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);
}