If you are monitoring services, you also might want to get informed about critical states via sms. Almost everyone has an old mobile phone at home. Why not using one of those old mobile-phones? In this article I will describe how to transform your raspberry into a mail2sms-gateway. This gateway will be able to:

• receive emails and forward them via sms
• receive sms and forward them via email
• provide a webinterface for sending sms manually

Around 10 years ago I played with network-sockets in C. Now I just want to refresh my knowledge a bit and write a very simple webserver. This webserver just displays a simple site. the side is hardcoded, but close enough to see how it works…

If you want to block Facebook in your network, you can use a proxy or simply block all the Ip-Ranges of Facebook. Whois can help us to find the Ip-Ranges.

http://www.bogotobogo.com/Embedded/Little_endian_big_endian_htons_htonl.php

https://computing.llnl.gov/tutorials/pthreads/#Abstract

Sometimes we have to calculate networks. We are interested in stuff like: networkid, subnetmask, min. hostip, max. hostip, how many hosts can we address in this network aso.. There are many tools for calculating networks. And they are perfectly good. If you need it in a c programm, there are libraries for that too. But I think it’s not neccessary to use libraries for that. If you calculate it manually, it’s just a matter of working with bits in a 32bit address, so it might be an quite easy task…

On this page is a list of howto-disable-sslv3-support on different Servers.

Here is a very nice article about hardening encryption for ssh-connections

DNS-Blacklist AHBLrecently stopped their services. Since that I had many problems with our spamfilters. They are still using this blacklist and give all the mails a higher score because AHBL doesn’t exist anymore.

The following entry in /etc/spamassassin/local.cf solvesthe problem(quick fix) :

score DNS_FROM_AHBL_RHSBL 0

Sometimes it is useful to compare to directories and display the differences. diff can do the trick for you

diff -r dir1/ dir2/

If you just want a overview about the differences then just use “brief”:

diff --brief -r dir1/ dir2/

git can show you the differences too, and it can do it colorful if you want

git diff dir1/ dir2/