上一章讲解一些简单笔记

https://blog.csdn.net/jenie/article/details/106267740

今天来一个实例如何实现异步的http请求:按以下四步走

1 init_context  a.pthread_createb.epoll_create2 uninit_contexta.pthread_cancelb.close3 commit()a.准备socketb connectc.protocol   #  dns/http/redis/mysqld.sende.epoll_ctl(add,sockfd);4 callback()a.epoll_wait();b.recv()

#include <stdio.h>
#include <stdlib.h>
#include <string.h>#include <unistd.h>
#include <time.h>
#include <fcntl.h>
#include <errno.h>#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>       /* close */
#include <netdb.h> #include <sys/epoll.h>
#include <pthread.h>#define HTTP_VERSION    "HTTP/1.1"
#define USER_AGENT      "User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:10.0.2) Gecko/20100101 Firefox/10.0.2\r\n"
#define ENCODE_TYPE     "Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8\r\n"
#define CONNECTION_TYPE "Connection: close\r\n"#define BUFFER_SIZE     4096char *host_to_ip(const char *hostname) {struct hostent *host_entry = gethostbyname(hostname);if (host_entry) {return inet_ntoa(*(struct in_addr*)*host_entry->h_addr_list);} else {return NULL;}
}int http_create_socket( char *ip) {int sockfd = socket(AF_INET, SOCK_STREAM, 0);struct sockaddr_in sin = {0};sin.sin_addr.s_addr = inet_addr(ip);sin.sin_port = htons(80);sin.sin_family = AF_INET;if (-1 == connect(sockfd, (struct sockaddr*)&sin, sizeof(struct sockaddr_in))) {return -1;}fcntl(sockfd, F_SETFL, O_NONBLOCK);return sockfd;}char *http_send_request(int sockfd, const char *hostname, const char *resource) {char buffer[BUFFER_SIZE] = {0};int len = sprintf(buffer,"GET %s %s\r\nHost: %s\r\n%s\r\n\r\n",resource, HTTP_VERSION,hostname,CONNECTION_TYPE);printf("==33333333333333333333333==\n");printf("request buffer:%s\n", buffer);send(sockfd, buffer, strlen(buffer), 0);printf("==44444444444444444444444==\n");struct timeval tv;tv.tv_sec = 5;tv.tv_usec = 0;fd_set fdread;FD_ZERO(&fdread);FD_SET(sockfd, &fdread);char *result = malloc(sizeof(int));result[0] = '\0';while (1) {int selection = select(sockfd+1, &fdread, NULL, NULL, &tv);if (!selection || !(FD_ISSET(sockfd, &fdread))) {break;} else {len = recv(sockfd, buffer, BUFFER_SIZE, 0);if (len == 0) break;result = realloc(result, (strlen(result) + len + 1) * sizeof(char));strncat(result, buffer, len);}}return result;}int http_client_commit(const char *hostname, const char *resource) {char *ip = host_to_ip(hostname);int sockfd = http_create_socket(ip);char *content =  http_send_request(sockfd, hostname, resource);if (content == NULL) {printf("have no data\n");}puts(content);close(sockfd);free(content);return 0;
}#define ASYNC_CLIENT_NUM        1024
#define HOSTNAME_LENGTH         128typedef void (*async_result_cb)(const char *hostname, const char *result);struct ep_arg {int sockfd;char hostname[HOSTNAME_LENGTH];async_result_cb cb;
};struct async_context {int epfd;pthread_t thread_id;
};struct http_request {char *hostname;char *resource;
};int http_async_client_commit(struct async_context *ctx, const char *hostname, const char *resource, async_result_cb cb) {char *ip = host_to_ip(hostname);if (ip == NULL) return -1;int sockfd = socket(AF_INET, SOCK_STREAM, 0);struct sockaddr_in sin = {0};sin.sin_addr.s_addr = inet_addr(ip);sin.sin_port = htons(80);sin.sin_family = AF_INET;if (-1 == connect(sockfd, (struct sockaddr*)&sin, sizeof(struct sockaddr_in))) {return -1;}fcntl(sockfd, F_SETFL, O_NONBLOCK);char buffer[BUFFER_SIZE] = {0};int len = sprintf(buffer,"GET %s %s\r\nHost: %s\r\n%s\r\n\r\n",resource, HTTP_VERSION,hostname,CONNECTION_TYPE);printf("request buffer:%s\n", buffer);int slen = send(sockfd, buffer, strlen(buffer), 0);struct ep_arg *eparg = (struct