HTTP服务器的本质:tinyhttpd源码分析及拓展

Request Line<CRLF>
Header-Name: header-value<CRLF>
Header-Name: header-value<CRLF>
//一个或多个，均以<CRLF>结尾
<CRLF>
body//请求正文

Method Request-URI HTTP-Version CRLF

GET /form.html HTTP/1.1 (CRLF)

POST /reg.jsp HTTP/ (CRLF)
Accept:image/gif,image/x-xbit,... (CRLF)
...
HOST:www.guet.edu.cn (CRLF)
Content-Length:22 (CRLF)
Connection:Keep-Alive (CRLF)
Cache-Control:no-cache (CRLF)
(CRLF)         //该CRLF表示消息报头已经结束，在此之前为消息报头
user=jeffrey&pwd=1234  //此行以下为提交的数据

void accept_request(int);//处理从套接字上监听到的一个 HTTP 请求
void bad_request(int);//返回给客户端这是个错误请求，400响应码
void cat(int, FILE *);//读取服务器上某个文件写到 socket 套接字
void cannot_execute(int);//处理发生在执行 cgi 程序时出现的错误
void error_die(const char *);//把错误信息写到 perror 
void execute_cgi(int, const char *, const char *, const char *);//运行cgi脚本，这个非常重要，涉及动态解析
int get_line(int, char *, int);//读取一行HTTP报文
void headers(int, const char *);//返回HTTP响应头
void not_found(int);//返回找不到请求文件
void serve_file(int, const char *);//调用 cat 把服务器文件内容返回给浏览器。
int startup(u_short *);//开启http服务，包括绑定端口，监听，开启线程处理链接
void unimplemented(int);//返回给浏览器表明收到的 HTTP 请求所用的 method 不被支持。

/* 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>

#define ISspace(x) isspace((int)(x))
//函数说明：检查参数c是否为空格字符，
//也就是判断是否为空格(‘ ‘)、定位字符(‘ \t ‘)、CR(‘ \r ‘)、换行(‘ \n ‘)、垂直定位字符(‘ \v ‘)或翻页(‘ \f ‘)的情况。
//返回值：若参数c 为空白字符，则返回非 0，否则返回 0。


#define SERVER_STRING "Server: jdbhttpd/0.1.0\r\n"//定义server名称

void accept_request(int);//接收请求

void bad_request(int);//无效请求
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 */
/**********************************************************************/
//接收客户端的连接，并读取请求数据
void accept_request(int client)
{
 char buf[1024];
 int numchars;
 char method[255];
 char url[255];
 char path[512];
 size_t i, j;
 struct stat st;
 int cgi = 0;      /* becomes true if server decides this is a CGI
                    * program */
 char *query_string = NULL;
//获取一行HTTP报文数据
 numchars = get_line(client, buf, sizeof(buf));
 //
 i = 0; j = 0;
 //对于HTTP报文来说，第一行的内容即为报文的起始行，格式为<method> <request-URL> <version>，
 //每个字段用空白字符相连
 while (!ISspace(buf[j]) && (i < sizeof(method) - 1))
 {
 //提取其中的请求方式是GET还是POST
  method[i] = buf[j];
  i++; j++;
 }
 method[i] = ‘\0‘;
//函数说明：strcasecmp()用来比较参数s1 和s2 字符串，比较时会自动忽略大小写的差异。
//返回值：若参数s1 和s2 字符串相同则返回0。s1 长度大于s2 长度则返回大于0 的值，s1 长度若小于s2 长度则返回小于0 的值。
 if (strcasecmp(method, "GET") && strcasecmp(method, "POST"))
 {
 //tinyhttp仅仅实现了GET和POST
  unimplemented(client);
  return;
 }
//cgi为标志位，置1说明开启cgi解析
 if (strcasecmp(method, "POST") == 0)
//如果请求方法为POST，需要cgi解析
  cgi = 1;

