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Installing Telnet on a newer Mac

Videot27

Videot27

macrumors newbie
Original poster
Apr 2, 2010
20
6
Chicago
Hi, all —

I have an archaic piece of hardware on my network at work which still requires me to use Telnet to check its available disk space (long story). I always did that via Telnet, but since I got my cheese-grater Mac, I've been unable to do it as Telnet functionality isn't there any more.
I've followed the tutorials online and added Homebrew. The next step is supposed to be simply to issue this command:

brew install telnet

But I get this error when I do:

==> Fetching telnet
==> Downloading https://ghcr.io/v2/homebrew/core/telnet/manifests/64
curl: (35) error:02FFF036:system library:func(4095):Connection reset by peer
Error: telnet: Failed to download resource "telnet_bottle_manifest"
Download failed: https://ghcr.io/v2/homebrew/core/telnet/manifests/64

This page — https://formulae.brew.sh/formula/telnet — seems to indicate that it should work on Monterey (I'm on version 12.6), so does anyone have any idea what I'm doing wrong? I can't really buy a Telnet app for work, plus this seems like such basic Unix stuff that it shouldn't be impossible to implement for free.
I'd appreciate any useful input.

Thanks in advance.

— Mike
 
Doing that exact installation works perfectly fine for me on Monterey. I am, based on the log, going to say it was a temporary network fluke. Try again. If it still doesn't work I would check if there's a network blog for ghcr.io
 
casperes1996 said:
Doing that exact installation works perfectly fine for me on Monterey. I am, based on the log, going to say it was a temporary network fluke. Try again. If it still doesn't work I would check if there's a network blog for ghcr.io
Click to expand...
I've sent a message to our network guy... I'm wondering if any kind of Telnet activity is firewalled out for security reasons. It's just that in my case, I'd be telnetting into a piece of legacy hardware which itself is firewalled in by having an internal IP address that can't communicate on our outside IP range.

It's frustrating that Telnet functionality is just simple left out of the Mac OS anymore. Hello, Apple, some people really do still use that stuff!
 
Videot27 said:
I've sent a message to our network guy... I'm wondering if any kind of Telnet activity is firewalled out for security reasons. It's just that in my case, I'd be telnetting into a piece of legacy hardware which itself is firewalled in by having an internal IP address that can't communicate on our outside IP range.

It's frustrating that Telnet functionality is just simple left out of the Mac OS anymore. Hello, Apple, some people really do still use that stuff!
Click to expand...

No doubt it is firewalled off for security reasons. Every single packet sent over something that isn't SSL related is transmitted in clear text. Anyone with a packet analyzer can sniff those packets, examine them and if they contain them, extract usernames and passwords from them. That's a major security vulnerability that everyone has been getting away from since the early 2000s.

So telnet, rsh, ftp, tftp, rlogin.. all of those old BSD services that do not use SSL are vulnerabilities that have been firewalled off if not completely disabled and uninstalled from every network device if possible.

BL.
 
There are also Web based telnet apps like this one I found through a quick search:

Telnet Online

telnet, ping, traceroute, md5, sha1 online service. ÑелнеÑ(telnet), пинг(ping), ÑÑÑйÑÑоÑÑ(traceroute) ÑеÑвиÑ
telnet-online.net telnet-online.net

I'm not endorsing that one. I have no idea if that one's trustworthy, but there are plenty of others.
 
Been a while since I've had to telnet into something, but along the lines of nc, can't ssh get the job done?
 
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smirking said:
There are also Web based telnet apps like this one I found through a quick search:

Telnet Online

telnet, ping, traceroute, md5, sha1 online service. ÑелнеÑ(telnet), пинг(ping), ÑÑÑйÑÑоÑÑ(traceroute) ÑеÑвиÑ
telnet-online.net telnet-online.net

I'm not endorsing that one. I have no idea if that one's trustworthy, but there are plenty of others.
Click to expand...
A web client probably wouldn't work because the OP wants to telnet to something on the network, so it's not available on the internet.
 
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Videot27 said:
Hi, all —

I have an archaic piece of hardware on my network at work which still requires me to use Telnet to check its available disk space (long story). I always did that via Telnet, but since I got my cheese-grater Mac, I've been unable to do it as Telnet functionality isn't there any more.
I've followed the tutorials online and added Homebrew. The next step is supposed to be simply to issue this command:

brew install telnet

But I get this error when I do:

==> Fetching telnet
==> Downloading https://ghcr.io/v2/homebrew/core/telnet/manifests/64
curl: (35) error:02FFF036:system library:func(4095):Connection reset by peer
Error: telnet: Failed to download resource "telnet_bottle_manifest"
Download failed: https://ghcr.io/v2/homebrew/core/telnet/manifests/64

This page — https://formulae.brew.sh/formula/telnet — seems to indicate that it should work on Monterey (I'm on version 12.6), so does anyone have any idea what I'm doing wrong? I can't really buy a Telnet app for work, plus this seems like such basic Unix stuff that it shouldn't be impossible to implement for free.
I'd appreciate any useful input.

Thanks in advance.

— Mike
Click to expand...
I remember I used those apps in the Mac OS 8 days. In OSX does not the terminal also work? In did for me in Tiger (last times I used Telnet).
 
