TCP/IP Tutorial and Technical Overview - IBM Redbooks

► The NVT provides a local echo function.
All of these can be negotiated by the two hosts. For example, a local echo is
preferred because of the lower network load and superior performance, but there
is an option for using a remote echo (see Figure 13-3), although no host is
required to use it.
Keyboard
Figure 13-3 Telnet: Echo option
An NVT printer has an unspecified carriage width and page length. It can handle
printable ASCII characters (ASCII code 32 to 126) and understands some ASCII
control characters, such as those shown in Table 13-1.
Table 13-1 ASCII control characters
Command ASCII Action
NULL (NUL) 0 No operation.
Line feed (LF) 10 Moves printer to next line, keeping the
same horizontal position.
Carriage return (CR) 13 Moves the printer to the next left margin.
BELL (BEL) 7 Produces and audible or visible signal.
Backspace (BS) 8 Moves print head one character position
towards the left margin.
486 TCP/IP Tutorial and Technical Overview
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