In a previous article on we saw how to construct raw icmp echo packets and send them out in large quantities to remote hosts in an attempt to bomb them. Now we are going to construct the same program for windows using the winsock socket api. The above code can be compiled using Microsoft Visual c++ 2010 express edition. Create a new project and add a c file and then copy paste the code and [...]

Communication over sockets involves 2 programs running on the same machine or on separate machines across a network. First is a socket server and the other is a socket client. Tcp stands for Transmission control protocol and it is the most common protocol being used for most of the network communication that takes place over internet or a lan. There are other important protocols like udp, arp, icmp and they are used mandatorily but in [...]

recv The recv function is used to receive data on a socket. For example here is the code to fetch the home page of www.msn.com The output might be something like this $ gcc simple_client.c && ./a.out Connected Data Send Reply received HTTP/1.1 200 OK Cache-Control: no-cache, no-store Pragma: no-cache Content-Type: text/html; charset=utf-8 Vary: Accept-Encoding P3P: CP="NON UNI COM NAV STA LOC CURa DEVa PSAa PSDa OUR IND" Set-Cookie: MC1=V=3&GUID=fd76ac7b61c9436f9a414441d186becd; domain=.msn.com; expires=Mon, 08-Sep-2014 09:58:09 GMT; [...]

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. In the TCP protocol first a connection is established by performing the 3 step handshake. This is done by calling the connect() socket function. However there is no such connection established in [...]

Socket programming with winsock This is a quick guide/tutorial to learning socket programming in C language on Windows. “Windows” because the code snippets shown over here will work only on Windows. The windows api to socket programming is called winsock. Sockets are the fundamental “things” behind any kind of network communications done by your computer. For example when you type www.google.com in your web browser, it opens a socket and connects to google.com to fetch [...]

Mac address or hardware address is a 48bit (6 character) wide address assigned to a network interface. It is important for the packet delivery between 2 devices like your computer and the router. Ethernet protocol uses the mac address to deliver it to the right network node. It looks like this 00-1E-58-B8-D4-69 ( the dash is not relevant). Mac address of any interface can also be changed ( called mac spoofing ) . Any network [...]

Tcp connect port scanning TCP connect() scanning is the most basic form of TCP scanning. The program performs a connect() command on those ports of the target machine which are to be checked. If the port is open then the connect() command will succeed and a connection will be established. If the port is closed the connect() function would simply timeout in the connection attempt. The simple steps would be : 1. Start a loop [...]

Raw sockets with winpcap A previous post explains how to send on windows xp. However the winsock api has limited raw socket support in windows versions greater than windows xp+sp1. Therefore winpcap has to be used to send raw packets on higher windows versions. Winpcap is a packet driver useful for packet capturing and sending raw packets on the windows platform. Raw means we have to cook the whole packet ourselves. A TCP packet for [...]

DNS Query Its no new fact that when we type a web address in our browser a dns request is immediately send by our browser to a DNS server to get the IP address of that web address.In winsock applications we achieve this by gethostbyname() and things are pretty simple.In this article we shall do this simple thing without the help of gethostbyname().We shall be sending DNS queries and receive the reply and extract the [...]

Introduction Ever since windows 2000/XP when IP_HDRINCL became a valid option for setsockopt() , WSAIoctl() had another option called SIO_RCVALL which enabled a raw socket to sniff all incoming traffic over the selected interface to whose IP the socket was bound.Hence to make a sniffer in Winsock he simple steps are : 1. Create a raw socket. 2. Bind the socket to the local IP over which the traffic is to be sniffed. 3. WSAIoctl() [...]