Hello everybody,
I'm reading and learning a lot about TCP/IP protocols, and i want to know how to calculate the IP header checksum manually. I've searched for it EVERYWHERE! and none of options work.
I've read a function that does it pretty good, but i can't "translate" it into a human form so i can do it manually.
here's the code:
Code:
unsigned short checksum(unsigned short *ptr, int length){
register int sum = 0;
u_short answer = 0;
register u_short *w = ptr;
register int nleft = len;
while(nleft > 1){
sum += *w++;
nleft -= 2;
}
sum = (sum >> 16) + (sum & 0xFFFF);
sum += (sum >> 16);
answer = ~sum;
return(answer);
}
People, i've tried, i understand and know how to calculate using ones complement, hex conversion, binary conversion, AND, OR, XOR, NOT, and everything, but i can't do this .
Does anyone know the answer to this?
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Hello
I am communicating with two devices using my computer over UDP protocol. The application is running fine. When I monitored the UDP traffic using Wireshark software, I found that there were too many Checksum errors.
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Hi,
I have an input like this
1 2 3 4
2 3 4 5
4 5 6 7
I would like to count the no. of columns and print a header with a prefix "Col".
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number:department:amount
125:Market:125.23
126:Hardware store:434.95
127:Video store:7.45
128:Book store:14.32
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Discussion started by: verdepollo
3 Replies
LEARN ABOUT DEBIAN
sum
SUM(1) User Commands SUM(1)NAME
sum - checksum and count the blocks in a file
SYNOPSIS
sum [OPTION]... [FILE]...
DESCRIPTION
Print checksum and block counts for each FILE.
-r use BSD sum algorithm, use 1K blocks
-s, --sysv
use System V sum algorithm, use 512 bytes blocks
--help display this help and exit
--version
output version information and exit
With no FILE, or when FILE is -, read standard input.
AUTHOR
Written by Kayvan Aghaiepour and David MacKenzie.
REPORTING BUGS
Report sum bugs to bug-coreutils@gnu.org
GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
General help using GNU software: <http://www.gnu.org/gethelp/>
Report sum translation bugs to <http://translationproject.org/team/>
COPYRIGHT
Copyright (C) 2011 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.
SEE ALSO
The full documentation for sum is maintained as a Texinfo manual. If the info and sum programs are properly installed at your site, the
command
info coreutils 'sum invocation'
should give you access to the complete manual.
GNU coreutils 8.12.197-032bb September 2011 SUM(1)
08-24-2009
.