 i = 0;
 //将method后面的后边的空白字符略过
 while (ISspace(buf[j]) && (j < sizeof(buf)))
  j++;
 //继续读取request-URL
 while (!ISspace(buf[j]) && (i < sizeof(url) - 1) && (j < sizeof(buf)))
 {
  url[i] = buf[j];
  i++; j++;
 }
 url[i] = ‘\0‘;
//如果是GET请求，url可能会带有?,有查询参数
 if (strcasecmp(method, "GET") == 0)
 {
  query_string = url;
  while ((*query_string != ‘?‘) && (*query_string != ‘\0‘))
   query_string++;
  if (*query_string == ‘?‘)
  {
  //如果带有查询参数，需要执行cgi，解析参数，设置标志位为1
   cgi = 1;
  //将解析参数截取下来
   *query_string = ‘\0‘;
   query_string++;
  }
 }
//以上已经将起始行解析完毕
//url中的路径格式化到path
 sprintf(path, "htdocs%s", url);
//学习到这里明天继续TODO
//如果path只是一个目录，默认设置为首页index.html
 if (path[strlen(path) - 1] == ‘/‘)
  strcat(path, "index.html");
 
 //函数定义:    int stat(const char *file_name, struct stat *buf); 
 //函数说明:    通过文件名filename获取文件信息，并保存在buf所指的结构体stat中 
 //返回值:     执行成功则返回0，失败返回-1，错误代码存于errno（需要include <errno.h>）
 if (stat(path, &st) == -1) {
 //假如访问的网页不存在，则不断的读取剩下的请求头信息，并丢弃即可
  while ((numchars > 0) && strcmp("\n", buf))  /* read & discard headers */
   numchars = get_line(client, buf, sizeof(buf));
  //最后声明网页不存在
  not_found(client);
 }
 else
 {
 //如果访问的网页存在则进行处理
  if ((st.st_mode & S_IFMT) == S_IFDIR)//S_IFDIR代表目录
 //如果路径是个目录，那就将主页进行显示
   strcat(path, "/index.html");
  if ((st.st_mode & S_IXUSR) ||
      (st.st_mode & S_IXGRP) ||
      (st.st_mode & S_IXOTH)    )
      //S_IXUSR:文件所有者具可执行权限
      //S_IXGRP:用户组具可执行权限
      //S_IXOTH:其他用户具可读取权限  
   cgi = 1;
  if (!cgi)
  //将静态文件返回
   serve_file(client, path);
  else
  //执行cgi动态解析
   execute_cgi(client, path, method, query_string);
  
 }

 close(client);//因为http是面向无连接的，所以要关闭
}

/**********************************************************************/
/* Inform the client that a request it has made has a problem.
 * Parameters: client socket */
/**********************************************************************/
void bad_request(int client)
{
 char buf[1024];
//发送400
 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)
{
//发送文件的内容
 char buf[1024];
//读取文件到buf中
 fgets(buf, sizeof(buf), resource);
 while (!feof(resource))//判断文件是否读取到末尾
 {
 //读取并发送文件内容
  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];
//发送500
 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 */
/**********************************************************************/
//执行cgi动态解析
void execute_cgi(int client, const char *path,
                 const char *method, const char *query_string)
{
 char buf[1024];
 int cgi_output[2];//声明的读写管道，切莫被名称给忽悠，会给出图进行说明
 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‘;
 if (strcasecmp(method, "GET") == 0)
 //如果是GET请求
 //读取并且丢弃头信息
  while ((numchars > 0) && strcmp("\n", buf)) 
   numchars = get_line(client, buf, sizeof(buf));
 else    
 {
 //处理的请求为POST
  numchars = get_line(client, buf, sizeof(buf));
  while ((numchars > 0) && strcmp("\n", buf))
  {//循环读取头信息找到Content-Length字段的值
   buf[15] = ‘\0‘;//目的是为了截取Content-Length:
   
   if (strcasecmp(buf, "Content-Length:") == 0)
   	//"Content-Length: 15"
    content_length = atoi(&(buf[16]));//获取Content-Length的值
   numchars = get_line(client, buf, sizeof(buf));
  }
  if (content_length == -1) {
  //错误请求
   bad_request(client);
   return;
  }
 }
//返回正确响应码200
 sprintf(buf, "HTTP/1.0 200 OK\r\n");
 send(client, buf, strlen(buf), 0);
//#include<unistd.h>
//int pipe(int filedes[2]);
//返回值：成功，返回0，否则返回-1。参数数组包含pipe使用的两个文件的描述符。fd[0]:读管道，fd[1]:写管道。
//必须在fork()中调用pipe()，否则子进程不会继承文件描述符。
//两个进程不共享祖先进程，就不能使用pipe。但是可以使用命名管道。
//pipe(cgi_output)执行成功后，cgi_output[0]:读通道 cgi_output[1]:写通道，这就是为什么说不要被名称所迷惑
 if (pipe(cgi_output) < 0) {
  cannot_execute(client);
  return;
 }
 if (pipe(cgi_input) < 0) {
  cannot_execute(client);
  return;
 }

