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

2. TELNET PURPOSE: 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

3. TELNET ARCHITECTURE Telnet Client TCP Telnet SERVER Application Port 23 NVT TCP Connection

4. 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:25525024 Means: Will terminal type 24

5. TELNET SESSION Command 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