io multiplex application -- mini chat program
chat_server.cpp
#define _GNU_SOURCE 1
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <assert.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>
#include <stdlib.h>
#include <poll.h>
#define USER_LIMIT 5 // 最大用户数量
#define BUFFER_SIZE 64 // 读缓冲区大小
#define FD_LIMIT 65535 //文件描述符数量限制
// 客户端数据
struct client_data {
sockaddr_in address; // 客户端 socket 地址
char *write_buf; // 待写到客户端的数据的位置
char buf[BUFFER_SIZE]; // 从客户端读入的数据
};
// 将 fd 设置为非阻塞的
int setnonblocking(int fd) {
int old_option = fcntl(fd, F_GETFL);
int new_option = old_option | O_NONBLOCK;
fcntl(fd, F_SETFL, new_option);
return old_option;
}
int main(int argc, char const *argv[]) {
if(argc <= 2) {
printf("uasge: %s ip_address port_number\n", basename(argv[0]));
return 1;
}
const char *ip = argv[1];
int port = atoi(argv[2]);
int ret = 0;
struct sockaddr_in address;
bzero(&address, sizeof(address));
address.sin_family = AF_INET;
inet_pton(AF_INET, ip, &address.sin_addr);
address.sin_port = htons(port);
int listenfd = socket(PF_INET, SOCK_STREAM, 0);
assert(listenfd >= 0);
ret = bind(listenfd, (struct sockaddr*)&address, sizeof(address));
assert(ret != -1);
ret = listen(listenfd, 5);
assert(ret != -1);
// socket 文件描述符的值映射到 client_data 的下标关联对应的客户数据
client_data *users = new client_data[FD_LIMIT];
pollfd fds[USER_LIMIT + 1];
int user_counter = 0;
for(int i = 1; i <= USER_LIMIT; ++i) {
fds[i].fd = -1;
fds[i].events = 0;
}
fds[0].fd = listenfd;
fds[0].events = POLLIN | POLLERR;
fds[0].revents = 0;
while(1) {
ret = poll(fds, user_counter + 1, -1);
if(ret < 0) {
printf("poll failure\n");
break;
}
// 遍历当前所有的 socket 文件描述符, user_counter + 1 即加上监听 socket 的 listenfd
for(int i = 0; i < user_counter + 1; ++i) {
// 有新的 socket 连接加入
if((fds[i].fd == listenfd) && (fds[i].revents & POLLIN)) {
struct sockaddr_in client_address;
socklen_t client_addrlength = sizeof(client_address);
int connfd = accept(listenfd, (struct sockaddr*)&client_address, &client_addrlength);
if(connfd < 0) {
printf("errno is: %s\n", strerror(errno));
continue;
}
// 如果连接数超过 USER_LIMIT 个则关闭新到的连接
if(user_counter >= USER_LIMIT) {
const char *info = "too many users";
printf("%s\n", info);
send(connfd, info, strlen(info), 0);
close(connfd);
continue;
}
// 当前人数 +1
++user_counter;
// 将客户端的数据映射到 user[connfd]
users[connfd].address = client_address;
// 将当前 socket 设置为非阻塞的
setnonblocking(connfd);
// 设置 poll 监听 connfd 上的 POLLIN, POLLRDHUP 和 POLLERR 事件
fds[user_counter].fd = connfd;
fds[user_counter].events = POLLIN | POLLRDHUP | POLLERR;
fds[user_counter].revents = 0;
printf("come a new user, now have %d users\n", user_counter);
} else if(fds[i].revents & POLLERR) {
// 监听到异常事件
printf("get an error from %d\n", fds[i].fd);
char errors[100];
memset(errors, '\0', 100);
socklen_t length = sizeof(errors);
// 尝试通过 getsockopt 来清除该错误码
if(getsockopt(fds[i].fd, SOL_SOCKET, SO_ERROR, &errors, &length) < 0) {
// 如果 getsockopt 失败则打印这条语句
printf("get socket option failed\n");
}
continue;
} else if(fds[i].revents & POLLRDHUP) {
// 若客户端关闭连接则服务器端也关闭连接
//users[fds[i].fd] = users[fds[user_counter].fd];
close(fds[i].fd);
// 将最后一个 socket 连接移至当前关闭 socket 连接所在的坑位
fds[i] = fds[user_counter];
--i;
--user_counter;
printf("a client left, now have %d users online\n", user_counter);
} else if (fds[i].revents & POLLIN) {
// 可读事件
int connfd = fds[i].fd;
memset(users[connfd].buf, '\0', BUFFER_SIZE);
// 将从客户端接受到的数据放入 buf 中
ret = recv(connfd, users[connfd].buf, BUFFER_SIZE - 1, 0);
printf("get %d bytes of client data %s from %d\n", ret, users[connfd].buf, connfd);
if(ret < 0) {
// 若读取错误则关闭该连接
if(errno != EAGAIN) {
close(connfd);
//users[fds[i].fd] = users[fds[user_counter].fd];
// 将最后一个 socket 连接移至当前关闭 socket 连接所在的坑位
fds[i] = fds[user_counter];
--i;
--user_counter;
}
} else if (ret == 0) {
} else {
// 如果接受到数据, 则通知其他客户端准备写数据
for(int j = 1; j <= user_counter; ++j) {
if(fds[j].fd == connfd) {
continue;
}
fds[j].events |= ~POLLIN;
fds[j].events |= POLLOUT;
users[fds[j].fd].write_buf = users[connfd].buf;
}
}
} else if(fds[i].revents & POLLOUT) {
int connfd = fds[i].fd;
if(!users[connfd].write_buf) {
continue;
}
ret = send(connfd, users[connfd].write_buf, strlen(users[connfd].write_buf), 0);
users[connfd].write_buf = NULL;
fds[i].events |= ~POLLOUT;
fds[i].events |= POLLIN;
}
}
}
delete []users;
close(listenfd);
return 0;
}
chat_client.cpp
#define _GNU_SOURCE 1
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <assert.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <poll.h>
#include <fcntl.h>
#define BUFFER_SIZE 64
int main(int argc, char const *argv[]) {
if(argc <= 2) {
printf("usage: %s ip_address port_number\n", basename(argv[0]));
return 1;
}
const char *ip = argv[1];
int port = atoi(argv[2]);
struct sockaddr_in server_address;
bzero(&server_address, sizeof(server_address));
server_address.sin_family = AF_INET;
inet_pton(AF_INET, ip, &server_address.sin_addr);
server_address.sin_port = htons(port);
int sockfd = socket(PF_INET, SOCK_STREAM, 0);
assert(socket >= 0);
if(connect(sockfd, (struct sockaddr*)&server_address, sizeof(server_address)) < 0) {
printf("connection failed\n");
close(sockfd);
return 1;
}
pollfd fds[2];
fds[0].fd = 0;
fds[0].events = POLLIN;
fds[0].revents = 0;
fds[1].fd = sockfd;
fds[1].events = POLLIN | POLLRDHUP;
fds[1].revents = 0;
char read_buf[BUFFER_SIZE];
int pipefd[2];
int ret = pipe(pipefd);
assert(ret != -1);
while(1) {
ret = poll(fds, 2, -1);
if(ret < 0) {
printf("poll failure\n");
break;
}
if(fds[1].revents & POLLRDHUP) {
printf("server close the connection\n");
break;
} else if(fds[1].revents & POLLIN) {
memset(read_buf, '\0', BUFFER_SIZE);
recv(fds[1].fd, read_buf, BUFFER_SIZE - 1, 0);
printf("%s\n", read_buf);
}
if(fds[0].revents & POLLIN) {
// 通过 splice 0 拷贝将用户数据写到 sockfd 上
ret = splice(0, NULL, pipefd[1], NULL, 32768, SPLICE_F_MORE | SPLICE_F_MOVE);
ret = splice(pipefd[0], NULL, sockfd, NULL, 32786, SPLICE_F_MORE | SPLICE_F_MOVE);
}
}
close(sockfd);
return 0;
}