Python multiple telnet sessions

Question

I need to build a script to get the telnet output of as many hosts as possible and save them to a separate file for each host. The script should run as a daemon.

For the moment i have a function that encapsulates the logic for do it for a single host with telnetlib, but i do not how to proceed. I planned to open a process (multiprocessing.Process) for each host but i suspect it's going to be a resource waste and it must to exist a better way :)

def TelnetLogSaver(hostname,ip,filename):   
    # open files and telnet sessions
    f = open(filename,"a")
    tn = telnetlib.Telnet(ip,23,TIMEOUT)

    # login
    e = tn.read_until("Login: ")
    tn.write(USER+"\n")
    # and password
    e = tn.read_until("Password: ")
    tn.write(PASSWORD+"\n")

    # Connected. Start infinite loop to save messages log
    while True:
        e = tn.read_until(PROMPT,TIMEOUT)
        if e is not "":
            f.write(datetime.datetime.now().strftime("%Y-%m-%dT%H:%M:%S"))
            f.write(e)
            f.flush()

        # avoid session timeout
        tn.write("\n")
        e = tn.read_until(PROMPT

Answer 1

I believe the following should do what your require, I took your original code and made it into a type of thread:

import threading
import telnetlib
import datetime
import sys
# Global Variable Declarations
TIMEOUT = 30
USER = "Noel"
PROMPT = "Noel"


class listener(threading.Thread):
    def __init__(self, filename, ip):
        # Have to make a call to the super classes' __init__ method
        super(listener, self).__init__()
        self.f = open(filename,"a")
        try:
            self.tn = telnetlib.Telnet(ip, 23, TIMEOUT)
        except:
            print "Bad Connection"
            sys.exit(0)

    def run(self):
        # login
        e = self.tn.read_until("Login: ")
        self.tn.write(USER+"\n")
        # and password
        e = self.tn.read_until("Password: ")
        self.tn.write(PASSWORD+"\n")
        while True:
            e = self.tn.read_until(PROMPT, TIMEOUT)
            if e is not "":
                self.f.write(datetime.datetime.now().strftime("%Y-%m-%dT%H:%M:%S"))
                self.f.write(e.strip())
                self.f.flush()

            # avoid session timeout
            self.tn.write("\n")


if __name__ == "__main__":
    # Things to listen to is a dictionary of hosts and files to output
    # to, to add more things to listen to just add an extra entry into
    # the things_to_listen_to in the format: host : outputfile
    things_to_listen_to = {"localhost" :"localhost_output.txt"}
    # Thread holder is going to hold all the threads we are going to start
    thread_holder = []
    for host, file in things_to_listen_to.iteritems():
        thread_holder.append(listener(file, host))
    for thread in thread_holder:
        thread.run()

Hope this helps, if you have any problem update your question or leave a comment.