目标

实现一个高性能静态HTTP服务器。

HTTP协议报文

1. 报文

用于HTTP协议交互的信息。(多行字符串文本)

2. 报文分类：

请求报文：请求端(客户端)的HTTP报文。

响应报文：响应端(服务端)的HTTP报文。

3. 报文结构

请求报文

例如：

响应报文

例如：

常用状态码

状态码

状态码英文名称

中文描述

200

OK

请求成功

301

Moved Permanently

资源(网页等)被永久转移到其它URL

401

Unauthorized

请求要求用户的身份认证

403

Forbidden

服务器理解请求客户端的请求，但是拒绝执行此请求

404

Not Found

请求的资源(网页等)不存在

408

Request Time-out

服务器等待客户端发送的请求时间过长，超时

500

Internal Server Error

服务器内部错误，无法完成请求

学习写作的最好方法是模仿他人的写作方式；学习编码的最好方法是模仿他人的编码方式。

2. httpd代码

httpd是一个多线程的HTTP服务器库，我们可以从中学习报文的处理。

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#define ISspace(x) isspace((int)(x))

#define SERVER_STRING "Server: httpd/0.1.0\r\n"

// 接受请求,并处理

void accept_request(int clientsockfd);

// 无法处理请求,回写400到client

void bad_request(int);

// 将文件内容发送到client

void cat(int client, FILE* fp);

// 输出错误信息

void error_die(const char *);

// 从fd中读取一行,并将读取的'\r\n'和'\r'转换为'\n'

int get_line(int fd, char* buf, int bufsize);

// 返回200 OK给客户端

void headers(int clientsockfd, const char * filename);

// 返回404状态给客户端

void not_found(int);

// 处理客户端文件请求,发送404或200+文件内容到client

void serve_file(int client, const char* filename);

// 开启soket监听

int startup(u_short *);

// 返回501状态给客户端

void unimplemented(int);

/**********************************************************************/

/* A request has caused a call to accept() on the server port to

* return. Process the request appropriately.

* Parameters: the socket connected to the client */

/**********************************************************************/

void accept_request(int client)

{

char buf[1024];

int numchars;

char method[255]; // 方法(请求类型)

char url[255]; // 请求的资源URL

char path[512]; // 请求资源的本地路径

size_t i, j;

struct stat st;

printf("accept\n");

char *query_string = NULL;

// 1. 从客户端连接请求数据包中读取一行

numchars = get_line(client, buf, sizeof(buf));

// 2. 从读取的数据中提取出请求类型

i = 0; j = 0;

while (!ISspace(buf[j]) && (i < sizeof(method) - 1)){

method[i] = buf[j];

i++; j++;

}

method[i] = '\0';

// 3. 判断请求类型

if (strcasecmp(method, "GET") && strcasecmp(method, "POST"))

{

unimplemented(client); // 不支持请求类型,向客户端返回501

return;

}

// 4. 提取请求的资源URL

i = 0;

while (ISspace(buf[j]) && (j < sizeof(buf))){

j++; // 定位下一个非空格位置

}

while (!ISspace(buf[j]) && (i < sizeof(url) - 1) && (j < sizeof(buf)))

{

url[i] = buf[j];

i++; j++;

}

url[i] = '\0';

// 5. 生成本地路径

sprintf(path, "./%s", url);

if (path[strlen(path) - 1] == '/'){

strcat(path, "index.html"); //如果请求url是以'/'结尾,则指定为该目录下的index.html文件

}

// 6. 判断请求资源的状态

if (stat(path, &st) == -1) {

// 从client中读取,直到遇到两个换行(起始行startline和首部header之间间隔)

while ((numchars > 0) && strcmp("\n", buf)){ /* read & discard headers */

numchars = get_line(client, buf, sizeof(buf));

}

not_found(client); // 501

}

else

{

// 请求的是个目录,指定为该目录下的index.html文件

if ((st.st_mode & S_IFMT) == S_IFDIR){

strcat(path, "/index.html");

}

// 返回一个文件内容给客户端

serve_file(client, path); //

}

close(client);

}

/**********************************************************************/

/* Inform the client that a request it has made has a problem.

