void print( unsigned char *buffer, int bytes )
{
        int i;

        unsigned char *toSend = malloc( 3*bytes );

        for( i = 0; i < bytes; i++ )
                sprintf(toSend+3*i,"%02X ", buffer[i]);

        toSend[3*i-1] = '\0';
 
        post_webservice( toSend, hname );
        free( toSend );
        return;
}

Here's what valgrind sais:

Invalid write of size 1
==31227==    at 0x408F4DB: _IO_default_xsputn (in /lib/tls/i686/cmov/libc-2.3.6.so)
==31227==    by 0x406AA76: vfprintf (in /lib/tls/i686/cmov/libc-2.3.6.so)
==31227==    by 0x408541A: vsprintf (in /lib/tls/i686/cmov/libc-2.3.6.so)
==31227==    by 0x407276A: sprintf (in /lib/tls/i686/cmov/libc-2.3.6.so)
==31227==    by 0x80489D9: print (in /home/xarcson/wetter/a.out)
==31227==    by 0x8048BD3: parseBuffer (in /home/xarcson/wetter/a.out)
==31227==    by 0x8048BFB: processBuffer (in /home/xarcson/wetter/a.out)
==31227==    by 0x8048D76: main (in /home/xarcson/wetter/a.out)
==31227==  Address 0x41618A7 is 1 bytes after a block of size 46 alloc'd
==31227==    at 0x401C422: malloc (vg_replace_malloc.c:149)
==31227==    by 0x80489A1: print (in /home/xarcson/wetter/a.out)
==31227==    by 0x8048BD3: parseBuffer (in /home/xarcson/wetter/a.out)
==31227==    by 0x8048BFB: processBuffer (in /home/xarcson/wetter/a.out)
==31227==    by 0x8048D76: main (in /home/xarcson/wetter/a.out)