协议-tinyhttpd
一个非常轻量的httpd服务器，只有500行代码。
我后边用python写了一个很简陋的几十行代码的，可以看下那个来简单看一下。
这里只看了网络编程的一些东西，进程通信挖个坑，下次填。
很适合
https://github.com/EZLippi/Tinyhttpd.git
编译方式是直接make
编译执行后发现开启4000端口
默认加载htdocs下的index.html
当去访问一个不存在的文件a.html
cgi问题
这里写一个简单的shell cgi来替代自带的cgi
#!/bin/bash
echo "Content-Type: text/html"
echo
echo "<HTML><BODY>"
echo "<CENTER>Today is:</CENTER>"
echo "<CENTER><B>"
date
echo "</B></CENTER>"
echo "</BODY></HTML>"访问cgi文件，发现cgi并未被执行
是因为没有执行权限，所以导致直接被当成静态文件，而有执行权限的话，静态文件也会被当作cgi执行。
尝试将所有的文件赋予权限
chmod 777 ./*
index页面无法正常显示
执行方式可以通过下图来理解
注释代码
项目放代码阅读时的代码放gitee了需要可自行下载：https://gitee.com/p1piyang/backward-analysis/
/* J. David's webserver */
/* This is a simple webserver.
* Created November 1999 by J. David Blackstone.
* CSE 4344 (Network concepts), Prof. Zeigler
* University of Texas at Arlington
*/
/* This program compiles for Sparc Solaris 2.6.
* To compile for Linux:
* 1) Comment out the #include <pthread.h> line.
* 2) Comment out the line that defines the variable newthread.
* 3) Comment out the two lines that run pthread_create().
* 4) Uncomment the line that runs accept_request().
* 5) Remove -lsocket from the Makefile.
*/
#include <stdio.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <ctype.h>
#include <strings.h>
#include <string.h>
#include <sys/stat.h>
#include <pthread.h>
#include <sys/wait.h>
#include <stdlib.h>
#include <stdint.h>
#define ISspace(x) isspace((int)(x))
#define SERVER_STRING "Server: jdbhttpd/0.1.0\r\n"
#define STDIN 0
#define STDOUT 1
#define STDERR 2
void accept_request(void *);
void bad_request(int);
void cat(int, FILE *);
void cannot_execute(int);
void error_die(const char *);
void execute_cgi(int, const char *, const char *, const char *);
int get_line(int, char *, int);
void headers(int, const char *);
void not_found(int);
void serve_file(int, const char *);
int startup(u_short *);
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(void *arg)
{
int client = (intptr_t)arg;
char buf[1024];
size_t numchars;
char method[255];
char url[255];
char path[512];
size_t i, j;
struct stat st; //文件信息
//struct stat{
// dev_t st_dev; /* ID of device containing file */文件使用的设备号
// ino_t st_ino; /* inode number */ 索引节点号
// mode_t st_mode; /* protection */ 文件对应的模式，文件，目录等
// nlink_t st_nlink; /* number of hard links */ 文件的硬连接数
// uid_t st_uid; /* user ID of owner */ 所有者用户识别号
// gid_t st_gid; /* group ID of owner */ 组识别号
// dev_t st_rdev; /* device ID (if special file) */ 设备文件的设备号
// off_t st_size; /* total size, in bytes */ 以字节为单位的文件容量
// blksize_t st_blksize; /* blocksize for file system I/O */ 包含该文件的磁盘块的大小
// blkcnt_t st_blocks; /* number of 512B blocks allocated */ 该文件所占的磁盘块
// time_t st_atime; /* time of last access */ 最后一次访问该文件的时间
// time_t st_mtime; /* time of last modification */ /最后一次修改该文件的时间
// time_t st_ctime; /* time of last status change */ 最后一次改变该文件状态的时间
//};
int cgi = 0; /* becomes true if server decides this is a CGI
* program */
char *query_string = NULL;
//读取http请求的第一行数据
numchars = get_line(client, buf, sizeof(buf));
i = 0; j = 0;
//吧请求方法存到，，method中
while (!ISspace(buf[i]) && (i < sizeof(method) - 1))
{
method[i] = buf[i];
i++;
}
j=i;
method[i] = '\0';
//判断如果不是get或者post方法，发送response给客户端表示无法实现
if (strcasecmp(method, "GET") && strcasecmp(method, "POST"))
{
//使用sprintf函数将要返回的内容给buf,使用send函数返回给client
unimplemented(client);
return;
}
//判断为post方法
if (strcasecmp(method, "POST") == 0)
cgi = 1;
i = 0;
//跳过空格
while (ISspace(buf[j]) && (j < numchars))
j++;
//获取url
while (!ISspace(buf[j]) && (i < sizeof(url) - 1) && (j < numchars))
{
url[i] = buf[j];
i++; j++;
}
url[i] = '\0';
//get方法
if (strcasecmp(method, "GET") == 0)
{
query_string = url;
//用于记录带参数的GET方法请求中 ‘？’后的参数
while ((*query_string != '?') && (*query_string != '\0'))
query_string++;
if (*query_string == '?')
