Python supports socket programming by providing 'socket' module. Socket programming enables connections and communications between two nodes. One node runs a process that listens for the requests on a particular port while another node sends the requests. It's a server-client relationship between two nodes.
In the below example, we connect to any public website like www.bing.com over port 80 using ipv4 address family (socket.AF_INET) over TCP protocol (sokcet.SOCK_STREAM). For UDP protocol, you can use socket.SOCK_DGRAM.
import socket
import sys
hostname = "www.bing.com"
try:
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print ("Socket successfully created here")
except socket.error as err:
print ("Socket creation failed here with error %s" %(err))
# default port for socket
port = 80
try:
host_ip = socket.gethostbyname(hostname)
except socket.gaierror:
print ("Error resolving the host")
sys.exit()
# connecting to the server
s.connect((host_ip, port))
print (f"Socket successfully connected to {hostname}")
Writing a simple server-client program
We will create 2 programs - one will act as server while another will act as client.
server.py
#server side program
import socket
# create a socket object
s = socket.socket()
print ("Socket successfully created")
# choose any random available port
port = 4042
# Next bind to the port
# empty string makes listen from all computers in the network
s.bind(('', port))
print ("socket binded to %s" %(port))
# start listening
s.listen(5)
print ("socket started listening")
# a forever loop until we interrupt it or
# an error occurs
counter = 0
while counter < 5:
# Keep establishing connection with clients
c, addr = s.accept()
print ('Got a connection from', addr )
counter+= 1
# send a message to the client. encoding to send byte type.
c.send('We listened to you'.encode())
# Close the connection with the client
c.close()
# Breaking once connection closed
#break
client.py
# client side program
import socket
# Create a socket object
s = socket.socket()
# port where server side program is listening
port = 4042
# connect to the server on local computer
s.connect(('127.0.0.1', port))
# receive data from the server and decoding to get the string.
print (s.recv(1024).decode())
# close the connection
s.close()
Start the server process. python server.py
Start the client process. python client.py
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