Python - Networking

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Python Networking:

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-Sharing data between a Connected network(Wired/Wireless)

Python Network Services:

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There are two levels of network service access in Python. These are:

1. Low-Level Access(connect same system(client and server) via socket)

2. High-Level Access(Application level network protocols(HTTP, FTP.,,)

Socket:

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-A socket is the end-point in a flow of communication between two programs or communication channels operating over a network. 

Syntax:

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      g = socket.socket (socket_family, type_of_socket, protocol=value)

Some of the important server socket methods are:

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1) listen(): is used to establish and start TCP listener.

2) bind(): is used to bind address (host-name, port number) to the socket.

3) accept(): is used to TCP client connection until the connection arrives.

4) connect(): is used to initiate TCP server connection.

5) send(): is used to send TCP messages.

6) recv(): is used to receive TCP messages.

7) sendto(): is used to send UDP messages

8) close(): is used to close a socket.

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Step by step Socket programming

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Step1 : importing the socket library

        Ex:

            import socket

Step 2 : making a simple socket(Socket creation)

        Ex: 

            s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

        Here,

          1) AF_INET - address family ipv4(internet protocol version 4)

          2) SOCK_STREAM - Connection oriented TCP Protocol

Step 3: Connecting to a server (find the ip of the server)

        Ex:

             import socket 

             ip = socket.gethostbyname('www.google.com')

             print(ip)

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#Program 1: find the ip of the server using Python

import socket

try:

    ip1 = socket.gethostbyname('www.google.com')

    ip2 = socket.gethostbyname('www.gmail.com')

    ip3 = socket.gethostbyname('www.facebook.com')

    print(ip1)

    print(ip2)

    print(ip3)

except Exception as e1:

    print(e1)

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#Program 2: find the Machine host name using Python

import socket

try:

    ip1 = socket.gethostbyname(socket.gethostname())

    print(ip1)

except Exception as e1:

    print(e1)

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#Program 3 : An example script to connect to Google using socket programming in Python 

import socket # for socket 

import sys  

try: 

    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) 

    print ("Socket successfully created")

except Exception as err: 

    print ("socket creation failed with error : ",err) 

# default port for socket 

port = 80

try: 

    host_ip = socket.gethostbyname('www.google.com') 

except Exception as err1: 

    print ("there was an error resolving the host",err1)

    sys.exit() 

# connecting to the server 

s.connect((host_ip, port)) 

print ("the socket has successfully connected to google on port =",host_ip) 

Output:

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Socket successfully created

the socket has successfully connected to google on port == 216.58.200.132

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#Program 4 : Client and server Program

Step1: (save client1.py)

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# Import socket module 

import socket                

  

# Create a socket object 

s = socket.socket()          

  

# Define the port on which you want to connect 

port = 12345                

  

# connect to the server on local computer

ip1 = socket.gethostbyname(socket.gethostname())

s.connect((ip1, port)) 

  

# receive data from the server 

print(s.recv(1024)) 

# close the connection 

s.close()        

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Step2: (server1.py)

# first of all import the socket library 

import socket                

  

# next create a socket object 

s = socket.socket()          

print ("Socket successfully created")

  

# reserve a port on your computer in our 

# case it is 12345 but it can be anything 

port = 12345                

  

# Next bind to the port 

# we have not typed any ip in the ip field 

# instead we have inputted an empty string 

# this makes the server listen to requests  

# coming from other computers on the network 

s.bind(('', port))         

print ("socket binded to %s" %(port)) 

  

# put the socket into listening mode 

s.listen(5)      

print ("socket is listening")

  

# a forever loop until we interrupt it or  

# an error occurs 

while True: 

  

   # Establish connection with client. 

   c, addr = s.accept()      

   print ('Got connection from', addr) 

  

   # send a thank you message to the client.  

   c.send('Thank you for connecting') 

  

   # Close the connection with the client 

   c.close() 

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