{
cgi = 1;
*query_string = '\0';
query_string++;
}
}
//将htdocs与url拼接到一起给path，即我们的资源文件都在htdocs下
sprintf(path, "htdocs%s", url);
//判断如果URL的最后一位是‘/’，加上index.html
if (path[strlen(path) - 1] == '/')
strcat(path, "index.html");
//定义函数：int stat(const char * file_name, struct stat *buf);
//函数说明：stat()用来将参数file_name 所指的文件状态, 复制到参数buf 所指的结构中。
//返回值：执行成功则返回0，失败返回-1，错误代码存于errno。
//这里改了一下，把东西处理下可以看到是处理包头。
//根据执行来看，这个if判断
if (stat(path, &st) == -1) {
while ((numchars > 0) && strcmp("\n", buf)) /* read & discard headers */
{
numchars = get_line(client, buf, sizeof(buf));
char *test = buf;
printf("for: %s", test);
}
//打印404返回页面
not_found(client);
}
else
{
// 文件存在，那则跟常量S_IFMT相与，相与之后的值可以用来判断该文件是什么类型的
// 此处与上边判断路径是不是以 \ 结尾的地方作用一样，可以省略，留着可重复确认。
if ((st.st_mode & S_IFMT) == S_IFDIR)
strcat(path, "/index.html");
//判断权限的，前面有说过的
if ((st.st_mode & S_IXUSR) ||
(st.st_mode & S_IXGRP) ||
(st.st_mode & S_IXOTH) )
cgi = 1;
if (!cgi)
{
printf("nocgi\n");
//不需要cgi的
serve_file(client, path);
}
else
{
//需要cgi的
printf("cgi\n");
execute_cgi(client, path, method, query_string);
}
}
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];
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, "<P>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];
//读取文件内容，发送到前端。
fgets(buf, sizeof(buf), resource);
while (!feof(resource))
{
send(client, buf, strlen(buf), 0);
fgets(buf, sizeof(buf), resource);
}
}
/**********************************************************************/
/* Inform the client that a CGI script could not be executed.
* Parameter: the client socket descriptor. */
/**********************************************************************/
void cannot_execute(int client)
{
char buf[1024];
sprintf(buf, "HTTP/1.0 500 Internal Server Error\r\n");
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, "<P>Error prohibited CGI execution.\r\n");
send(client, buf, strlen(buf), 0);
}
/**********************************************************************/
/* 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);
exit(1);
}
/**********************************************************************/
/* Execute a CGI script. Will need to set environment variables as
* appropriate.
