====== Net 2 ======

<code C>
#include "../common/common.c"

#define NAME "net2"
#define UID 997
#define GID 997
#define PORT 2997

void run()
{
    unsigned int quad[4];
    int i;
    unsigned int result, wanted;

    result = 0;
    for(i = 0; i < 4; i++) {
        quad[i] = random();
        result += quad[i];

        if(write(0, &(quad[i]), sizeof(result)) != sizeof(result)) { 
            errx(1, ":(\n");
        }
    }

    if(read(0, &wanted, sizeof(result)) != sizeof(result)) {
        errx(1, ":<\n");
    }


    if(result == wanted) {
        printf("you added them correctly\n");
    } else {
        printf("sorry, try again. invalid\n");
    }
}

int main(int argc, char **argv, char **envp)
{
    int fd;
    char *username;

    /* Run the process as a daemon */
    background_process(NAME, UID, GID);  

    /* Wait for socket activity and return */
    fd = serve_forever(PORT);

    /* Set the client socket to STDIN, STDOUT, and STDERR */
    set_io(fd);

    /* Don't do this :> */
    srandom(time(NULL));

    run();
}
</code>

Le programme choisis 4 int qu'il nous envois et additionne. Il attends que nous lui donnions le résultat de cette addition. Pour réaliser cela, nous devons utiliser à la fois la fonction ''pack'' et ''unpack''.

<code Python>
#!/usr/bin/env python
# encoding: utf-8

import telnetlib
from struct import unpack, pack

HOST = "192.168.1.29"
PORT = 2997

t = telnetlib.Telnet(HOST, PORT)

chaine =  t.read_some() + t.read_some() + t.read_some() + t.read_some()
print "Chaine : %s" % repr(chaine)
result = unpack('<I', chaine[0:4])[0]
result += unpack('<I', chaine[4:8])[0]
result += unpack('<I', chaine[8:12])[0]
result += unpack('<I', chaine[12:])[0]
result &= 0xffffffff
print "Result : %d" % result
print "Send : %s" % repr(pack('<I',result))
t.write("%s\n" % pack('<I',result))
print t.read_some()

t.close()
</code>