C语言TCP服务器模型 : select + 多线程与双循环单线程阻塞服务器的比较

观察到的实验现象:

启动三个客户端:

使用双循环阻塞服务器:只能accept后等待收发,同时只能与一个客户端建立连接,必须等已连接的客户端多次收发 明确断开后才能与下个客户端连接

使用IO多路复用select:可以同时接收所有的连接请求,并且连接状态一直是存活的,直到客户端关闭连接

select + 多线程服务器创作灵感:

本来是想 接收,发送 全用select

但是如果每个连接都要求处理大量数据,则响应时间不确定

最重要的,select判断依据是内核缓存是否有足够空间可写,而不是数据是否准备好

所以为了数据准备好再发送 

我使用了 接收多路复用+分线程处理数据+处理完毕在线程内直接发送 的模型

什么样的场景收发都适合用select?

IO密集型转发服务器

用于对比的双循环阻塞服务器工作原理:

进入外循环, accept后 再进入内循环 收 发 ,当客户端结束连接时 内层循环结束(使用break)

代码走完 重新进入外层循环 accept阻塞等待一个新连接

注意事项: ip地址修改为符合 你网络规范的ip 运行环境:unix-like系统 gnu_c库

select + 多线程服务器,欢迎指正:

#define _GNU_SOURCE
#include <stdio.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/select.h>
#include <sys/types.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <pthread.h>
#include <signal.h>
#include <time.h>#define SERVER_IP "192.168.142.132"
#define SERVER_PORT 50012
// 此结构体用于线程参数
struct t_args
{int fd;char data[1024];
};
// 用于accept返回的fd的容器
int client_sockfds[1024] = {0};
// 计数器可以理解为指针,每次用完向后挪1位
int count = 0;
// 线程执行函数
void *start_routine(void *p)
{// 解析参数struct t_args ta = *((struct t_args *)p);// fd后面要用int fd = ta.fd;// 数据打印出来表示已经获取,可以进行后续处理printf("%s\n", ta.data);// 模拟数据处理sleep((rand() % 3) + 1);// 这是处理完的结果char res_data[128] = "yes yes done done done";ssize_t send_bytes;// 声明写监控集fd_set writefds;// 清空重置FD_ZERO(&writefds);// 将这个fd加入写监控FD_SET(fd, &writefds);// 如果select返回,说明此fd写就绪int r = select(fd + 1, NULL, &writefds, NULL, NULL);if (r == -1){perror("select");}if (r > 0){// 如果写就绪if (FD_ISSET(fd, &writefds)){// 就把处理好的数据发送回去send_bytes = send(fd, res_data, strlen(res_data), 0);if (send_bytes == -1){perror("send");}if (send_bytes > 0){printf("%s\n", res_data);}}}free(p);pthread_exit(NULL);
}
void handler(void *p)
{pthread_t tid;// 创建线程,传参fdif (pthread_create(&tid, NULL, start_routine, p)){perror("pthread_create");}// 分离if (pthread_detach(tid)){perror("pthread_detach");}
}int main()
{int server_sockfd, client_sockfd;struct sockaddr_in server_sockaddr, client_sockaddr;memset(&server_sockaddr, 0, sizeof(server_sockaddr));memset(&client_sockaddr, 0, sizeof(client_sockaddr));socklen_t client_sockaddr_len = sizeof(client_sockaddr);socklen_t server_sockaddr_len = sizeof(server_sockaddr);ssize_t recv_bytes;char recv_buf[1024] = {0};fd_set readfds;// 随机数种子srand(time(NULL));// 创建socketserver_sockfd = socket(AF_INET, SOCK_STREAM, 0);if (server_sockfd == -1){perror("socket");}// 端口复用int optval = 1;if (setsockopt(server_sockfd, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval)) == -1){perror("setsockopt");}// 绑定地址端口inet_pton(AF_INET, SERVER_IP, &server_sockaddr.sin_addr.s_addr);server_sockaddr.sin_port = htons(SERVER_PORT);server_sockaddr.sin_family = AF_INET;if (bind(server_sockfd, (struct sockaddr *)&server_sockaddr, server_sockaddr_len) == -1){perror("bind");}// 监听if (listen(server_sockfd, 16) == -1){perror("listen");}printf("server start...\n");// 服务器主循环while (1){// 清空重置读集FD_ZERO(&readfds);// 将server_sockfd加入读集FD_SET(server_sockfd, &readfds);// 假设最大的fd是server_sockfdint fd_max = server_sockfd;int i;// count总是指向当前已填充fd的下一个位置for (i = 0; i < count; i++){// client_sockfds[i]数组储存accept返回的fd ,> 0表示存在fdif (client_sockfds[i] > 0){// 存在fd就加入读监控FD_SET(client_sockfds[i], &readfds);// 更新最大fd的值fd_max = fd_max > client_sockfds[i] ? fd_max : client_sockfds[i];}}// 此处select作用:从读集中选择读就绪int r = select(fd_max + 1, &readfds, NULL, NULL, NULL);if (r > 0){// 如果server_sockfd是读就绪的if (FD_ISSET(server_sockfd, &readfds)){// 说明已经有连接在等待,则accept不会阻塞client_sockfd = accept(server_sockfd, (struct sockaddr *)&client_sockaddr, &client_sockaddr_len);if (client_sockfd == -1){perror("accept");}// count++先读取count的值 后++,把返回的client_sockfd存到数组client_sockfds[count++] = client_sockfd;// 当连接数达到1024时,变得无法处理且有重大安全漏洞if (count == 1024){kill(getpid(), SIGKILL);}}// 此循环用于检查client_sockfds数组已填充部分for (i = 0; i < count; i++){// 检查fd是否读就绪if (FD_ISSET(client_sockfds[i], &readfds)){// 接收消息recv_bytes = recv(client_sockfds[i], recv_buf, sizeof(recv_buf), 0);if (recv_bytes < 0){perror("recv");}else if (recv_bytes == 0){printf("close by peer\n");// 对面关我也关close(client_sockfds[i]);// 将数组上的fd清空client_sockfds[i] = 0;}else{// 向线程传参struct t_args ta;ta.fd = client_sockfds[i];strncpy(ta.data, recv_buf, strlen(recv_buf));// 为每个线程参数动态分配内存空间struct t_args *p = (struct t_args *)malloc(sizeof(ta));if (p == NULL){return -1;}// 赋值*p = ta;// 传入处理函数handler((void *)p);}}}}else if (r == -1){perror("select");}}close(server_sockfd);return 0;
}