* Parameters: client socket descriptor
* path to the CGI script */
/**********************************************************************/
// cgi用于动态网页的处理
// execute_cgi函数创建了两个进程，子进程用于cgi文件的处理，父进程用于往socket读写数据
void execute_cgi(int client, const char *path,
const char *method, const char *query_string)
{
char buf[1024];
int cgi_output[2];
int cgi_input[2];
pid_t pid;
int status;
int i;
char c;
int numchars = 1;
int content_length = -1;
buf[0] = 'A'; buf[1] = '\0';
printf(">exec cgi\n");
//get方法
if (strcasecmp(method, "GET") == 0)
while ((numchars > 0) && strcmp("\n", buf)) /* read & discard headers */
{
printf(">get\n");
numchars = get_line(client, buf, sizeof(buf));
}
//post方法
else if (strcasecmp(method, "POST") == 0) /*POST*/
{
numchars = get_line(client, buf, sizeof(buf));
while ((numchars > 0) && strcmp("\n", buf))
{
// "Content-Length:"长度为15个字符，所以将前15个字符比较。
buf[15] = '\0';
// 如果是Content-Length，读取这个改字段转为整数
if (strcasecmp(buf, "Content-Length:") == 0)
{
content_length = atoi(&(buf[16]));
printf("lenght:%d\n",content_length);
}
numchars = get_line(client, buf, sizeof(buf));
}
//无法处理的话，400错误
if (content_length == -1) {
bad_request(client);
return;
}
}
else/*HEAD or other*/
{
}
//创建管道
//子进程写管道
if (pipe(cgi_output) < 0) {
//服务错误500
cannot_execute(client);
return;
}
//子进程写管道
if (pipe(cgi_input) < 0) {
//服务错误500
cannot_execute(client);
return;
}
//创建子进程
if ( (pid = fork()) < 0 ) {
cannot_execute(client);
return;
}
//响应成功
sprintf(buf, "HTTP/1.0 200 OK\r\n");
send(client, buf, strlen(buf), 0);
// 这下面是另一个坑，进程通信。
if (pid == 0) /* child: CGI script */
{
char meth_env[255];
char query_env[255];
char length_env[255];
dup2(cgi_output[1], STDOUT);
dup2(cgi_input[0], STDIN);
close(cgi_output[0]);
close(cgi_input[1]);
sprintf(meth_env, "REQUEST_METHOD=%s", method);
putenv(meth_env);
if (strcasecmp(method, "GET") == 0) {
sprintf(query_env, "QUERY_STRING=%s", query_string);
putenv(query_env);
}
else { /* POST */
sprintf(length_env, "CONTENT_LENGTH=%d", content_length);
putenv(length_env);
}
execl(path, NULL);
exit(0);
} else { /* parent */
close(cgi_output[1]);
close(cgi_input[0]);
if (strcasecmp(method, "POST") == 0)
for (i = 0; i < content_length; i++) {
recv(client, &c, 1, 0);
write(cgi_input[1], &c, 1);
}
while (read(cgi_output[0], &c, 1) > 0)
send(client, &c, 1, 0);
close(cgi_output[0]);
close(cgi_input[1]);
waitpid(pid, &status, 0);
}
}
/**********************************************************************/
/* 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) */
/**********************************************************************/
//处理包，大概流程是循环读取每个字符
//如果回车符(\r)的后面不是换行符(\n)或者读取失败就把当前读取的字符置为换行，从而终止循环
//如果没有成功接收到字符，以 \n 结尾，结束循环
//最后以\n结尾
int get_line(int sock, char *buf, int size)
{
int i = 0;
char c = '\0';
int n;
//
while ((i < size - 1) && (c != '\n'))
{
n = recv(sock, &c, 1, 0);
/* DEBUG printf("%02X\n", c); */
if (n > 0)
{
if (c == '\r')
{
n = recv(sock, &c, 1, MSG_PEEK);
/* DEBUG printf("%02X\n", c); */
if ((n > 0) && (c == '\n'))
recv(sock, &c, 1, 0);
else
c = '\n';
}
buf[i] = c;
i++;
}
else
c = '\n';
}
buf[i] = '\0';
return(i);
}
/**********************************************************************/
/* Return the informational HTTP headers about a file. */
/* Parameters: the socket to print the headers on
* the name of the file */
/**********************************************************************/
//响应头
void headers(int client, const char *filename)
{
char buf[1024];