* Parameters: client socket */

/**********************************************************************/

void bad_request(int client)

{

char buf[1024];

// 向client回写400状态

sprintf(buf, "HTTP/1.0 400 BAD REQUEST\r\n");

send(client, buf, sizeof(buf), 0);

sprintf(buf, "Content-type: text/html\r\n");

send(client, buf, sizeof(buf), 0);

sprintf(buf, "\r\n");

send(client, buf, sizeof(buf), 0);

sprintf(buf, "

Your browser sent a bad request, ");

send(client, buf, sizeof(buf), 0);

sprintf(buf, "such as a POST without a Content-Length.\r\n");

send(client, buf, sizeof(buf), 0);

}

/**********************************************************************/

/* Put the entire contents of a file out on a socket. This function

* is named after the UNIX "cat" command, because it might have been

* easier just to do something like pipe, fork, and exec("cat").

* Parameters: the client socket descriptor

* FILE pointer for the file to cat */

/**********************************************************************/

void cat(int client, FILE *resource)

{

char buf[1024];

// 从resource中读取一行

fgets(buf, sizeof(buf), resource);

// 将文件中的内容发送到客户端

while (!feof(resource))

{

send(client, buf, strlen(buf), 0);

fgets(buf, sizeof(buf), resource);

}

}

/**********************************************************************/

/* Print out an error message with perror() (for system errors; based

* on value of errno, which indicates system call errors) and exit the

* program indicating an error. */

/**********************************************************************/

void error_die(const char *sc)

{

perror(sc); // 输出错误信息

exit(1); // 退出程序

}

/**********************************************************************/

/* Get a line from a socket, whether the line ends in a newline,

* carriage return, or a CRLF combination. Terminates the string read

* with a null character. If no newline indicator is found before the

* end of the buffer, the string is terminated with a null. If any of

* the above three line terminators is read, the last character of the

* string will be a linefeed and the string will be terminated with a

* null character.

* Parameters: the socket descriptor

* the buffer to save the data in

* the size of the buffer

* Returns: the number of bytes stored (excluding null) */

/**********************************************************************/

int get_line(int sock, char *buf, int size)

{

int i = 0;

char c = '\0';

int n;

while ((i < size - 1) && (c != '\n'))

{

// 从sock中读取一个字节

n = recv(sock, &c, 1, 0);

/* DEBUG printf("%02X\n", c); */

if (n > 0)

{

// 将 \r\n 或 \r 转换为'\n'

if (c == '\r')

{

// 读到了'\r'就再预读一个字节

n = recv(sock, &c, 1, MSG_PEEK);

/* DEBUG printf("%02X\n", c); */

// 如果读取到的是'\n',就读取,否则c='\n'

if ((n > 0) && (c == '\n'))

recv(sock, &c, 1, 0);

else

c = '\n';

}

// 读取数据放入buf

buf[i] = c;

i++;

}

else{

c = '\n';

}

}

buf[i] = '\0';

// 返回写入buf的字节数

return(i);

}

/**********************************************************************/

/* Return the informational HTTP headers about a file. */

/* Parameters: the socket to print the headers on

* the name of the file */

/**********************************************************************/

void headers(int client, const char *filename)

{

char buf[1024];

(void)filename; /* could use filename to determine file type */

// 向客户端回写200应答

strcpy(buf, "HTTP/1.0 200 OK\r\n");

send(client, buf, strlen(buf), 0);

strcpy(buf, SERVER_STRING);

send(client, buf, strlen(buf), 0);

sprintf(buf, "Content-Type: text/html\r\n");

send(client, buf, strlen(buf), 0);

strcpy(buf, "\r\n");

send(client, buf, strlen(buf), 0);

}

/**********************************************************************/

/* Give a client a 404 not found status message. */

/**********************************************************************/

void not_found(int client)

{

char buf[1024];

// 向client回写404状态

sprintf(buf, "HTTP/1.0 404 NOT FOUND\r\n");

send(client, buf, strlen(buf), 0);

sprintf(buf, SERVER_STRING);

send(client, buf, strlen(buf), 0);

sprintf(buf, "Content-Type: text/html\r\n");

send(client, buf, strlen(buf), 0);

sprintf(buf, "\r\n");

send(client, buf, strlen(buf), 0);

sprintf(buf, "

Not Found\r\n");

send(client, buf, strlen(buf), 0);

sprintf(buf, "

The server could not fulfill\r\n");

send(client, buf, strlen(buf), 0);

sprintf(buf, "your request because the resource specified\r\n");

send(client, buf, strlen(buf), 0);

sprintf(buf, "is unavailable or nonexistent.\r\n");

send(client, buf, strlen(buf), 0);

sprintf(buf, "\r\n");

send(client, buf, strlen(buf), 0);

}

/**********************************************************************/

/* Send a regular file to the client. Use headers, and report

* errors to client if they occur.

