一、Select缺点

 

二、服务器端 

#include <stdio.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <sys/select.h>int main() {// 创建socketint lfd = socket(PF_INET, SOCK_STREAM, 0);struct sockaddr_in saddr;saddr.sin_port = htons(9999);saddr.sin_family = AF_INET;saddr.sin_addr.s_addr = INADDR_ANY;// 绑定bind(lfd, (struct sockaddr *)&saddr, sizeof(saddr));// 监听listen(lfd, 8);// 创建一个fd_set的集合，存放的是需要检测的文件描述符fd_set rdset, tmp;FD_ZERO(&rdset);FD_SET(lfd, &rdset);int maxfd = lfd;while(1) {tmp = rdset;// 调用select系统函数，让内核帮检测哪些文件描述符有数据int ret = select(maxfd + 1, &tmp, NULL, NULL, NULL);if(ret == -1) {perror("select");exit(-1);} else if(ret == 0) {continue;} else if(ret > 0) {// 说明检测到了有文件描述符的对应的缓冲区的数据发生了改变if(FD_ISSET(lfd, &tmp)) {// 表示有新的客户端连接进来了struct sockaddr_in cliaddr;int len = sizeof(cliaddr);int cfd = accept(lfd, (struct sockaddr *)&cliaddr, &len);// 将新的文件描述符加入到集合中FD_SET(cfd, &rdset);// 更新最大的文件描述符maxfd = maxfd > cfd ? maxfd : cfd;}int i = lfd + 1;for(i; i <= maxfd; i++) {if(FD_ISSET(i, &tmp)) {// 说明这个文件描述符对应的客户端发来了数据char buf[1024] = {0};int len = read(i, buf, sizeof(buf));if(len == -1) {perror("read");exit(-1);} else if(len == 0) {printf("client closed...\n");close(i);FD_CLR(i, &rdset);} else if(len > 0) {printf("read buf = %s\n", buf);write(i, buf, strlen(buf) + 1);}}}}}close(lfd);return 0;
}

三、客户端

#include <stdio.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>int main() {// 创建socketint fd = socket(PF_INET, SOCK_STREAM, 0);if(fd == -1) {perror("socket");return -1;}struct sockaddr_in seraddr;inet_pton(AF_INET, "127.0.0.1", &seraddr.sin_addr.s_addr);seraddr.sin_family = AF_INET;seraddr.sin_port = htons(9999);// 连接服务器int ret = connect(fd, (struct sockaddr *)&seraddr, sizeof(seraddr));if(ret == -1){perror("connect");return -1;}int num = 0;while(1) {char sendBuf[1024] = {0};sprintf(sendBuf, "send data %d", num++);write(fd, sendBuf, strlen(sendBuf) + 1);// 接收int len = read(fd, sendBuf, sizeof(sendBuf));if(len == -1) {perror("read");return -1;}else if(len > 0) {printf("read buf = %s\n", sendBuf);} else {printf("服务器已经断开连接...\n");break;}// sleep(1);usleep(1000);}close(fd);return 0;
}