B.P. PODDAR INSTITUTE OF MANAGEMENT AND TECHNOLOGY
137, V.I.P. ROAD, PODDAR VIHAR, KOLKATA – 700052
DEPARTMENT OF INFORMATION TECHNOLOGY
Term paper On
GUESS THE NUMBER PUZZLE USING SOCKET PROGRAMMING
Subject : COMPUTER NETWORKING (PCC CS602)
Third Year, Semester VI
Academic Year 2020-21
SUBMITTED by :
Ujjwal Kumar Singh - 11500218003
CONTENTS
Socket Programming
Sockets
Stages for Server Client-Server
communication
Guess the number puzzle using socket
programming
Conclusion
SOCKET PROGRAMMING
A SHORT INTRODUCTION
Socket programming is a way of connecting
two nodes on a network to communicate with
each other. One socket(node) listens on a
particular port at an IP, while other socket
reaches out to the other to form a
connection. Server forms the listener socket
while client reaches out to the server
What are Sockets?
A socket is one endpoint of a two
way communication link between two programs
running on the network. The socket mechanism
provides a means of inter-process communication
(IPC) by establishing named contact points
between which the communication take place.
Like ‘Pipe’ is used to create pipes and sockets is
created using ‘socket’ system call. The socket
provides bidirectional FIFO Communication facility
over the network. A socket connecting to the
network is created at each end of the
communication. Each socket has a specific
address. This address is composed of an IP
address and a port number.
Socket are generally employed in client server
applications. The server creates a socket,
attaches it to a network port addresses then waits
for the client to contact it. The client creates a
socket and then attempts to connect to the server
socket. When the connection is established,
transfer of data takes place.
Types of Sockets :
There are two types of Sockets:
the datagram socket and the stream socket.
1. Datagram Socket :
This is a type of network which has
connection less point for sending and
receiving packets. It is similar to mailbox.
The letters (data) posted into the box are
collected and delivered (transmitted) to a
letterbox (receiving socket).
2. Stream Socket
In Computer operating system, a stream
socket is type of interprocess
communications socket or network socket
which provides a connection-oriented,
sequenced, and unique flow of data without
record boundaries with well defined
mechanisms for creating and destroying
connections and for detecting errors. It is
similar to phone. A connection is
established between the phones (two ends)
and a conversation (transfer of data) takes
place.
Network socket
A network socket is a software structure within
a network node of a computer network that serves
as an endpoint for sending and receiving data
across the network. The structure and properties
of a socket are defined by an application
programming interface (API) for the networking
architecture. Sockets are created only during the
lifetime of a process of an application running in
the node.
Because of the standardization of
the TCP/IP protocols in the development of
the Internet, the term network socket is most
commonly used in the context of the Internet
Protocol Suite, and is therefore often also referred
to as Internet socket. In this context, a socket is
externally identified to other hosts by its socket
address, which is the triad of transport protocol, IP
address, and port number.
The term socket is also used for the software
endpoint of node-internal inter-process
communication (IPC), which often uses the same
API as a network socket.
Use
The use of the term socket in software is
analogous to the function of an electrical female
connector, a device in hardware for
communication between nodes interconnected
with an electrical cable. Similarly, the term port is
used for external physical endpoints at a node or
device.
The application programming interface (API) for
the network protocol stack creates a handle for
each socket created by an application, commonly
referred to as a socket descriptor. In Unix-like
operating systems, this descriptor is a type of file
descriptor. It is stored by the application process
for use with every read and write operation on the
communication channel.
At the time of creation with the API, a network
socket is bound to the combination of a type of
network protocol to be used for transmissions, a
network address of the host, and a port number.
Ports are numbered resources that represent
another type of software structure of the node.
They are used as service types, and, once created
by a process, serve as an externally (from the
network) addressable location component, so that
other hosts may establish connections.
Network sockets may be dedicated for persistent
connections for communication between two
nodes, or they may participate
in connectionless and multicast communications.
In practice, due to the proliferation of the TCP/IP
protocols in use on the Internet, the term network
socket usually refers to use with the Internet
Protocol (IP). It is therefore often also
called Internet socket.
