On Thu, 10 Mar 2022 11:41:15 +0000
Paul Howarth <p...@city-fan.org> wrote:

> On Thu, 10 Mar 2022 12:26:54 +0100
> Vitaly Zaitsev via devel <devel@lists.fedoraproject.org> wrote:
> 
> > On 10/03/2022 11:55, Alex wrote:
> > > May I suggest to leave at least the telnet protocol in curl-minimal
> > > for debugging purposes.  
> > 
> > Telnet is an extremely vulnerable protocol. It must be disable.
> > 
> > If you need it, you can always install libcurl-full.
> 
> I wonder, do you have the "telnet" program installed on your machine(s)?
> 
> I'd be surprised if anyone using curl's telnet *client* support wasn't
> aware that it was sending plain text over the network, possibly
> including any credentials that were being used. A telnet client is,
> however, a very useful debugging tool for various other network
> protocols, not just the telnet protocol itself. That is, I believe,
> what Alex was advocating for, since the curl tool's presence is
> well-nigh universal and hence always available for debugging some
> network issues.

Thanks Paul, that's exactly my point.
I agree that Telnet should not be offered as a service to the outside world,
but for debugging is it very helpfully.

Let me try to explain what the "telnet://" means for me.

```
With the telnet protocol in curl is a TCP Socket connection created and
therefore can be tested if a TCP connection to a remote destination can be
successful created.
```

Here a example test. I know that this could be also done with https but it's a
understandable example, IMHO.

```
echo -e 'GET / HTTP/1.1\r\nHost: www.google.com\r\n\r\n'|curl --ipv4 \
-vso /dev/null --ssl --tlsv1.3 telnet://www.google.com:443
*   Trying 172.217.19.132:443...
* TCP_NODELAY set
* Connected to www.google.com (172.217.19.132) port 443 (#0)
* Closing connection 0
```

> Paul.
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