Quote of the Day (QOTD) Protocol

index.md

Quote of the Day

from https://www.gkbrk.com/wiki/qotd_protocol/

Tags: networking protocol

Quote of the Day is a simple protocol that is used to deliver daily quotes. Although its usage is almost nonexistent these days, there are still a few public servers. The protocol is defined by RFC 865. According to the RFC, a QOTD server is run on port 17 for TCP and UDP connections.

The RFC recommends that;

• The quotes should be limited to the ASCII printable characters, spaces and newlines.
• They should be less than 512 characters.

Since the protocol is only used to send quotes to terminals, these aren’t hard requirements. But a server should still follow these recommendations in order to be compatible with the other servers and clients.

Despite the name being Quote of the Day, a server does not have to serve daily quotes. It can change the quote at any interval or send random quotes at each connection.

TCP Connections

When a QOTD server gets a connection, it sends a quote and closes the connection, discarding any received data. Basically, a server should do the following

Listen to connections on port 17.

• Accept a connection.
• Choose a random quote.
• Send the quote to the client.
• Close the connection.

UDP Connections

A UDP server is a bit different from a TCP one. Since UDP has no concept of connections, a server just sends the quote after getting a UDP datagram.

Listen to UDP datagrams on port 17.

• When you get a UDP packet:
• Discard any data in the packet.
  • Send a UDP datagram containing the quote back to the client.
  • Public QOTD Servers

Server Address	TCP Port	UDP Port
djxmmx.net 17	17
cygnus-x.net	17	17

main.py

import socket
import random

quotes = [
    "Never do today what you can do tomorrow",
    "Nobody lies on the internet",
    "The cake is a lie"
]

server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.bind(("0.0.0.0", 17)) # Bind to port 17
server.listen(5)

while True:
    sock, addr = server.accept()
    quote = random.choice(quotes)    
    sock.send(f"{quote}\n".encode("utf-8"))
    sock.close()

Thank you @jamiekt.