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Understanding TCP/IP by Libor Dostálek, Alena Kabelová

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12.2 Telnet Protocol Commands

The IAC (Interpret As Command) character’s decimal value is 255 (FF in the hexadecimal notation) and is of special significance. If a character of this value is to be transmitted, it must be doubled. The IAC character is interpreted as the beginning of a Telnet protocol command.

This means the IAC character may be followed by the commands listed in the following table:

Command

  

Significance

Decimal Notation

Hexadecimal Notation

Symbol

 

236

EC

EOF

End of file

237

ED

SUSP

Suspend process

238

EE

ABORT

Abort process

239

EF

EOR

End of record

240

F0

SE

Sub option end

241

F1

NOP

No operation

242

F2

DM

Data mark (usually mark urgent data in TCP segment)

243

F3

BRK

Break process

244

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