双循环阻塞服务器:

#define _GNU_SOURCE
#include <stdio.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <string.h>
#include <unistd.h>#define SERVER_IP "192.168.142.132"
#define SERVER_PORT 50012int main()
{int server_sockfd, client_sockfd;struct sockaddr_in server_sockaddr, client_sockaddr;memset(&server_sockaddr, 0, sizeof(server_sockaddr));memset(&client_sockaddr, 0, sizeof(client_sockaddr));socklen_t client_sockaddr_len = sizeof(client_sockaddr);ssize_t send_bytes, recv_bytes;char send_buf[1024] = "How can I help you today ?";char recv_buf[1024] = {0};server_sockfd = socket(AF_INET, SOCK_STREAM, 0);if (server_sockfd == -1){perror("socket");}int optval = 1;setsockopt(server_sockfd, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval));server_sockaddr.sin_family = AF_INET;inet_pton(AF_INET, SERVER_IP, &server_sockaddr.sin_addr.s_addr);server_sockaddr.sin_port = htons(SERVER_PORT);if (bind(server_sockfd, (struct sockaddr *)&server_sockaddr, sizeof(server_sockaddr)) == -1){perror("bind");}if (listen(server_sockfd, 16) == -1){perror("listen");}printf("server start...\n");while (1){client_sockfd = accept(server_sockfd, (struct sockaddr *)&client_sockaddr, &client_sockaddr_len);if (client_sockfd == -1){perror("accept");}while (1){recv_bytes = recv(client_sockfd, recv_buf, sizeof(recv_buf), 0);if (recv_bytes == -1){perror("recv");}else if (recv_bytes == 0){printf("closed by peer\n");break;}else{printf("%s\n", recv_buf);}send_bytes = send(client_sockfd, send_buf, strlen(send_buf), 0);if (send_bytes == -1){perror("send");}}}close(server_sockfd);return 0;
}

赠送客户端:
 

#define _GNU_SOURCE
#include <stdio.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <time.h>#define SERVER_IP "192.168.142.132"
#define SERVER_PORT 50012int main()
{int client_sockfd;struct sockaddr_in server_sockaddr, client_sockaddr;memset(&server_sockaddr, 0, sizeof(server_sockaddr));memset(&client_sockaddr, 0, sizeof(client_sockaddr));socklen_t client_sockaddr_len = sizeof(client_sockaddr);ssize_t send_bytes, recv_bytes;char send_buf[1024] = {0};char recv_buf[1024] = {0};srand(time(NULL));client_sockfd = socket(AF_INET, SOCK_STREAM, 0);if (client_sockfd == -1){perror("socket");}inet_pton(AF_INET, SERVER_IP, &server_sockaddr.sin_addr.s_addr);server_sockaddr.sin_port = htons(SERVER_PORT);server_sockaddr.sin_family = AF_INET;if (connect(client_sockfd, (struct sockaddr *)&server_sockaddr, sizeof(server_sockaddr)) == -1){perror("connect");}getsockname(client_sockfd, (struct sockaddr *)&client_sockaddr, &client_sockaddr_len);snprintf(send_buf, sizeof(send_buf), "%u:he###llo s???ver !!!",ntohs(client_sockaddr.sin_port));while (1){send_bytes = send(client_sockfd, send_buf, strlen(send_buf), 0);if (send_bytes == -1){perror("send");}recv_bytes = recv(client_sockfd, recv_buf, sizeof(recv_buf), 0);if (recv_bytes == -1){perror("recv");}printf("%s\n", recv_buf);sleep(1);}close(client_sockfd);return 0;
}