1 CS4550 Computer Networks II APPLICATIONS TELNET Feit Chap 13 FTP Feit Chap 14 E-Mail Feit Chap 16.

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CS4550 Computer Networks II

APPLICATIONS

TELNET Feit Chap 13FTP Feit Chap 14E-Mail Feit Chap 16

TELNETPURPOSE: Provide alphanumeric terminal

communication between two computers

INSTALLATION: Typically available as part of network

SW in W95, NT, unix

NETWORK SERVICES:

connection TCP

well known port 23

run from command prompt

TELNET ARCHITECTURE

Telnet Client

TCP TCP

Telnet SERVER

Application

Port 23

NVT

TCP Connection

Network Virtual Terminal (NVT)

Data Format : 8’th bit 0 ASCII 0 -127

Control Data: 8’th bit 1 ASCII 128-255

OPTIONS NEGOTIATION: (DO,WILL), (DO,WONT), (WILL,DO), (WILL,DON’T)

Option Codes: see Feit Table 13.3

Internet Assigned Numbers Authority,www.iana.org

Format : IAC request byte option code

Example:255 250 24

Means: Will terminal type 24

TELNET SESSIONCommand Format:

telnet hostname [port#]

Connecting to other ports example:

telnet cs.nps.navy.mil 25

220 cs.nps.navy.mil ESMTP Sendmail 8.9.2/8.9.2; Tue, 1 Feb 2000 09:18:09 -0800 PST)

HELO wolf

250 cs.nps.navy.mil Hello wolf.cs.nps.navy.mil [131.120.8.161], pleased to meet you

quit

221 cs.nps.navy.mil closing connection

1 CS4550 Computer Networks II APPLICATIONS TELNET Feit Chap 13 FTP Feit Chap 14 E-Mail Feit Chap 16.

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