In the message dated: Thu, 14 May 2009 14:35:46 +0200,
The pithy ruminations from Ralph Angenendt on
<Re: Where is telnet?> were:
=>
=> James Knott wrote:
=> > Any reason why you're using telnet instead of ssh? Ssh has many
=> > advantages over telnet.
Yes, ssh has many advantages over telnet if the aim is to establish a remote
login session. However, ssh is not an acceptable substitute for telnet if the
aim is to establish an unencrypted TCP/IP connection to an arbitry port in
order to exchange ASCII data. This is a common use of telnet as a network
troubleshooting tool.
=>
=> ssh -p 25 mail-server.example.com
=> ssh -p 110 mail-server.example.com
=> ssh -p 80 www.example.com
=>
Did you actually try those examples? They will fail when the
ssh_exchange_identification part of the client-side protocol negotiation times
out.
=> Need more reasons?
In the examples you gave, after the ssh client establishes a connection up
through OSI layer 4 (TCP) to the destination port, it then tries to negotiate
the layer 7 (presentation) protocols. These include ssh_exchange_identification
of the remote host, ssh key exchange, etc.
In the examples given above, the common daemons listening on those ports (SMTP,
POP3, HTTP) will not be able to complete the protocol negotiation with the ssh
client, so the session will fail. I am not aware of any ssh options to disable
all identification and encryption mechanisms so that ssh can function like
telnet.
This means that ssh cannot be used to, for example, connect to an SMTP server
on port 25 an issue the commands:
mail from: <[email protected]>
rcpt to: <[email protected]>
data
this is a mail message
.
I'd suggest using "socat" (a "netcat" work-alike) if telnet is not available.
Mark
=>
=> Ralph
_______________________________________________
maemo-users mailing list
[email protected]
https://lists.maemo.org/mailman/listinfo/maemo-users