(void)filename; /* could use filename to determine file type */
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)
{
//将内容打印到缓存，并且发送出去
char buf[1024];
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, "<HTML><TITLE>Not Found</TITLE>\r\n");
send(client, buf, strlen(buf), 0);
sprintf(buf, "<BODY><P>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, "</BODY></HTML>\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';
while ((numchars > 0) && strcmp("\n", buf)) /* read & discard headers */
numchars = get_line(client, buf, sizeof(buf));
//打开文件，判断是否有文件
resource = fopen(filename, "r");
if (resource == NULL)
not_found(client);
else
{
//构造响应头给客户端
headers(client, filename);
//将文件内容发送给客户端
cat(client, resource);
}
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 */
/**********************************************************************/
//初始化 httpd 服务，包括建立套接字，绑定端口，进行监听等。
int startup(u_short *port)
{
int httpd = 0;
int on = 1;
struct sockaddr_in name;
//正常的socket创建流程
httpd = socket(PF_INET, SOCK_STREAM, 0);
if (httpd == -1)
error_die("socket");
memset(&name, 0, sizeof(name));
name.sin_family = AF_INET;
name.sin_port = htons(*port);
name.sin_addr.s_addr = htonl(INADDR_ANY);
//setsockopt()函数，用于任意类型、任意状态套接口的设置选项值
if ((setsockopt(httpd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on))) < 0)
{
error_die("setsockopt failed");
}
//绑定socket到端口，port等于0，系统会随机分配一个端口（bind函数里实现）
if (bind(httpd, (struct sockaddr *)&name, sizeof(name)) < 0)
error_die("bind");
// 这个if的作用是将自动分配的端口传给port
if (*port == 0) /* if dynamically allocating a port */
{
socklen_t namelen = sizeof(name);
// 获取socket绑定的地址信息
if (getsockname(httpd, (struct sockaddr *)&name, &namelen) == -1)
error_die("getsockname");
*port = ntohs(name.sin_port);
}
//监听端口
if (listen(httpd, 5) < 0)
error_die("listen");
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];
sprintf(buf, "HTTP/1.0 501 guan zhu jia ran, dun dun jie chan\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, "<HTML><HEAD><TITLE>Method Not Implemented\r\n");
send(client, buf, strlen(buf), 0);
sprintf(buf, "</TITLE></HEAD>\r\n");
send(client, buf, strlen(buf), 0);
sprintf(buf, "<BODY><P>if you watch this page, please follow JiaRan_Diana.\r\n");
send(client, buf, strlen(buf), 0);
sprintf(buf, "<br/><img src='https://img2.baidu.com/it/u=2323296913,2613522307&fm=253&app=138&size=w931&n=0&f=JPEG&fmt=auto?sec=1658854800&t=7b90c5387e83fb57a89e051eccbb7eb9'>\r\n");
send(client, buf, strlen(buf), 0);
sprintf(buf, "</BODY></HTML>\r\n");
send(client, buf, strlen(buf), 0);
}
/**********************************************************************/
int main(void)
{
int server_sock = -1; //服务端套接字接口
u_short port = 4000; //端口
int client_sock = -1;//已连接套接字描述符，初始化为-1（客户端）
struct sockaddr_in client_name;
socklen_t client_name_len = sizeof(client_name);
pthread_t newthread;
//调用startup()函数，建立一个监听套接字，在对应的端口建立httpd服务
server_sock = startup(&port);
printf("httpd running on port %d\n", port);
//循环调用accept()函数来等待客户端的连接，accept()会议阻塞的方式运行
//有客户端链接后返回到client_sock，去创建新线程处理请求
while (1)
{
client_sock = accept(server_sock, (struct sockaddr *)&client_name, &client_name_len);
if (client_sock == -1)
error_die("accept");
//创建新线程用accept_request()函数处理新请求，同时将客户端socket作为参数传过去
/* accept_request(&client_sock); */
if (pthread_create(&newthread , NULL, (void *)accept_request, (void *)(intptr_t)client_sock) != 0)
perror("pthread_create");
}
close(server_sock);
return(0);
}
协议-tinyhttpd
http://example.com/article/68d281b.html