Telnet commands and options

For information about Telnet connection negotiations, see RFC 2355. Table 1 describes the Telnet commands from RFC 854, when the codes and code sequences are preceded by an IAC. For more information about Telnet commands, see RFC 854.

Table 1. Telnet commands from RFC 854
Command	Code	Description
SE	X'F0'	End of subnegotiation parameters.
NOP	X'F1'	No operation.
Data Mark	X'F2'	The data stream portion of a Synch. This should always be accompanied by a TCP Urgent notification.
Break	X'F3'	NVT character BRK.
Interrupt Process	X'F4'	The function IP.
Abort output	X'F5'	The function AO.
Are You There	X'F6'	The function AYT.
Erase character	X'F7'	The function EC.
Erase Line	X'F8'	The function EL.
Go ahead	X'F9'	The GA signal.
SB	X'FA'	Indicates that what follows is subnegotiation of the indicated option.
WILL (option code)	X'FB'	Indicates the want to begin performing, or confirmation that you are now performing, the indicated option.
WON'T (option code)	X'FC'	Indicates the refusal to perform, or continue performing, the indicated option.
DO (option code)	X'FD'	Indicates the request that the other party perform, or confirmation that you are expecting the other party to perform, the indicated option.
DON'T (option code)	X'FE'	Indicates the demand that the other party stop performing, or confirmation that you are no longer expecting the other party to perform, the indicated option.
IAC	X'FF'	Data byte 255.

Table 2 lists the options available for Telnet commands from RFC 1060. For more information about Telnet protocols, see RFC 1060 and RFC 1011.

Table 2. Telnet command options from RFC 1060
Option	Option (Hex)	Name
0	0	Binary Transmission
1	1	Echo
2	2	Reconnection
3	3	Suppress Go Ahead
4	4	Approx Message Size Negotiation
5	5	Status
6	6	Timing Mark
7	7	Remote Controlled Trans and Echo
8	8	Output Line Width
9	9	Output Page Size
10	A	Output Carriage-Return Disposition
11	B	Output Horizontal Tab Stops
12	C	Output Horizontal Tab Disposition
13	D	Output Formfeed Disposition
14	E	Output Vertical Tabstops
15	F	Output Vertical Tab Disposition
16	10	Output Linefeed Disposition
17	11	Extended ASCII
18	12	Logout
19	13	Byte Macro
20	14	Data Entry Terminal
21	15	SUPDUP
22	16	SUPDUP Output
23	17	Send Location
24	18	Terminal Type
25	19	End of Record
26	1A	TACACS User Identification
27	1B	Output Marking
28	1C	Terminal Location Number
29	1D	Telnet 3270 Regime
30	1E	X.3 PAD
31	1F	Negotiate About Window Size
32	20	Terminal Speed
33	21	Remote Flow Control
34	22	Linemode
35	23	X Display Location
255	FF	Extended-Options-List