ep_arg*)calloc(1, sizeof(struct ep_arg));if (eparg == NULL) return -1;eparg->sockfd = sockfd;eparg->cb = cb;struct epoll_event ev;ev.data.ptr = eparg;ev.events = EPOLLIN;int ret = epoll_ctl(ctx->epfd, EPOLL_CTL_ADD, sockfd, &ev); return ret;}static void *http_async_client_callback(void *arg) {struct async_context *ctx = (struct async_context*)arg;int epfd = ctx->epfd;while (1) {struct epoll_event events[ASYNC_CLIENT_NUM] = {0};int nready = epoll_wait(epfd, events, ASYNC_CLIENT_NUM, -1);if (nready < 0) {if (errno == EINTR || errno == EAGAIN) {continue;} else {break;}} else if (nready == 0) {continue;}printf("nready:%d\n", nready);int i = 0;for (i = 0;i < nready;i ++) {struct ep_arg *data = (struct ep_arg*)events[i].data.ptr;int sockfd = data->sockfd;char buffer[BUFFER_SIZE] = {0};struct sockaddr_in addr;size_t addr_len = sizeof(struct sockaddr_in);int n = recv(sockfd, buffer, BUFFER_SIZE, 0);data->cb(data->hostname, buffer); //call cbint ret = epoll_ctl(epfd, EPOLL_CTL_DEL, sockfd, NULL);//printf("epoll_ctl DEL --> sockfd:%d\n", sockfd);close(sockfd); /////free(data);}}}struct async_context *http_async_client_init(void) {int epfd = epoll_create(1); // if (epfd < 0) return NULL;struct async_context *ctx = calloc(1, sizeof(struct async_context));if (ctx == NULL) {close(epfd);return NULL;}ctx->epfd = epfd;int ret = pthread_create(&ctx->thread_id, NULL, http_async_client_callback, ctx);if (ret) {perror("pthread_create");return NULL;}usleep(1); return ctx;}int http_async_client_uninit(struct async_context *ctx) {close(ctx->epfd);pthread_cancel(ctx->thread_id);return 0;
}struct http_request reqs[] = {{"api.seniverse.com", "/v3/weather/now.json?key=0pyd8z7jouficcil&location=beijing&language=zh-Hans&unit=c" },{"api.seniverse.com", "/v3/weather/now.json?key=0pyd8z7jouficcil&location=changsha&language=zh-Hans&unit=c" },{"api.seniverse.com", "/v3/weather/now.json?key=0pyd8z7jouficcil&location=shenzhen&language=zh-Hans&unit=c" },{"api.seniverse.com", "/v3/weather/now.json?key=0pyd8z7jouficcil&location=shanghai&language=zh-Hans&unit=c" },{"api.seniverse.com", "/v3/weather/now.json?key=0pyd8z7jouficcil&location=tianjin&language=zh-Hans&unit=c" },{"api.seniverse.com", "/v3/weather/now.json?key=0pyd8z7jouficcil&location=wuhan&language=zh-Hans&unit=c" },{"api.seniverse.com", "/v3/weather/now.json?key=0pyd8z7jouficcil&location=hefei&language=zh-Hans&unit=c" },{"api.seniverse.com", "/v3/weather/now.json?key=0pyd8z7jouficcil&location=hangzhou&language=zh-Hans&unit=c" },{"api.seniverse.com", "/v3/weather/now.json?key=0pyd8z7jouficcil&location=nanjing&language=zh-Hans&unit=c" },{"api.seniverse.com", "/v3/weather/now.json?key=0pyd8z7jouficcil&location=jinan&language=zh-Hans&unit=c" },{"api.seniverse.com", "/v3/weather/now.json?key=0pyd8z7jouficcil&location=taiyuan&language=zh-Hans&unit=c" },{"api.seniverse.com", "/v3/weather/now.json?key=0pyd8z7jouficcil&location=wuxi&language=zh-Hans&unit=c" },{"api.seniverse.com", "/v3/weather/now.json?key=0pyd8z7jouficcil&location=suzhou&language=zh-Hans&unit=c" },
};static void http_async_client_result_callback(const char *hostname, const char *result) {printf("hostname:%s, result:%s\n\n\n\n", hostname, result);}int main(int argc, char *argv[]) {#if 0int count = sizeof(reqs) / sizeof(reqs[0]);int i = 0;for (i = 0;i < count;i ++) {http_client_commit(reqs[i].hostname, reqs[i].resource);}#elsestruct async_context *ctx = http_async_client_init();if (ctx == NULL) return -1;int count = sizeof(reqs) / sizeof(reqs[0]);int i = 0;for (i = 0;i < count;i ++) {http_async_client_commit(ctx, reqs[i].hostname, reqs[i].resource, http_async_client_result_callback);}getchar();
#endif}