 if ( (pid = fork()) < 0 ) {
  cannot_execute(client);
  return;
 }
 //fork出一个子进程运行cgi脚本
 if (pid == 0)  /* 子进程: 运行CGI 脚本 */
 {
  char meth_env[255];
  char query_env[255];
  char length_env[255];

  dup2(cgi_output[1], 1);//1代表着stdout，0代表着stdin，将系统标准输出重定向为cgi_output[1]
  dup2(cgi_input[0], 0);//将系统标准输入重定向为cgi_input[0]，这一点非常关键，
  						//cgi程序中用的是标准输入输出进行交互
  close(cgi_output[0]);//关闭了cgi_output中的读通道
  close(cgi_input[1]);//关闭了cgi_input中的写通道
  //CGI标准需要将请求的方法存储环境变量中，然后和cgi脚本进行交互
  //存储REQUEST_METHOD
  sprintf(meth_env, "REQUEST_METHOD=%s", method);
  putenv(meth_env);
  if (strcasecmp(method, "GET") == 0) {
  //存储QUERY_STRING
   sprintf(query_env, "QUERY_STRING=%s", query_string);
   putenv(query_env);
  }
  else {   /* POST */
  	//存储CONTENT_LENGTH
   sprintf(length_env, "CONTENT_LENGTH=%d", content_length);
   putenv(length_env);
  }
 // 表头文件#include<unistd.h>
 // 定义函数
 // int execl(const char * path,const char * arg,....);
 // 函数说明
 // execl()用来执行参数path字符串所代表的文件路径，接下来的参数代表执行该文件时传递过去的argv(0)、argv[1]……，最后一个参数必须用空指针(NULL)作结束。
 // 返回值
 // 如果执行成功则函数不会返回，执行失败则直接返回-1，失败原因存于errno中。
  execl(path, path, NULL);//执行CGI脚本
  exit(0);
 } else {    /* 父进程 */
  close(cgi_output[1]);//关闭了cgi_output中的写通道，注意这是父进程中cgi_output变量和子进程要区分开
  close(cgi_input[0]);//关闭了cgi_input中的读通道
  if (strcasecmp(method, "POST") == 0)
   for (i = 0; i < content_length; i++) {
   	//开始读取POST中的内容
    recv(client, &c, 1, 0);
	//将数据发送给cgi脚本
    write(cgi_input[1], &c, 1);
   }
   //读取cgi脚本返回数据
  while (read(cgi_output[0], &c, 1) > 0)
  	//发送给浏览器
   send(client, &c, 1, 0);
//运行结束关闭
  close(cgi_output[0]);
  close(cgi_input[1]);
//定义函数：pid_t waitpid(pid_t pid, int * status, int options);
//函数说明：waitpid()会暂时停止目前进程的执行, 直到有信号来到或子进程结束. 
//如果在调用wait()时子进程已经结束, 则wait()会立即返回子进程结束状态值. 子进程的结束状态值会由参数status 返回, 
//而子进程的进程识别码也会一快返回. 
//如果不在意结束状态值, 则参数status 可以设成NULL. 参数pid 为欲等待的子进程识别码, 其他数值意义如下：
//1、pid<-1 等待进程组识别码为pid 绝对值的任何子进程.
//2、pid=-1 等待任何子进程, 相当于wait().
//3、pid=0 等待进程组识别码与目前进程相同的任何子进程.
//4、pid>0 等待任何子进程识别码为pid 的子进程.
  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) */
/**********************************************************************/
//解析一行http报文
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 */
/**********************************************************************/
void headers(int client, const char *filename)
{
 char buf[1024];
 (void)filename;  /* could use filename to determine file type */
//发送HTTP头
 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];
 //返回404
 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 */
/**********************************************************************/
//将请求的文件发送回浏览器客户端
void serve_file(int client, const char *filename)
{
 FILE *resource = NULL;
 int numchars = 1;
 char buf[1024];

 buf[0] = ‘A‘; buf[1] = ‘\0‘;//这个赋值不清楚是干什么的
 while ((numchars > 0) && strcmp("\n", buf)) //将HTTP请求头读取并丢弃
  numchars = get_line(client, buf, sizeof(buf));
//打开文件
 resource = fopen(filename, "r");
 if (resource == NULL)
 //如果文件不存在，则返回not_found
  not_found(client);
 else
 {
 //添加HTTP头
  headers(client, filename);
 //并发送文件内容
  cat(client, resource);
 }
 fclose(resource);//关闭文件句柄
}

