从零开始一个http服务器(三)-返回response 构造

2023-08-11 20:07:34

从零开始一个http服务器（三)

代码地址： https://github.com/flamedancer/cserver

git checkout step3

运行：

gcc request.h request.c response.h response.c main.c tools/utils.c tools/utils.h && ./a.out

测试:

浏览器打开 http://127.0.0.1:9734/

response 构造

观察response结构
定义并返回response
测试

观察response结构

上一节,我们成功解析了http的request，但是我们在浏览器访问我们的地址http://127.0.0.1:9734/ 还是无法正常显示。这是因为我们没有给浏览器返回它能读懂的信息。这一节我们的目标是让浏览器正确的显示信息。什么样的才是浏览器能读懂的信息呢？不妨我们用telnet来模拟向百度主页发一个http request,来看看百度主页返回的是什么信息。

伪造一个http request的字符串，注意 headers 中的 Host 代表我们要访问的主机地址。

GET / HTTP/1.1

Host: www.baidu.com

User-Agent: curl/7.54.0

Accept: */*

Content-Type: application/x-www-form-urlencode

再用telnet连接www.baidu.com 并指定80端口（80为http默认端口，telnet默认端口为23）, telnet www.baidu.com 80

复制黏贴上面我们构造的字符串回车后，你应该能看到如下类似的返回结果：

Trying 119.75.216.20...

Connected to www.a.shifen.com.

Escape character is '^]'.

GET / HTTP/1.1

Host: www.baidu.com

User-Agent: curl/7.54.0

Accept: */*

Content-Type: application/x-www-form-urlencode

HTTP/1.1 200 OK

Accept-Ranges: bytes

Cache-Control: private, no-cache, no-store, proxy-revalidate, no-transform

Connection: Keep-Alive

Content-Length: 2381

Content-Type: text/html

Date: Sat, 18 Aug 2018 02:12:08 GMT

Etag: "588604c8-94d"

Last-Modified: Mon, 23 Jan 2017 13:27:36 GMT

Pragma: no-cache

Server: bfe/1.0.8.18

Set-Cookie: BDORZ=27315; max-age=86400; domain=.baidu.com; path=/

<!DOCTYPE html>

<!--STATUS OK--><html> ...</html>

Connection closed by foreign host.

从HTTP/1.1 200 OK开始就是百度放回给我们的结果。让人惊喜的是这种结构和request很类型，除了第一行外。仔细看看:

第一行为 http版本号 response返回码 response返回结果描述
第二行开始为headers
空行后，接body

定义并返回response

根据response的结构有的信息定义我们的结构体.

/* response.h

*/

#include <stdio.h>

#include "tools/utils.h"

#include "request.h"

struct http_response {

    char * version;

    char * code;   // 状态返回码

    char * desc;   // 返回描述

    struct Map * headers;

    char * body;

};

void initHttpResponse(struct http_response * response);

void doResponse(

    struct http_request * request,

    FILE * stream

);

void outputToFile(

    struct http_response * response,

    FILE * stream

);

构造我们的response数据, 我们每次都返回相同的数据.

/* response.c

*/

#include <stdio.h>       /* fprintf  NULL */

#include <string.h>       /* strlen */

#include "response.h"

#include "request.h"

#include "tools/utils.h"

void initHttpResponse(struct http_response * response) {

    response->version = NULL;

    response->code = NULL;

    response->desc = NULL;

    response->headers = NULL;

    response->body = NULL;

}

void doResponse(struct http_request * request, FILE * stream) {

    struct http_response responseInstance;

    struct http_response * response = &responseInstance;

    initHttpResponse(response);

    response->version = "HTTP/1.1";

    response->code = "200";

    response->desc = "OK";

    char * content = "<html>hello everyone</html>";

    char content_len[25];

    sprintf(content_len, "%lu", strlen(content));

    struct Item * item = newItem(

        "Content-Length",

        content_len

    );

    struct Map map_instance;

    initMap(&map_instance);

    response->headers = &map_instance;

    mapPush(response->headers, item);

    response->body = content;

    outputToFile(response, stream);

