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A.3  Programmation avec la commande nc

A.3.1  Serveur Web minimal en Bourne Shell

#!/bin/bash
WEB_DIR=`dirname $0`/www/
NOT_FOUND=error.html
read cmd page proto
echo $cmd $page $proto >> /tmp/log
while read line ; do
  echo $line >> /tmp/log
  if [ "$line" = "
" ] ; then break ; fi
done
if [ "$cmd" = GET ] ; then
  path=${WEB_DIR}$page
  code=200
  if [ ! -f "$path" ] ; then
    path=${WEB_DIR}/${NOT_FOUND}
    code=404
  fi
  case `basename $path` in
    *.png) type="image/png";;
    *.html) type="text/html";;
  esac
  size=`cat $path | wc -c`
  echo "HTTP/1.0 $code"
  echo "Server: ShellWeb"
  echo "Content-type: $type"
  echo "Content-length: $size"
  echo
  cat $path
fi

A.3.2  Serveur Web minimal en C

/**** Minimal web server ****/

/** Include files **/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>


/** Some constants **/

#define WEB_DIR  "./www"
#define PAGE_NOTFOUND "error.html"
#define MAX_BUFFER 1024

#define CODE_OK  200
#define CODE_NOTFOUND 404

/** Main procedure **/

int main(void){
char buffer[MAX_BUFFER];
char cmd[MAX_BUFFER];
char page[MAX_BUFFER];
char proto[MAX_BUFFER];
char path[MAX_BUFFER];
char type[MAX_BUFFER];

if(fgets(buffer,MAX_BUFFER,stdin)==NULL) exit(-1);
if(sscanf(buffer,"%s %s %s",cmd,page,proto)!=3) exit(-1);
while(fgets(buffer,MAX_BUFFER,stdin)!=NULL){
  if(strcmp(buffer,"\r\n")==0) break;
  }
if(strcasecmp(cmd,"GET")==0){
  int code=CODE_OK;
  struct stat fstat;
  sprintf(path,"%s%s",WEB_DIR,page);
  if(stat(path,&fstat)!=0 || !S_ISREG(fstat.st_mode)){
    sprintf(path,"%s/%s",WEB_DIR,PAGE_NOTFOUND);
    code=CODE_NOTFOUND;
    }
  strcpy(type,"text/html");
  char *end=page+strlen(page);
  if(strcmp(end-4,".png")==0) strcpy(type,"image/png");
  if(strcmp(end-4,".jpg")==0) strcpy(type,"image/jpg");
  if(strcmp(end-4,".gif")==0) strcpy(type,"image/gif");
  fprintf(stdout,"HTTP/1.0 %d\r\n",code);
  fprintf(stdout,"Server: CWeb\r\n");
  fprintf(stdout,"Content-type: %s\r\n",type);
  fprintf(stdout,"Content-length: %d\r\n",fstat.st_size);
  fprintf(stdout,"\r\n");
  fflush(stdout);
  int fd=open(path,O_RDONLY);
  if(fd>=0){
    int bytes;
    while((bytes=read(fd,buffer,MAX_BUFFER))>0) write(1,buffer,bytes);
    close(fd);
    }
  }
}

A.3.3  Exemple d’utilisation avec nc

while true ; do  nc -l -p 80 -c ./web ; done

A.3.4  Exemple de page HTML

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
<HTML>
  <HEAD>
    <TITLE>Serveur d'enseignement de Polytech'Lille</TITLE>
  </HEAD>
  <BODY>
    <TABLE BORDER=0 WIDTH=100% HEIGHT=100%>
      <TR><TD VALIGN=center>
        <CENTER>
          <IMG ALT="" SRC="elephant.png">
        </CENTER>
      </TD></TR>
    </TABLE>
  </BODY>
</HTML>
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