gcc -o async_http async_http.c  -pthread./async_http

nready:1
hostname:, result:HTTP/1.1 200 OK
Date: Fri, 22 May 2020 11:24:44 GMT
Content-Type: application/json; charset=utf-8
Content-Length: 263
Connection: close
X-Instance-Id: 48ea5e05-e8a6-4732-88fc-92d75c03f819
X-RateLimit-Limit-hour: 400
X-RateLimit-Remaining-hour: 390
X-Powered-By: Express
ETag: W/"107-jmbiYCctU5xHZvZwLKBQFaq+8Q4"
X-Kong-Upstream-Latency: 3
X-Kong-Proxy-Latency: 15
Via: kong/0.14.1{"results":[{"location":{"id":"WWE0TGW4PX6N","name":"济南","country":"CN","path":"济南,济南,山东,中国","timezone":"Asia/Shanghai","timezone_offset":"+08:00"},"now":{"text":"晴","code":"0","temperature":"27"},"last_update":"2020-05-22T18:51:00+08:00"}]}request buffer:GET /v3/weather/now.json?key=0pyd8z7jouficcil&location=taiyuan&language=zh-Hans&unit=c HTTP/1.1
Host: api.seniverse.com
Connection: closerequest buffer:GET /v3/weather/now.json?key=0pyd8z7jouficcil&location=wuxi&language=zh-Hans&unit=c HTTP/1.1
Host: api.seniverse.com
Connection: closenready:1
hostname:, result:HTTP/1.1 200 OK
Date: Fri, 22 May 2020 11:24:44 GMT
Content-Type: application/json; charset=utf-8
Content-Length: 263
Connection: close
X-Instance-Id: 48ea5e05-e8a6-4732-88fc-92d75c03f819
X-RateLimit-Limit-hour: 400
X-RateLimit-Remaining-hour: 389
X-Powered-By: Express
ETag: W/"107-qIPUvgpfAqSASWxasY0cX7/kHDs"
X-Kong-Upstream-Latency: 1
X-Kong-Proxy-Latency: 25
Via: kong/0.14.1{"results":[{"location":{"id":"WW8P3NH2TPDT","name":"太原","country":"CN","path":"太原,太原,山西,中国","timezone":"Asia/Shanghai","timezone_offset":"+08:00"},"now":{"text":"晴","code":"0","temperature":"29"},"last_update":"2020-05-22T18:51:00+08:00"}]}nready:1
hostname:, result:HTTP/1.1 200 OK
Date: Fri, 22 May 2020 11:24:44 GMT
Content-Type: application/json; charset=utf-8
Content-Length: 266
Connection: close
X-Instance-Id: 48ea5e05-e8a6-4732-88fc-92d75c03f819
X-RateLimit-Limit-hour: 400
X-RateLimit-Remaining-hour: 388
X-Powered-By: Express
ETag: W/"10a-EJbpfcFnewi3WWw2VMYKiH1hTiU"
X-Kong-Upstream-Latency: 2
X-Kong-Proxy-Latency: 9
Via: kong/0.14.1{"results":[{"location":{"id":"WTTE97PU94T9","name":"无锡","country":"CN","path":"无锡,无锡,江苏,中国","timezone":"Asia/Shanghai","timezone_offset":"+08:00"},"now":{"text":"多云","code":"4","temperature":"25"},"last_update":"2020-05-22T18:51:00+08:00"}]}request buffer:GET /v3/weather/now.json?key=0pyd8z7jouficcil&location=suzhou&language=zh-Hans&unit=c HTTP/1.1
Host: api.seniverse.com
Connection: closenready:1
hostname:, result:HTTP/1.1 200 OK
Date: Fri, 22 May 2020 11:24:44 GMT
Content-Type: application/json; charset=utf-8
Content-Length: 266
Connection: close
X-Instance-Id: 48ea5e05-e8a6-4732-88fc-92d75c03f819
X-RateLimit-Limit-hour: 400
X-RateLimit-Remaining-hour: 387
X-Powered-By: Express
ETag: W/"10a-gvE2bZhbXqxBpE6pM9cXpdtHZO4"
X-Kong-Upstream-Latency: 4
X-Kong-Proxy-Latency: 9
Via: kong/0.14.1{"results":[{"location":{"id":"WTTDPCGXTWUS","name":"苏州","country":"CN","path":"苏州,苏州,江苏,中国","timezone":"Asia/Shanghai","timezone_offset":"+08:00"},"now":{"text":"多云","code":"4","temperature":"23"},"last_update":"2020-05-22T18:51:00+08:00"}]}

代理自己简单走读一下，就很容易理解。

大家看一下这句代码很有意思，为什么要这么做？ 

其实目的就是主线程和子线程的关系。如果创建子线程，是主线程跑还是子线程跑？

    usleep(1); 

涉及到操作系统原理。通常情况是主线程先跑，因为创建的子线程是放到操作系统调试的就绪队列，等到下个时间片处理。

但有一种情况，刚好这时主线程要时间片到了，这个时候子线程在跑。为了避免问题，特别是在写服务器的时候（今天这个程序是客户端），需要让子线程跑，这样的话，停那么一点点，让子线程先跑。因为加上了 usleep(1).

另外还有一点，申请资源时，资料要如何free，一发时申请，一接收时再释放资源。