PYTHON- NETWORK PROGRAMMING

 

What is sockets ?

                   Sockets are the endpoints  of a  bidirectional communications channel . Sockets may communicate within a process , between processes on the same machine, or between processes on different continents.

http   -  Not secure

https  -  Secure

S.no	Term & description
1	DOMAIN         The family of protocols that is used as the transport mechanism. these values are constants such as A S_INET_, PF_INET, PF_X25, and so on.
2	TYPE        The type of communications between the two  endpoints, typically SOCK_STREAM for connection-oriented protocols and SOCK_DGRAM  for connectionless protocols.
3	PROTOCOL          Typically zero, this may be used to identify a variant of a protocol within a domain and type .
4	HOSTNAME            The identifier of a network interface ? ·      A string, which can be a host name, a dotted-quad address, or an IPV6 address in colon(and possibly dot)notation
	·      A  string  "<broadcast>", which specifies an INADDR_BROADCAST address ·      A  zero-length string,, which specifies INADDR_ANY,or ·      An  integer, interpreted as a binary address in host byte order
5	PORT        Each server listens for clients calling on one more ports. a port may be a fixnum port number, a string containing a port number, or the name of a service

 

SERVER SOCKET METHODS

 

S.no	Method & description
1	s.bind() this method binds address(hostname, port number pair ) to socket
2	s.listen() this method sets up an start TCP listener
3	s.accept()  This passively accept TCP client connection, waiting until connection arrives(blocking)

 

CLIENT SOCKETS  METHODS

S.no	Method & description
1	s.connect() this method actively initiates TCP server connection.

 

Generel socket Methods

 

S.No	Method & Description
1	s.recv() This method recives  TCP messege
2	s.send() This method transmits TCP messege
3	s.recvfrom() This method recives UDP message
4	s.sendto() This method transmits UDP messege
5	s.close () This method closes socket
6	Socket.gethostname () Return  the  hostname

 

A Simple Server

 

# This  is server.py file

import socket

s=socket.socket()

host=socket.gethostname()

port=12345

s.bind((host,port))

s.listen(5)

while True:

  c,addr=s.accept()

  print('Got connection from',addr)

  c.send('Thank you for connecting')

  c.close()

A Simple Client

# This  is client.py file

import socket

s = socket.socket()

host = socket.gethostname()

port = 12345

s.connect((host,port))

print(s.recv(1024))

s.close

#following would start a server in backgroud .

$ python server.py &

 

# once server is started run client as follows:

$ python client.py

Output

got connection from ('127.0.0.1',48437)

thank you for connecting