You might be able to build it from source:
github.com

src/usr.bin/telnet at master · openbsd/src

Read-only git conversion of OpenBSD's official CVS src repository. Pull requests not accepted - send diffs to the tech@ mailing list. - openbsd/src
github.com github.com

That's from OpenBSD though, so I'm not sure if it would work on Mac.
 
Videot27 said:
I've sent a message to our network guy... I'm wondering if any kind of Telnet activity is firewalled out for security reasons. It's just that in my case, I'd be telnetting into a piece of legacy hardware which itself is firewalled in by having an internal IP address that can't communicate on our outside IP range.

It's frustrating that Telnet functionality is just simple left out of the Mac OS anymore. Hello, Apple, some people really do still use that stuff!
Click to expand...
Did they remove it? It was with Tiger (last time I used Telent).
 
NoBoMac said:
Been a while since I've had to telnet into something, but along the lines of nc, can't ssh get the job done?
Click to expand...

To a degree, there are some things that telnet can do that ssh can't. Telnet can tell you if a given port on a server is open if you try to connect directly to that port. nc can do the same, but it's hard to get that same response out of ssh, because it depends on the SSL layer being there. For example, if I wanted to test relaying mail without going through a dedicated mail client, I could telnet to port 25 on a server, and send commands directly to the mail transport agent. SSL wouldn't allow that because of it trying to use the SSL layer to get to the service, and when it doesn't, fails and exits.

jwolf6589 said:
Did they remove it? It was with Tiger (last time I used Telent).
Click to expand...

Telnet hasn't been installed since at least Snow Leopard. I didn't have it on my MBA when I bought it, and it came with Lion.

BL.
 
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bradl said:
To a degree, there are some things that telnet can do that ssh can't. Telnet can tell you if a given port on a server is open if you try to connect directly to that port. nc can do the same, but it's hard to get that same response out of ssh, because it depends on the SSL layer being there. For example, if I wanted to test relaying mail without going through a dedicated mail client, I could telnet to port 25 on a server, and send commands directly to the mail transport agent. SSL wouldn't allow that because of it trying to use the SSL layer to get to the service, and when it doesn't, fails and exits.



Telnet hasn't been installed since at least Snow Leopard. I didn't have it on my MBA when I bought it, and it came with Lion.

BL.
Click to expand...
I used use Telnet daily in the Mac OS 7-9.x days.
 
jwolf6589 said:
In OSX does not the terminal also work? In did for me in Tiger (last times I used Telnet).
Click to expand...

Terminal is fully functional, but you would still need a telnet program to launch from your shell in Terminal since no such program is included in a default install.

NoBoMac said:
Been a while since I've had to telnet into something, but along the lines of nc, can't ssh get the job done?
Click to expand...

adrianlondon said:
I'd recommend ssh over telnet due to its security.

Assuming you're connecting to a Unix host, ssh will be enabled by default.
Click to expand...

Did you not read the first post?

The user wants to connect to a specific legacy device.
 
Last edited:
Hi, all —

NC seems to be working fine for this case, so I'm going to stick with that. As to some of the other suggestions (all of which are appreciated, by the way):

SSH didn't work:

Unable to negotiate with [my legacy device's internal IP address] port 22: no matching key exchange method found. Their offer: diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1

...and HTML-based, online Telnet simulators didn't work either, and I presume that's because their code was operating outside our firewall here at work, but the IP address needed to connect is an internal address that can't be touched from outside our firewall. The box in question serves video content, but has no ready, built-in way to track drive space... I had to ask tech support, back in 2013 or -14, how to check it and all they could come up with was Telnetting in and invoking the Units command.

NC let me connect to the box just like I always did with Telnet, and I was able to check the available disk space as needed. Silly, but that's literally the ONE and ONLY thing I needed to do. All other control of the box happens via its own internal HTML interface (why they didn't include disk space on the dashboard there, I can't say, and the box was EOL'd many years ago and has no support from the manufacturer). A testament to its build quality is that it's been in use for many years, 24/7/365. The drag is that it's so outdated, technologically-speaking.

Anyway, thank you again to all who replied. I sincerely appreciate it.

- Mike
 
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Videot27 said:
The drag is that it's so outdated, technologically-speaking.
Click to expand...
...and that it could die at any point in time without warning taking all the data stored on it to the grave, and there won't be any quick replacement on hand since it's out of support.
 
Sadly, I have to keep a Windows in Parallels instance so I can use PuTTY. Putty for the Mac stopped being updated years ago and doesn't work on any new macOS software for the last half decade.

That error is telling me you are being blocked from brew possibly, telnet definitely.

"Connection reset by peer" is essentially a rude hangup. It means you have either been blocked by the server or something between you and the server is tampering with the TCP connection.
 
Last edited:
Videot27 said:
SSH didn't work
Click to expand...
The SSH error is probably fixable, and then you could just run a simple command from your local machine which will automatically log in to the remote one and get the disk utilisation. However, that would take more time that it'd save so you're doing the right thing just using "nc" and continuing as before.

I tend to spend more time automating things (hello Applescript!) than I save by doing things manually, but I love the smug feeling when it works 😄
 
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