The telnet client is a simple commandline utility that is used to connect to socket servers and exchange text messages. Here is an example of how to use telnet to connect to google.com and fetch the homepage. $ telnet google.com 80 The above command will connect to google.com on port 80. $ telnet google.com 80… Read More »
Whois The whois information of a domain name provides various details like registrar, owner, registration date, expiry date etc. The whois information is provided by the corresponding whois servers of the registrars. The information is available for free and most whois servers run a whois service on port 43 which provides whois data associated with… Read More »
UDP sockets UDP or user datagram protocol is an alternative protocol to its more common counterpart TCP. UDP like TCP is a protocol for packet transfer from 1 host to another, but has some important differences. UDP is a connection-less and non-stream oriented protocol. It means a UDP server just catches incoming packets from any… 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 »
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 »
Socket function – recv() If you are writing a socket program in python that communicates with some remote machine or server to receive data, then you shall be using the recv() function to receive data on a socket. The recv() can receive only a specified number of bytes into a string buffer. If the incoming… Read More »
Tutorial on how to code simple network servers and clients using low level Socket api in python.
Packet Sniffer Sniffers are programs that can capture/sniff/detect network traffic packet by packet and analyse them for various reasons. Commonly used in the field of network security. Wireshark is a very common packet sniffer/protocol analyzer. Packet sniffers can be written in python too. In this article we are going to write a few very simple… Read More »