Socket addresses
An application can communicate with a
remote process by exchanging data with
TCP/IP by knowing the combination of
protocol type, IP address, and port number.
This combination is often known as a socket
address. It is the network-facing access
handle to the network socket. The remote
process establishes a network socket in its
own instance of the protocol stack, and uses
the networking API to connect to the
application, presenting its own socket address
for use by the application.
Implementation
A protocol stack, usually provided by the operating
system (rather than as a separate library, for
instance), is a set of services that allow processes
to communicate over a network using the
protocols that the stack implements. The operating
system forwards the payload of incoming IP
packets to the corresponding application by
extracting the socket address information from the
IP and transport protocol headers and stripping the
headers from the application data.
The application programming interface (API) that
programs use to communicate with the protocol
stack, using network sockets, is called a socket
API. Development of application programs that
utilize this API is called socket
programming or network programming. Internet
socket APIs are usually based on the Berkeley
sockets standard. In the Berkeley sockets
standard, sockets are a form of file descriptor, due
to the Unix philosophy that "everything is a file",
and the analogies between sockets and files. Both
have functions to read, write, open, and close. In
practice the differences strain the analogy, and
different interfaces (send and receive) are used on
a socket. In inter-process communication, each
end generally has its own socket.
In the standard Internet protocols TCP and UDP, a
socket address is the combination of an IP
address and a port number, much like one end of
a telephone connection is the combination of
a phone number and a particular extension.
Sockets need not have a source address, for
example, for only sending data, but if a
program binds a socket to a source address, the
socket can be used to receive data sent to that
address. Based on this address, Internet sockets
deliver incoming data packets to the appropriate
application process.
Socket often refers specifically to an internet
socket or TCP socket. An internet socket is
minimally characterized by the following:



local socket address, consisting of the local
IP address and (for TCP and UDP, but not
IP) a port number
protocol: A transport protocol, e.g., TCP,
UDP, raw IP. This means that (local or
remote) endpoints with TCP port 53 and
UDP port 53 are distinct sockets, while IP
does not have ports.
A socket that has been connected to
another socket .
CLIENT-SERVER
COMMUNICATION
CLIENT
Initiates the communication
Must know the address and the port of the server
Active socket
SERVER
Passively waits for and responds to clients
Passive socket
SOCKET CREATION
int sockfd = socket(domain, type, protocol) sockid:
socket descriptor, an integer (like a file-handle)
domain: integer, communication domain e.g., AF_INET
(IPv4 protocol) , AF_INET6 (IPv6 protocol) type:
communication type SOCK_STREAM: TCP(reliable,
connection oriented) SOCK_DGRAM: UDP(unreliable,
connectionless) protocol: Protocol value for Internet
Protocol(IP), which is 0. This is the same number which
appears on protocol field in the IP header of a
packet.(man protocols for more details)
BIND
int bind(int sockfd, const struct sockaddr *addr,
socklen_t addrlen); After creation of the socket, bind
function binds the socket to the address and port
number specified in addr(custom data structure). In
the example code, we bind the server to the localhost,
hence we use INADDR_ANY to specify the IP address
LISTEN
int listen(int sockfd, int backlog); It puts the server
socket in a passive mode, where it waits for the client
to approach the server to make a connection
ACCEPT
int new_socket= accept(int sockfd, struct sockaddr
*addr, socklen_t *addrlen); It extracts the first
connection request on the queue of pending
connections for the listening socket, sockfd, creates a
new connected socket, and returns a new file
descriptor referring to that socket. At this point,
connection is established between client and server,
and they are ready to transfer data.
CONCLUSION
Network programming makes use of socket for
interprocess communication between hosts where
sockets act as the endpoint of the interprocess
communication. Here sockets can also be termed as
network socket or Internet socket since
communication between computers is based on
Internet protocol AFTER COMPLETING THIS
PRESENTATION ON SOCKET PROGRAMMING .WE
CAME TO KNOW ABOUT SO MANY TERMS RELATED TO
THIS TOPIC .FIRSTLY, WE HAVE LEARNT ABOUT SOCKET
AND IT'S TYPE THEN WE HAVE LEARNT ABOUT SOCKET
PROCEDURES ..,etc
THANK YOU
!!!!!!!!!!