A report on Telnet

A telnet client accessing the Busybox in a router.

Application protocol used on the Internet or local area network to provide a bidirectional interactive text-oriented communication facility using a virtual terminal connection.

- Telnet
A telnet client accessing the Busybox in a router.

24 related topics with Alpha

Overall

Example of tunneling an X11 application over SSH: the user 'josh' has "SSHed" from the local machine 'foofighter' to the remote machine 'tengwar' to run xeyes.

Secure Shell

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Cryptographic network protocol for operating network services securely over an unsecured network.

Cryptographic network protocol for operating network services securely over an unsecured network.

Example of tunneling an X11 application over SSH: the user 'josh' has "SSHed" from the local machine 'foofighter' to the remote machine 'tengwar' to run xeyes.
Logging into OpenWrt via SSH using PuTTY running on Windows.
Diagram of the SSH-2 binary packet.

SSH was designed on Unix-like operating systems, as a replacement for Telnet and for unsecured remote Unix shell protocols, such as the Berkeley Remote Shell (rsh) and the related rlogin and rexec protocols, which all use insecure, plaintext transmission of authentication tokens.

Application layer

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Abstraction layer that specifies the shared communications protocols and interface methods used by hosts in a communications network.

Abstraction layer that specifies the shared communications protocols and interface methods used by hosts in a communications network.

Remote login to hosts: Telnet

A Simplified TCP State Diagram. See TCP EFSM diagram for a more detailed state diagram including the states inside the ESTABLISHED state.

Transmission Control Protocol

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One of the main protocols of the Internet protocol suite.

One of the main protocols of the Internet protocol suite.

A Simplified TCP State Diagram. See TCP EFSM diagram for a more detailed state diagram including the states inside the ESTABLISHED state.
Connection termination
TCP sequence numbers and receive windows behave very much like a clock. The receive window shifts each time the receiver receives and acknowledges a new segment of data. Once it runs out of sequence numbers, the sequence number loops back to 0.

Some examples include: FTP (20 and 21), SSH (22), TELNET (23), SMTP (25), HTTP over SSL/TLS (443), and HTTP (80).

Illustration of starting a passive connection using port 21

File Transfer Protocol

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Standard communication protocol used for the transfer of computer files from a server to a client on a computer network.

Standard communication protocol used for the transfer of computer files from a server to a client on a computer network.

Illustration of starting a passive connection using port 21

Telnet (TYPE A T and TYPE E T) – the file contains Telnet (or in other words, ASCII C0) carriage control characters (CR, LF, etc)

A conceptual diagram of a local area network using bus network topology.

Local area network

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Computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building.

Computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building.

A conceptual diagram of a local area network using bus network topology.
Twisted pair LAN cable

The TCP/IP-based LAN successfully supported Telnet, FTP, and a Defense Department teleconferencing application.

The DEC VT100, a widely emulated computer terminal

Computer terminal

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Electronic or electromechanical hardware device that can be used for entering data into, and transcribing data from, a computer or a computing system.

Electronic or electromechanical hardware device that can be used for entering data into, and transcribing data from, a computer or a computing system.

The DEC VT100, a widely emulated computer terminal
IBM 2741, a widely emulated computer terminal in the 1960s and 1970s (keyboard/printer)
A Teletype Model 33 ASR teleprinter, usable as a terminal
Closeup of an IBM 2741 printing terminal, which used a changeable Selectric "golfball" typing element and was faster than the earlier teletype machines
IBM 2250 Model 4, including light pen and programmed function keyboard
A Televideo ASCII character mode terminal
A typical text terminal produces input and displays output and errors
Nano text editor running in the xterm terminal emulator

Today, most PC telnet clients provide emulation of the most common terminal, the DEC VT100, using the ANSI escape code standard X3.64, or could run as X terminals using software such as Cygwin/X under Microsoft Windows or X.Org Server software under Linux.

A screenshot of PuTTY running under Ubuntu MATE

PuTTY

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Free and open-source terminal emulator, serial console and network file transfer application.

Free and open-source terminal emulator, serial console and network file transfer application.

A screenshot of PuTTY running under Ubuntu MATE
A screenshot of PuTTY running under Ubuntu MATE

It supports several network protocols, including SCP, SSH, Telnet, rlogin, and raw socket connection.

Berkeley r-commands

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The Berkeley r-commands are a suite of computer programs designed to enable users of one Unix system to log in or issue commands to another Unix computer via TCP/IP computer network.

The Berkeley r-commands are a suite of computer programs designed to enable users of one Unix system to log in or issue commands to another Unix computer via TCP/IP computer network.

rlogin is similar to the Telnet command, but is not as customizable and is able to connect only to Unix-like hosts.

Bruce Sterling, author of The Hacker Crackdown

Security hacker

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Someone who explores methods for breaching defenses and exploiting weaknesses in a computer system or network.

Someone who explores methods for breaching defenses and exploiting weaknesses in a computer system or network.

Bruce Sterling, author of The Hacker Crackdown

Other exploits would be able to be used through File Transfer Protocol (FTP), Hypertext Transfer Protocol (HTTP), PHP, SSH, Telnet and some Web pages.

Avaya ERS 2550T-PWR, a 50-port Ethernet switch

Network switch

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Networking hardware that connects devices on a computer network by using packet switching to receive and forward data to the destination device.

Networking hardware that connects devices on a computer network by using packet switching to receive and forward data to the destination device.

Avaya ERS 2550T-PWR, a 50-port Ethernet switch
A modular network switch with three network modules (a total of 24 Ethernet and 14 Fast Ethernet ports) and one power supply.
A 5-port layer-2 switch without management functionality
A rack-mounted 24-port 3Com switch
A couple of managed D-Link Gigabit Ethernet rackmount switches, connected to the Ethernet ports on a few patch panels using Category 6 patch cables (all equipment is installed in a standard 19-inch rack)

Managed switches have one or more methods to modify the operation of the switch. Common management methods include: a command-line interface (CLI) accessed via serial console, telnet or Secure Shell, an embedded Simple Network Management Protocol (SNMP) agent allowing management from a remote console or management station, or a web interface for management from a web browser. Examples of configuration changes that one can do from a managed switch include: enabling features such as Spanning Tree Protocol or port mirroring, setting port bandwidth, creating or modifying VLANs (virtual LANs), etc. Two sub-classes of managed switches are smart and enterprise managed switches.