are there specific echo and non-echo telnet ports

Question

I have few doubts regarding telnet and echo which I haven't got so far lucky with google (also to say I have done my homework)

• Does the telnet specification says that there are specific echo port and specific non-echo port?
• If yes, Do ports 23 and 10001 differs on that specifically?
• If conditional yes, is it some version of telnet protocol specific. In other words were those added after some specific iteration of telnet and/or are their fully compliant telnet clients and partially compliant one (regrading echo)?
• also whats the difference if any between localecho and remote echo? I believe I am talking about echo from server side (remote echo?) but in any case which is what?

I am not sure if there is telnet / protocol specific child stackoverflow site? If yes, can somebody point me there?

Answer 1

The IANA Service Name and Transport Protocol Port Number Registry contains all port number registrations and for Telnet it cites RFC 854 as specification which defines

Port Assignment

  When used for remote user access to service hosts (i.e., remote
  terminal access) this protocol is assigned server port 23
  (27 octal).  That is L=23.

For the Echo Protocol the RFC number RFC 862 which similarily defines

TCP Based Echo Service

One echo service is defined as a connection based application on TCP.
A server listens for TCP connections on TCP port 7.  Once a
connection is established any data received is sent back.  This
continues until the calling user terminates the connection.

The port number 10001 is registered for "SCP Configuration".

Answer 2

When a true Telnet server starts, it sends a number of IAC commands to the client telling it how to behave. The server can tell the client to do its own character echo (IAC DO ECHO) or it can tell the client to act dumb (IAC DONT ECHO). The client then confirms its action (IAC WILL ECHO) or inaction (IAC WONT ECHO). If the client responds the opposite of what the server requests then the server can either adapt or continue to insist (and likely eventually fail).

https://www.rfc-editor.org/rfc/rfc857

So to answer your specific question, no, there are not different echo/noecho ports. It's a result of server configuration and client capability. Though technically it is possible to have the telnet server have different configuration on different ports.

You can find a list of special Telnet codes and available do/dont/will/wont options here:

http://www.laynetworks.com/telnet.htm