Telnet Server Library

import socket
import select

# Telnet Server
# By MegaLoler
# Version 0.1

# The TelnetClientConnection class
# This class handles the client connections
# Subclass this to define your own event handlers and then pass your subclass as the ConnectionClass argument in the TelnetServer class

class TelnetClientConnection:
    def __init__(self, sock, addr):
        self.sock = sock
        self.addr = addr

        self.buf = ""

        self.connected = True
        self.onConnect()

    def recv(self, data):
        try:
            data = data.decode()
            self.buf += data

            for char in data:
                self.onCharInput(char)

            if "\r\n" in self.buf:
                lines = self.buf.split("\r\n")
            elif "\r\x00" in self.buf:
                lines = self.buf.split("\r\x00")
            else:
                lines = None

            if lines:
                self.buf = lines.pop()
                for line in lines:
                    self.onLineInput(line.strip())
        except UnicodeDecodeError as exception:
            pass

    # Commands

    # Disconnects the client
    def disconnect(self):
        self.sock.close()

        self.connected = False
        self.onDisconnect()

    # Sends exact data
    def send(self, data):
        if self.connected: self.sock.send(data.encode())

    # Sends a line of data
    def sendLine(self, line):
        self.send(line.strip() + "\r\n")

    # Events

    # Triggered when the connection is established
    def onConnect(self):
        print("[TELNET] " + str(self.addr) + " has connected.")
        self.sendLine("Welcome to this telnet server thingy!")

    # Triggered when the connection is broken
    def onDisconnect(self):
        print("[TELNET] " + str(self.addr) + " has disconnected.")

    # Triggered when a single character is sent from the client (only works if the telnet client is in char mode)
    def onCharInput(self, char):
        pass

    # Triggered when the client presses enter
    def onLineInput(self, line):
        print("[TELNET] " + str(self.addr) + ": " + line)
        self.sendLine("I'd like to inform you that you typed \"" + line + "\"")

# The TelnetServer class
# Use the ConnectionClass parameter when you define your own subclasses of TelnetClientConnection to handle the events

class TelnetServer:
    def __init__(self, host = socket.gethostname(), port = 23, maxQueue = 5, ConnectionClass = TelnetClientConnection):
        self.sock = socket.socket()
        self.sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        self.sock.bind((host, port))
        self.sock.listen(maxQueue)

        self.ConnectionClass = ConnectionClass
        self.clients = {}

        self.running = False

    # Start the server
    def start(self):
        if not self.running:
            self.running = True

            while self.running:
                (rlist, wlist, xlist) = select.select(list(self.clients.keys()) + [self.sock], [], [])
                for s in rlist:
                    if s == self.sock:
                        (client, address) = self.sock.accept()
                        self.clients[client] = self.ConnectionClass(client, address)
                    else:
                        data = s.recv(1024)
                        if len(data) == 0:
                            self.clients[client].disconnect()
                            del self.clients[client]
                        else:
                            self.clients[client].recv(data)

    # Stop the server
    def stop(self):
        if self.running:
            self.running = False

if __name__ == "__main__":
    TelnetServer(port = 1234).start()