Syn Flood Syn flood program sends out a large number of syn packets to a destination host such that the destination host gets under heavy pressure to reply to all of them and hence consumes huge amount of memory/cpu resources without any real purpose. This causes the services of the remote host to become unavailable… Read More »
Syn flood and raw sockets A syn flood program sends out large number of tcp syn packets to a remote host on a particular port number. Syn packets are intended to initiate a tcp connection. However if a large number of syn packets are send without any purpose, then then it would consume a lot… Read More »
One common adsense optimisation technique is to block low paying ads. The adsense interface allows users to block whole categories of ads like travel&tourism, real estate, health etc. Although the google adsense does try its best to serve the most relevant ads for a website based on its topic, keyword and content but sometimes when… Read More »
Text templates are often used to generate content like notification emails, invoices filled with the details of a customer or user. The best example would be a bulk email program that sends out emails to multiple users filling the details of the particular user in every individual mail. Text templates have place holders for fields… Read More »
Domdocument The domdocument class of Php is a very handy one that can be used for a number of tasks like parsing xml, html and creating xml. It is documented here. In this tutorial we are going to see how to use this class to parse html content. The need to parse html happens when… Read More »
Tcp/IP Socket programming Sockets enable your program or application to talk to other machines over the network. When you type in google.com in your browser, it talks to google.com over the internet and fetches the webpage. For socket programming we need to use the socket library or api which provides some very simple functions to… Read More »
Tcp connect port scanner in perl A tcp connect port scanner works on the principle of establishing a full tcp connection on a port it wants to check. Therefore a port scanner is quite easy to code, as it just connects to all required ports one by one and whenever a connection is established, reports… Read More »
Open ports When running any kind of server application like http or ftp server, or doing socket programming, it might so happen that a server program when recompiled/rerun fails to bind to a particular port number because that port number is already in use. In such a case, you can either restart the system or… Read More »
UDP – User Datagram Protocol sockets UDP is an alternative protocol to the more commonly used TCP protocol. It is a connection-less protocol where you directly send packets without have to establish a proper connection. UDP packets have smaller headers compared to TCP headers. Also data communication is faster since no acknowledgement is exchanged for… Read More »
Pcapy In the previous articles we coded packet sniffers in python using raw sockets. Now lets use the libpcap library for the same. Libpcap is the packet capture library for linux and has wrappers for most languages. In python there are multiple libpcap wrappers like pcapy, pypcap etc. In this article we shall use the… Read More »
Wrapper class for socket functions The standard socket library in C comes with a lot of functions for every task like connecting, sending data and receiving data etc. However knowing the syntax of all the functions and calling them again and again and in the right sequence could be a bit intimidating. Using a class… Read More »
Socket function – recv() If you are writing a network application using sockets in C that communicates with a remote server and fetches data, then you must be aware of the recv function that is used to receive data. The recv function can only receive a specified number of bytes in the response. If the… Read More »
UDP Sockets in Php In a previous article we learnt about writing simple server and clients using TCP sockets in php. In this article we are going to use udp sockets for the same. UDP sockets are much simpler to work with since they are connection-less. A udp server just has an socket that waits… Read More »
BSNL now a days is providing a adsl router made by SemIndia Systems and the model names are similar to DNA-A201 or DNA-A211-1. In this article we are going to hack into this router to learn more about it. You might not know that this small and innocent looking modem is actually a “Linux CPU”…. Read More »
UDP sockets UDP stands for User Datagram Protocol and is an alternative protocol to TCP the most common protocol used for data transfer over the internet. UDP is different from TCP in a number of ways. Most importantly UDP is a connectionless protocol. TCP vs UDP In the TCP protocol first a connection is established… Read More »
Nameservers are special servers running a DNS service to provide the ip address of a particular domain name. Different domains have different nameservers. Usually the nameservers are hosted and managed by the hosting server provider. If you are hosting your website on Bluehost for instance, the nameservers would be those of bluehost. Whereas if you… Read More »
Dropdown terminal is a very useful utility that shows a command line terminal in a dropdown popup on the screen just by pressing a button like F12. These provide easy access to the command line and enhance productivity on Linux Desktop. There are multiple packages available for Ubuntu and similar distros, that provide a dropdown… Read More »
UDP sockets This article describes how to write a simple echo server and client using udp sockets in C on Linux/Unix platform. UDP sockets or Datagram sockets are different from the TCP sockets in a number of ways. The most important difference is that UDP sockets are not connection oriented. More technically speaking, a UDP… Read More »
Port Forwarding Port forwarding is a configuration in the router of a LAN such that any connections to a specific port number on the public/wan ip of the router may be forwarded to a specific machine/ip inside the LAN. Most routers have configuration options to enable port forwarding. Testing Port Forwarding After setting up port… Read More »
Netcat is a commandline utility like telnet but with much more features. Learn to use netcat with these simple commands examples.