I am trying to send control + ] command in python using telnetlib library.
Currently I am doing:
tn.write('^]')
and also
tn.write('\x1D')
which i got from http://donsnotes.com/tech/charsets/ascii.html
To type control-A I use tn.write('\x01') and it works so I am confused why tn.write('\x1D') is not working for control-].
Thanks for any help
ctrl-] cannot be sent on the wire. You have to use a, let's say, synonym for it like close()
For further reading, see the pinpoint answer here: https://mail.python.org/pipermail/python-list/2012-December/636929.html
The ^] command is not actually sent to the server. It is a command to the telnet client. When you run the telnet program (not related to python at all) you see:
~$ telnet localhost 2050
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
That means ^] is a escape character. It is a way to make the local telnet program exit the input mode that sends everything to the server, and enter the input mode that accepts local commands. When you type ^] in this case, the telnet program won't send it to the server, it will just change the input mode.
Since you're connecting using the telnet protocol directly to the server, and not using the telnet program, it doesn't make sense to send ^].
Related
I'm working on a code that uses telnetlib of python to connect to a router and execute commands and stores the output in a file.
I'm using read_until('#') function and expecting a Router prompt, then execute the next command but my code freezes when I receive a '--More--' data from the remote telnet side. I tried using a pattern match to find '--More--' but then sometime the --More-- keyword doesn't come at once.
Any suggestion ?
Do I have to send some IAC command to the remote telnet side ?
sometime the --More-- keyword doesn't come at once
Try passing in a timeout.
Example: set timeout to 5 seconds for read_until():
read_until('--More--', 5)
Alternatively, you could use the expect() function to look for either '#' or '--More--' with a timeout:
expect(['#', '--More--'], 5)
Is it possible to telnet to a server and from there telnet to another server in python?
Since there is a controller which I telnet into using a username and password, and from the controller command line I need to login as root to run linux command. How would I do that using python?
I use the telentlib to login into router controller but from the router controller I need to log in again to get into shell. Is this possible using python?
Thanks!
Just checked it with the hardware I have in hand & telnetlib. Saw no problem.
When you are connected to the first device just send all the necessary commands using telnet.write('cmd'). It may be sudo su\n, telnet 192.168.0.2\n or whatever else. Telnetlib keeps in mind only its own telnet connection, all secondary connections are handled by the corresponding controllers.
Have you looked into using expect (there should be a python binding); basically, what I think you want to do is:
From your python script, use telnetlib to connect to server A (pass in username/password).
Within this "socket", send the remaining commands, e.g. "telnet serverB" and use expect (or some other mechanism) to check that you get back the expected "User:" prompt; if so, send user and then password and then whatever commands, and otherwise handle errors.
This should be very much doable and is fairly common with older stuff that doesn't support a cleaner API.
You can use write() to issue the sudo command.
tn.write("sudo\n")
You could also use read_until() to help with the credentials.
tn.read_until("login: ")
tn.write(user + "\n")
if password:
tn.read_until("Password: ")
tn.write(password + "\n")
I am trying to telnet into a altusen power KVM and reboot a computer.
when doing this using the windows telnet it works great.
but when I use python's telnetlib, all read commands fail
(not immediately but on timeout)
again when using the windows telnet everything works fine, and I can see the login message
the following is the code I use: [on python 2.7.3]
import telnetlib
tn = telnetlib.Telnet("11.11.11.11")
print tn.read_all()//timeout fail,windows telnet does get a response
okay to clearify:
python No user input gets nothing read_all() times out
normal windows telnet client No user input gets the following:
** ALTUSEN -- PN9108 Configuring Through Telnet **
Login:
I am trying to send commands to a server via a python script. I can see the socket connection being established on the server. But the commands I am sending across , do not seem to make it through(server does a read on the socket).
The server currently supports a telnet command interpreter. ie: you telnet to the command address and port, and you can start sending
string commands.
My question is , is there anything fundamentally different from sending strings over a tcp socket, as opposed to using telnet.
I have used both raw sockets as well as the Twisted framework.
Telnet is a way of passing control information about the communication channel. It defines line-buffering, character echo, etc, and is done through a series of will/wont/do/dont messages when the connection starts (and, on rare occasions, during the session).
That's probably not what your server documentation means. Instead, it probably means that you can open a TCP socket to the port using a program like "Telnet" and interact with a command interpreter on the server.
When the Telnet program connects, it typically listens for these control messages before responding in kind and so will work with TCP/socket connections that don't actually use the telnet protocol, reverting to a simple raw pipe. The server must do all character echo, line buffering, etc.
So in your case, the server is likely using a raw TCP stream with no telnet escape sequences and thus there is no difference.
Keep in mind that Telnet is an application layer protocol while TCP is a transport layer protocol. Telnet uses TCP in order to transmit data. That is a big fundamental difference between Telnet and TCP.
See: OSI Model wikipedia page
From the Wikipedia page on telnet
...User data is interspersed in-band with Telnet control information...
So, to answer your question, yes, telnet does differ from a raw socket.
RFC 854 describes the telnet protocol if you want to try implementing it or you could use telnetlib if you'd prefer an existing python client.
I want to write a Python Twisted server that serves text to its clients, and I want the clients to be able to write text back to manipulate the server. I will use Telnet, and the clients will use Putty or some similar terminal...I would also be open to using SSH if it is easier to do this.
My question is, how do I configure the server so that the client can send raw, unbuffered bytes (I don't want the user to have to press enter after a command)? Also, is there a way to change the configuration mid-session so that I can change back and forth to and from buffered/unbuffered bytes?
I think it is Telnet option 34 "Linemode" --- http://www.freesoft.org/CIE/RFC/1700/10.htm
I just don't know how to set up Twisted to use that...
Any help setting this up for Telnet or SSH is appreciated!!!
Thanks!
twisted.conch.telnet.TelnetBootstrapProtocol is a good example of how to do some option negotiation. It also happens to perform some LINEMODE negotiation. Take a look at the implementation for details, but here's a snippet that shows the server asking the client to enable linemode, naws, and sga:
for opt in (LINEMODE, NAWS, SGA):
self.transport.do(opt).addErrback(log.err)
A real server might want to do more error handling than log.err if the negotiation fails, since the client will be left in a state that is presumably not ideal for use with the server.
Also take a look at some of the funky terminal demos that come with Twisted. These do lots of character-at-a-time processing.