13 select的优化一

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1. 上个例子中，select通过for循环轮询client套接字，轮询的范围比较大，有优化的地方。

2. 优化代码：

通过数组存储client的套接字，达到少轮询的效果，可以在client数量比较多、读写数据量大的情况下看到效果；

select的最大连接数1024，所以在处理并发量比较小的时候可以用上，如果并发大的时候需要重新考虑。

#include "socket_includes.h"int mz_ipv4_tcp_create_socket(void){int listenfd, sockfd, opt = 1;struct sockaddr_in server, client;socklen_t len;int timep;int ret;listenfd = socket(AF_INET, SOCK_STREAM, 0);if(listenfd < 0){perror("Create socket fail.");return -1;} if((ret = setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt))) < 0){perror("Error, set socket reuse addr failed");  return -1;}bzero(&server, sizeof(server));server.sin_family = AF_INET;server.sin_port   = htons(SERV_PORT);server.sin_addr.s_addr  = htonl(INADDR_ANY);len = sizeof(struct sockaddr);if(bind(listenfd, (struct sockaddr *)&server, len)<0){  perror("bind error.");return -1;}  listen(listenfd, MAX_LISTEN_QUE);return listenfd;}int main(int argc, char *argv[]){int listenfd, sockfd;struct sockaddr_in server, client;socklen_t len;int bytes =0 ;fd_set global_rdfs,current_rdfs;int maxfd;int i;char buf[MAX_BUFFER_SIZE];int client_fd[FD_SETSIZE];len = sizeof(struct sockaddr_in);printf("FD_SETSIZE=%d\n", FD_SETSIZE);listenfd = mz_ipv4_tcp_create_socket();FD_ZERO(&global_rdfs);FD_SET(listenfd, &global_rdfs);maxfd = listenfd;for(i = 0; i < FD_SETSIZE; i++ )client_fd[i] = -1;while(1){current_rdfs = global_rdfs;if(select(maxfd + 1, ¤t_rdfs, NULL, NULL, NULL)<0){perror("select error.\n");return RT_ERR;}if(FD_ISSET(listenfd, ¤t_rdfs)){if((sockfd = accept(listenfd, (struct sockaddr*)&client, (socklen_t*)&len))<0){perror("accept error.\n");return RT_ERR;}printf("sockfd:%d\n", sockfd);FD_CLR(i, ¤t_rdfs);maxfd = maxfd > sockfd ? maxfd :sockfd;FD_SET(sockfd, &global_rdfs);for(i = 0; i < maxfd; i++){if(-1 == client_fd[i]){client_fd[i] = sockfd;break;}}}for(i = 0; i <= maxfd; i++){if(-1 == client_fd[i]){continue;}if(FD_ISSET(client_fd[i], ¤t_rdfs)){printf("read socket:%d\n", client_fd[i]);bytes = recv(client_fd[i], buf, MAX_BUFFER_SIZE, 0);if(bytes < 0){perror("recv error.\n");return RT_ERR;}if(bytes == 0){FD_CLR(client_fd[i], &global_rdfs);close(client_fd[i]);client_fd[i] = -1;continue;}printf("buf:%s\n", buf);send(client_fd[i], buf, strlen(buf), 0);}}}}

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