    // clean

    releaseMap(request->headers);

}

void outputToFile(struct http_response * response, FILE * stream) {

    // output version code desc

    int r = fprintf(stream, "%s %s %s \r\n",

        response->version,

        response->code,

        response->desc

    );

    // output headers

    struct Map* map = response->headers;

    struct List* list;

    struct Item* item;

    int print_item_cnt = 0;

    for(int i=0; i<map->table_len; i++) {

        list = map->table[i];

        if(list == NULL) {

           continue;

        }

        item = list->start;

        while(item != NULL) {

            fprintf(stream, "%s: %s\r\n",

                item->key,

                item->value

            );

            item = item->next;

        }

    }

    // output body

    if(response->body != NULL) {

        fprintf(stream, "\r\n%s", response->body);

    }

}

写一个测试用例，将本应向客服端发送的数据输出到stdout

/* test/responseTest.c

test cmd:

gcc  ../request.h ../request.c ../response.h ../response.c ../tools/utils.h ../tools/utils.c  responseTest.c && ./a.out

*/

#include <stdio.h>

#include "../request.h"

#include "../response.h" 

int main() {

    struct http_request request;

    char data[] = "POST / HTTP/1.1\r\nContent-Length: 3\r\n\r\n111";

    struct Map headers;

    request.headers = &headers;

    parse_request(&request, data);

    doResponse(&request, stdout);

}

cd 到 test 目录

运行： gcc ../request.h ../request.c ../response.h ../response.c ../tools/utils.h ../tools/utils.c responseTest.c && ./a.out

可以看到正确的输出：

---------------------------

method is: POST

url is: /

http version is: HTTP/1.1

the headers are :

{'Content-Length': ' 3'}

body is 111

---------------------------

HTTP/1.1 200 OK

Content-Length: 27

<html>hello everyone</html>

现在修改main函数，加上我们的reponse处理逻辑

/**

run cmd:

gcc request.h request.c response.h response.c main.c tools/utils.c tools/utils.h && ./a.out

*/

#include <sys/types.h>

#include <sys/socket.h>

#include <stdio.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include <unistd.h>

#include <netinet/in.h>

#include <stdlib.h>

#include "request.h"

#include "response.h"

#define MAXREQUESTLEN 50000

void initString(char * c, int length) {

    int i = 0;

    while(i < length) {

        *(c + i) = '\0';

        i++;

    }

}

int main() {

    int server_sockfd, client_sockfd;

    socklen_t server_len, client_len;

    struct sockaddr_in server_address;

    struct sockaddr_in client_address;

    server_sockfd = socket(AF_INET, SOCK_STREAM, 0);

    server_address.sin_family = AF_INET;

    server_address.sin_addr.s_addr = inet_addr("127.0.0.1");

    server_address.sin_port = htons(9734);

    server_len = sizeof(server_address);

    bind(server_sockfd, (struct sockaddr *)&server_address, server_len);

    listen(server_sockfd, 5);

    while(1) {

        char ch[MAXREQUESTLEN];

        initString(ch, MAXREQUESTLEN);

        // char send_str[] = "hello world !\n";

        client_len = sizeof(client_address);

        client_sockfd = accept(server_sockfd,

        (struct sockaddr *)&client_address, &client_len);

        read(client_sockfd, &ch, MAXREQUESTLEN);

        printf("%s\n", ch);

        struct http_request request;

        struct Map headers;

        request.headers = &headers;

        parse_request(&request, ch);

        FILE* fp = fdopen(client_sockfd, "w+");

        doResponse(&request, fp);

        fflush(fp);

        fclose(fp);

        // write(client_sockfd, &send_str, sizeof(send_str)/sizeof(send_str[0]));

    }

}

测试

启动我们的server gcc request.h request.c response.h response.c main.c tools/utils.c tools/utils.h && ./a.out

再在浏览器访问我们的服务器地址 http://127.0.0.1:9734/

现在浏览器能识别我们的返回结果了！

码农公寓

从零开始一个http服务器（三)

response 构造

观察response结构

定义并返回response

测试

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