/**********************************************************************/
/* 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 */
/**********************************************************************/
//启动服务端
int startup(u_short *port)
{
 int httpd = 0;
 struct sockaddr_in name;
//设置http socket
 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);
 //绑定端口
 if (bind(httpd, (struct sockaddr *)&name, sizeof(name)) < 0)
  error_die("bind");
 if (*port == 0)  /*动态分配一个端口 */
 {
  int namelen = sizeof(name);
  if (getsockname(httpd, (struct sockaddr *)&name, &namelen) == -1)
   error_die("getsockname");
  *port = ntohs(name.sin_port);
 }
 //监听连接
 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];
//发送501说明相应方法没有实现
 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, "<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>HTTP request method not supported.\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;
 u_short port = 0;
 int client_sock = -1;
 struct sockaddr_in client_name;
 int client_name_len = sizeof(client_name);
 pthread_t newthread;
//启动server socket
 server_sock = startup(&port);
 
 printf("httpd running on port %d\n", port);

 while (1)
 {
 //接受客户端连接
  client_sock = accept(server_sock,
                       (struct sockaddr *)&client_name,
                       &client_name_len);
  if (client_sock == -1)
   error_die("accept");
 /*启动线程处理新的连接 */
 if (pthread_create(&newthread , NULL, accept_request, client_sock) != 0)
   perror("pthread_create");
 }
//关闭server socket
 close(server_sock);

 return(0);
}

#!/usr/bin/perl -Tw

use strict;
use CGI;

my($cgi) = new CGI;

print $cgi->header;
my($color) = "blue";
$color = $cgi->param(‘color‘) if defined $cgi->param(‘color‘);

print $cgi->start_html(-title => uc($color),
                       -BGCOLOR => $color);
print $cgi->h1("This is $color");
print $cgi->end_html;

<html>
	<head>
		<title>注册信息</title>
		<meta charset="utf-8">
	</head>
	<body>
		<form action="register.cgi" method="POST">
			账号：<input type="text" name="zhanghao" value="" size="10" maxlength="5">
			<br>
			<br>
			密码：<input type="password" value="" name="mima" size="10">
			<br>
			<br>
			<input type="hidden" value="隐藏的内容" name="mihiddenma" size="10">
			
			爱好：<input type="checkbox" name="tiyu" checked="checked">体育<input type="checkbox" name="changge">唱歌
			<br>
			<br>
			性别：<input type="radio" name="sex" checked="checked">男<input type="radio" name="sex">女
			<br>
			<br>
			自我介绍：<br>
			<textarea cols="35" rows="10" name="ziwojieshao">
				这里是自我介绍
			</textarea>
			<br>
			<br>
			地址：
			<select name="dizhi">
				<option value="sichuan">四川</option>
				<option value="beijing">北京</option>
				<option value="shanghai">上海</option>
			</select>
			<br>
			<br>
			<input type="submit" value="提交">
			<input type="reset" value="重置">
		</form>
	</body>
</html>

#!/usr/bin/python
#coding:utf-8
import sys,os
length = os.getenv(‘CONTENT_LENGTH‘)

if length:
    postdata = sys.stdin.read(int(length))
    print "Content-type:text/html\n"
    print ‘<html>‘ 
    print ‘<head>‘ 
    print ‘<title>POST</title>‘ 
    print ‘</head>‘ 
    print ‘<body>‘ 
    print ‘<h2> POST data </h2>‘
    print ‘<ul>‘
    for data in postdata.split(‘&‘):
    	print  ‘<li>‘+data+‘</li>‘
    print ‘</ul>‘
    print ‘</body>‘
    print ‘</html>‘
    
else:
    print "Content-type:text/html\n"
    print ‘no found‘