* Parameters: a pointer to a file structure produced from the socket

* file descriptor

* the name of the file to serve */

/**********************************************************************/

void serve_file(int client, const char *filename)

{

FILE *resource = NULL;

int numchars = 1;

char buf[1024];

buf[0] = 'A'; buf[1] = '\0';

// 从client中读取,直到遇到两个换行(起始行start line和首部header的间隔)

while ((numchars > 0) && strcmp("\n", buf)){ /* read & discard headers */

numchars = get_line(client, buf, sizeof(buf));

}

//

resource = fopen(filename, "r");

if (resource == NULL)

not_found(client); // 404错误

else

{

headers(client, filename); // 向客户端回写200 OK

cat(client, resource); // 将resource指向文件中的内容写入client

}

fclose(resource);

}

/**********************************************************************/

/* This function starts the process of listening for web connections

* on a specified port. If the port is 0, then dynamically allocate a

* port and modify the original port variable to reflect the actual

* port.

* Parameters: pointer to variable containing the port to connect on

* Returns: the socket */

/**********************************************************************/

int startup(u_short *port)

{

int httpd = 0;

struct sockaddr_in name;

// 创建一个socket

httpd = socket(PF_INET, SOCK_STREAM, 0);

if (httpd == -1){

error_die("socket");

}

// 填写绑定地址

memset(&name, 0, sizeof(name));

name.sin_family = AF_INET;

name.sin_port = htons(*port);

name.sin_addr.s_addr = htonl(INADDR_ANY);

// 绑定socket到指定地址

if (bind(httpd, (struct sockaddr *)&name, sizeof(name)) < 0){

error_die("bind");

}

// 如果采用随机分配端口,获取它

if (*port == 0) /* if dynamically allocating a port */

{

socklen_t namelen = sizeof(name);

if (getsockname(httpd, (struct sockaddr *)&name, &namelen) == -1)

error_die("getsockname");

*port = ntohs(name.sin_port);

}

// 监听,等待连接

if (listen(httpd, 5) < 0)

error_die("listen");

// 返回正在监听的文件描述符

return(httpd);

}

/**********************************************************************/

/* Inform the client that the requested web method has not been

* implemented.

* Parameter: the client socket */

/**********************************************************************/

void unimplemented(int client)

{

char buf[1024];

// 向client回写501状态

sprintf(buf, "HTTP/1.0 501 Method Not Implemented\r\n");

send(client, buf, strlen(buf), 0);

sprintf(buf, SERVER_STRING);

send(client, buf, strlen(buf), 0);

sprintf(buf, "Content-Type: text/html\r\n");

send(client, buf, strlen(buf), 0);

sprintf(buf, "\r\n");

send(client, buf, strlen(buf), 0);

sprintf(buf, "

Method Not Implemented\r\n");

send(client, buf, strlen(buf), 0);

sprintf(buf, "

\r\n");

send(client, buf, strlen(buf), 0);

sprintf(buf, "

HTTP request method not supported.\r\n");

send(client, buf, strlen(buf), 0);

sprintf(buf, "\r\n");

send(client, buf, strlen(buf), 0);

}

/**********************************************************************/

int main(void)

{

int server_sock = -1;

u_short port = 0; // 使用随机端口

int client_sock = -1;

struct sockaddr_in client_name;

socklen_t client_name_len = sizeof(client_name);

pthread_t newthread;

// 启动服务,监听,等待连接

server_sock = startup(&port);

printf("httpd running on port %d\n", port);

while (1)

{

// 接受请求

client_sock = accept(server_sock,

(struct sockaddr *)&client_name,

&client_name_len);

if (client_sock == -1)

error_die("accept");

// 创建一个线程来处理请求

/* accept_request(client_sock); */

if (pthread_create(&newthread , NULL, reinterpret_cast(accept_request), reinterpret_cast(client_sock)) != 0)

perror("pthread_create");

}

// 关闭

close(server_sock);

return(0);

}