listen() function of socket class in Python

Overview:

Calling listen() makes a socket ready for accepting connections.
The listen() method should be called before calling the accept() method on the server socket.
The listen() function accepts a queue size through the parameter backlog. This denotes maximum number of connections that can be queued for this socket by the operating system. Once 'backlog' number of connections is in the socket's queue, the kernel will reject incoming connections to the socket.

Example – Quote of the day Server:

# ----- A Python program implementing a Quote of the Day server -----

import socket

import datetime

from random import randint

quotes = [ ("I love going to coffee shops and just sitting and listening.", "Julie Roberts"),

("Know thyself", "Socrates"),

("For knowledge itself is Power", "Francis Bacon"),

("Nothing is worth more than this day", "Goethe"),

("Ah! happy years! once more who would not be a boy","Byron: Child Harold")];

qotdPortNumber = 32017;

qotdServerSocket = socket.socket();

qotdServerSocket.bind(("127.0.0.1", qotdPortNumber));

qotdServerSocket.listen();

print("Quote of the day requests welcome:");

while(True):

(socketForClient, clientIP) = qotdServerSocket.accept();

# Pick a random quote

quoteIndex = randint(0, 4);

quoteOfTheDay = "%s - %s"%(quotes[quoteIndex][0],quotes[quoteIndex][1]);

encodedMsg = quoteOfTheDay.encode();

socketForClient.send(encodedMsg);

timeVal = datetime.datetime.now();

print("%s Just served: %s, to client with IP address and port: %s"%(timeVal, quoteOfTheDay, clientIP));

socketForClient.close();

Output:

Quote of the day requests welcome:

2019-06-26 15:30:10.179610 Just served: Ah! happy years! once more who would not be a boy - Byron: Child Harold, to client with IP address and port: ('127.0.0.1', 51243)

2019-06-26 15:30:23.094655 Just served: I love going to coffee shops and just sitting and listening - Julie Roberts, to client with IP address and port: ('127.0.0.1', 51244)

Example – Quote of the day Client:

# ----- Example Python program to connect to a Quote of the Day server -----

import socket

# Server IP address and Port

qotdServerIP = "127.0.0.1";

qotdServerPort = 32017;

# Create client socket instance

qotdClient = socket.socket();

# Connect to the quote of the day server

# No need to send any message to server

# Server replies with a quote upon receiving a client connection

qotdClient.connect((qotdServerIP, qotdServerPort));

# Get the reply

quoteOfTheDay = qotdClient.recv(1024);

# Print the reply

print("Quote of the day:%s"%quoteOfTheDay.decode());

Output:

Quote of the day:I love going to coffee shops and just sitting and listening. - Julie Roberts

Listen() function of socket class in Python

Overview:

Example – Quote of the day Server:

Output:

Example – Quote of the day Client:

Output: