client, char* recvbuf, int len)
{
char sendbuf[MAXDATASIZE];

recvbuf[len-1] = '\0';
if (strlen(client->name) == 0) {
memcpy(client->name,recvbuf, len);
printf("Client's name is %s.\n",client->name);
return;
}

printf("Received client( %s ) message: %s\n",client->name, recvbuf);
savedata(recvbuf,len, client->data);
for (int i1 = 0; i1 < len - 1; i1++) {
sendbuf[i1] = recvbuf[len - i1 -2];
}
sendbuf[len - 1] = '\0';

send(client->fd,sendbuf,strlen(sendbuf),0);
}

void savedata(char* recvbuf, int len, char* data)
{
int start = strlen(data);
for (int i = 0; i < len; i++) {
data[start + i] = recvbuf[i];
}       
}