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A list of fun destinations for telnet

telnet.org

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Re: A list of fun destinations for telnet

#81

Post by chasd00 »

tosti wrote: post #21
nomel wrote: post #12

Earlier quoted context omitted.

Wanting to know how email worked and then stumbling on it being mentioned next to the relevant RFCs was my first exposure! You could easily check pop3 mail over telnet, by sending all the commands by hand. HELO! I then made my first email client, then an RFC later, and after browsing the web through telnet for a while, made my first web server!

Telnet was among my debugging tools for web applications. And sending an email without line editing felt much more exciting than a dedicated mail client. Just dig the remote MX, telnet to port 25 and do it by hand. Marvelous!

I vaguely remember using telnet to debug nodes from behind load balancers. I would ssh to the load balancer ( just a freebsd box with Apache ). Then telnet from there to port 80 on one of the app servers and issue get requests (including headers) by hand to see what the loadbalancer was seeing in the responses. Very tedious, I can't remember why but i do remember a BOF literally standing behind me and forcing me to do this with telnet and not something like curl/wget.

Re: A list of fun destinations for telnet

#82

Post by efdee »

nomel wrote: post #12
augusteo wrote: post #4

The Star Wars ASCII animation was how I learned telnet existed. Felt like discovering a secret passage in the internet. There's something pure about text-based interfaces. No loading spinners, no JavaScript frameworks, no cookie banners. Just text.

Wanting to know how email worked and then stumbling on it being mentioned next to the relevant RFCs was my first exposure! You could easily check pop3 mail over telnet, by sending all the commands by hand. HELO! I then made my first email client, then an RFC later, and after browsing the web through telnet for a while, made my first web server!

I hate to be that guy, but HELO/EHLO is smtp, not pop3

Re: A list of fun destinations for telnet

#83

Post by chasd00 »

tgv wrote: post #23

~/work/...> telnet towel.blinkenlights.nl zsh: command not found: telnet

i bet this is something an ai could help with. "write a simple telnet client in python. It only needs to connect to the host and display what the host sends. conform to any connection initialization requirements per rfc 854". That would probably get you close.

/edit front page of google did this and it worked for me. Need to do a pip install telnetlib3

  import telnetlib3
  import sys

  def simple_telnet_client(host, port=23):
    """
    Connects to a telnet server and prints incoming data.
    Compliant with RFC 854 (via telnetlib handling of NVTs).
    """
    try:
        # Initialize connection
        print(f"Connecting to {host}:{port}...")
        tn = telnetlib3.Telnet(host, port)

        # Read and display output indefinitely until connection closes
        while True:
            # read_eager() reads data already available without blocking
            data = tn.read_eager()
            if data:
                sys.stdout.write(data.decode('ascii', errors='ignore'))
                sys.stdout.flush()

            # Check if socket is closed
            if tn.get_socket() is None:
                break

    except ConnectionRefusedError:
        print("Connection refused.")
    except Exception as e:
        print(f"An error occurred: {e}")
    finally:
        if 'tn' in locals():
            tn.close()
            print("\nConnection closed.")

  if __name__ == "__main__":
    # Example usage:
    # simple_telnet_client("telehack.com", 23)

    # Replace with desired host
    host = input("Enter host: ")
    simple_telnet_client(host)

Re: A list of fun destinations for telnet

#84

Post by ifh-hn »

kjs3 wrote: post #71
VMG wrote: post #28

Note that this is much more dangerous than visiting a website. ANSI escape sequences can seriously mess with your system, RCE included.

Note that this is much more dangerous than visiting a website. Are you being hyperbolic or do you seriously think the attack surface area of ANSI escape sequences is 'much more' than, say, Javascrpt?

JavaScript has to escape the browser sandbox, does telnet have a similar sandbox? Or can it access the system directly?

I don't know the answer but if telnet can directly access the system that seems more dangerous irrespective of the attack surface.

Re: A list of fun destinations for telnet

#85

Post by nomel »

efdee wrote: post #82
nomel wrote: post #12

Earlier quoted context omitted.

Wanting to know how email worked and then stumbling on it being mentioned next to the relevant RFCs was my first exposure! You could easily check pop3 mail over telnet, by sending all the commands by hand. HELO! I then made my first email client, then an RFC later, and after browsing the web through telnet for a while, made my first web server!

I hate to be that guy, but HELO/EHLO is smtp, not pop3

I stand corrected! In my defense, it's definitely been a long while. ;)

Re: A list of fun destinations for telnet

#86

Post by jagged-chisel »

nomel wrote: post #12
augusteo wrote: post #4

The Star Wars ASCII animation was how I learned telnet existed. Felt like discovering a secret passage in the internet. There's something pure about text-based interfaces. No loading spinners, no JavaScript frameworks, no cookie banners. Just text.

Wanting to know how email worked and then stumbling on it being mentioned next to the relevant RFCs was my first exposure! You could easily check pop3 mail over telnet, by sending all the commands by hand. HELO! I then made my first email client, then an RFC later, and after browsing the web through telnet for a while, made my first web server!

I fixed a client’s Outlook many years ago with telnet. The app just wouldn’t download email. No error.

So, with the guy looking over my shoulder, I telnet to the email server, list his messages, and discover that there’s an email with an attachment that’s too big for Outlook to handle. Read some basic info from the message so he could confirm that deleting the message was fine - deleted the message, and Outlook worked again.

Dude was thrilled. Fun times.

Re: A list of fun destinations for telnet

#89

Post by jfalcon »

Back in a time when you had to pay out the nose for long distance calling, you had outdial service through X.25 PSN or more often, as ARPANet turned into Internet, you had Telnet accessible outdials.

https://cdn.preterhuman.net/texts/underground/hacking/INTERN...

Too bad mobile killed the dialtone.

Re: A list of fun destinations for telnet

#90

Post by alexjplant »

augusteo wrote: post #4

The Star Wars ASCII animation was how I learned telnet existed. Felt like discovering a secret passage in the internet. There's something pure about text-based interfaces. No loading spinners, no JavaScript frameworks, no cookie banners. Just text.

I discovered Telnet from some schlocky book [1] my parents had bought at Barnes and Noble about "Ethical Hacking" written by a guy who was later given a "Security Charlatan of the Year" award at DEF CON 20. I'd no idea it was a protocol - I thought it was just a program that let you talk directly to services like SMTP. I found netcat and friends later and thus never really got to use telnet for its intended purpose.

[1] https://archive.org/details/unofficialguidet0000fadi_r0y3/pa...

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