File Transfer Protocol: Serial FTP

Reverse telnet is a specialized application of telnet, where the server side of the connection reads and writes data to a TTY line (RS-232 serial port), rather than providing a command shell to the host device. Typically, reverse telnet is implemented on an embedded device (e.g. terminal/console server), which has an Ethernet network interface and serial port(s). Through the use of reverse telnet on such a device, IP-networked users can use telnet to access serially-connected devices.

In the past, reverse telnet was typically used to connect to modems or other external asynchronous devices. Today, reverse telnet is used mostly for connecting to the console port of a router, switch or other device.

Example

On the client, the command line for initiating a "reverse telnet" connection might look like this:

telnet 172.16.1.254 2002

(The syntax in the above example would be valid for the command-line telnet client packaged with many operating systems, including most Unices, or available as an option or add-on.)

In this example, 172.16.1.254 is the IP address of the server, and 2002 is the TCP port associated with a TTY line on the server.

A typical server configuration on a Cisco router would look like this:

version 12.3
service timestamps debug uptim
service timestamps log uptime
no service password-encryption
!
hostname Terminal_Server
!
ip host Router1 2101 8.8.8.8
ip host Router2 2102 8.8.8.8
ip host Router3 2113 8.8.8.8
!
!
interface Loopback0
description Used for Terminal Service
ip address 8.8.8.8 255.255.255.255
!
line con 0
exec-timeout 0 0
password MyPassword
login
line 97 128
transport input telnet
line vty 0 4
exec-timeout 0 0
password MyPassword
login
transport input none
!
end

Simple File Transfer Protocol, as defined by RFC 913, was proposed as an (unsecured) file transfer protocol with a level of complexity intermediate between TFTP and FTP.

It was never widely accepted on the Internet, and is now assigned Historic status by the IETF.

It is sometimes confused with SSH file transfer protocol, a secured file transfer protocol.

It runs through port 115, and often receives the acronym of SFTP. It has a command set of 11 commands and support three types of data transmission: ASCII, BINARY and CONTINUOUS. For systems which have "WORD SIZE" which are multiples of 8 bits, the implementation of BINARY and CONTINUOUS is the same.

The protocol supports the following:

1. User id based login (User-id/Password combination)
2. Hierarchical folders
3. File Management (Rename, Delete, Upload, Download, Download with overwrite, Download with append)

The protocol does not support random access inside a file (required for resuming interrupted transfers).

SFTP may refer to:

Relating to file transfer:

* SSH file transfer protocol, a network protocol designed by the IETF to provide secure file transfer and manipulation facilities over the secure shell (SSH) protocol. This is typically meant in context of file transfer.
* FTP over SSH, the practice of running an FTP session over SSH, sometimes called Secure FTP. Rarely used, because FTP's normal 2-channel nature makes such tunneling hard.
* Simple File Transfer Protocol, an unsecured and rarely-used file transfer protocol from the early days of the Internet.
* Serial File Transfer Protocol, a protocol used to transfer files between a PC and an embedded device using RS-232 or similar serial protocols.

SFTP may also refer to:

* Screened fully-shielded twisted pair, a kind of network cable, in contrast to FTP and STP
* Science for the People, a U.S. left-wing organization and magazine
* Six Flags Theme Parks, chain of amusement parks and theme parks.