.\" SCCSID: @(#)telnet.1c	8.1	9/11/90.TH telnet 1c.SH Nametelnet \- user interface to the TELNET protocol.SH Syntax\fBtelnet\fR [\|\fIhost\|\fR[\fIport\fR\|]\|].SH Description.NXR "telnet user interface".NXS "TELNET protocol" "telnet user interface"The.PN telnetinterfaceis used to communicate with another host using the TELNET protocol.  If .PN telnetis invoked without arguments, it enters command mode,which is indicated by the prompt, telnet>.In this mode,.PN telnetaccepts and executes the commands listed below.If it is invoked with arguments, it performs an.B opencommand (see below) with those arguments..PPOnce a connection is opened,.PN telnetenters input mode.The input mode is either character-at-a-time or line-by-line, depending on what the remote system supports.In character-at-a-time mode, text is sent to the remote host asit is typed.In line-by-line mode, text is echoed locally andonly completedlines are sent to the remote host.  The local-echo-character,initially ^E.turns the local echo on and off, which isuseful when you want to enter passwords without themechoing to the screen..PPIn either mode, if the.I localcharstoggle is TRUE (the default in line mode), then the user's .I quit,.I intr,and.I flush characters are trapped locally and sent as TELNETprotocol sequences to the remote side.  Options such as toggle.I autoflushand toggle.I autosynchflush previous terminal input, as in.I quitand.I intr, in addition to flushing subsequent output to the terminal untilthe remote host acknowledges the TELNET sequence..PPTo issue.PN telnetcommands when in input mode, precede them with the.PN telnetescape character, initially the control character followedby a right bracket (\fB^]\fR).When in command mode, use the normal terminal editing conventions..PPThe following commands are available:.NXR "telnet user interface" "command list".TP 15\fBopen\fP \fIhost\fP [ \fIport\fP ].NXR "open command (TELNET)"Opens a connection to the named host.  If no port numberis specified, .PN telnetattempts to contact a TELNET server at the default port.The host specification may be either a host nameor an Internet address specified in the dot notation.For further information, see .MS hosts 5 and.MS inet 3n ..TP.B close.NXR "close command (TELNET)"Closes a TELNET session and returns to command mode..TP.B quit.NXR "quit command (TELNET)"Closes any open TELNET session and exits.PN telnet ..TP.B z.NXR "z command (TELNET)"Suspends.PN telnet .This command only works when the user is using the .MS csh 1 ..TP\fBmode \fItype\fR.NXR "mode command (TELNET)"The.I typeis either.I line,for line-by-line mode, or.I character,for character-at-a-time mode.The local host asks the remote host for permission to go intoone or the other mode.  The remote host enters the requested mode if it is capable of it..TP.B status.NXR "status command (TELNET)"Shows the current status of .PN telnet .This includes the peer one is connected to, as wellas the state of debugging..TP.B display \fR[\fP \fIargument...\fP \fR]\fP.NXR "display command (TELNET)".brDisplays all, or some, of the.B setand.B togglevalues (see below)..TP.B ? \fR[\fP \fIcommand\fP \fR]\fP.NXR "? command (TELNET)".brAccesses on-line help.  With no arguments,.PN telnetprints a help summary.If a command is specified, .PN telnetprints the help information for that command..TP.B send \fIargument(s)\fP.NXR "send command (TELNET)".brSends one or more special character sequences to the remote host.One or more of the following arguments can be specified:.RS.TP.I escape.brSends the current.PN telnetescape character (initially the control character followed by aright bracket, \fB^]\fR)..TP.I synch.brSends the TELNET SYNCHsequence.This sequence causes the remote system to discard input thatwas previously entered but that it has not yet read.This sequence is sent as TCP urgentdata and may not work if the remote system is a 4.2 BSD system.  Ifit does not work, a lower case r may be echoed on the terminal screen..TP.I brk.brSends the TELNET BRK(Break) sequence, which may have significance to the remotesystem..TP.I ip.brSends the TELNET IP(Interrupt Process) sequence, which causes the remotesystem to abort the currently running process..TP.I ao.brSends the TELNET AO(Abort Output) sequence, which causes the remote system to flushall output.B fromthe remote system.B tothe user's terminal..TP.I ayt.brSends the TELNET AYT(Are You There)sequence.  The remote system may or may not respond..TP.I ec.brSends the TELNET EC(Erase Character)sequence, which causes the remote system to erase the last characterentered..TP.I el.brSends the TELNET EL(Erase Line)sequence, which causes the remote system to erase the line currentlybeing entered..TP.I ga.brSends the TELNET GA(Go Ahead)sequence.  Often this sequence has no significance to the remote system..TP.I nop.brSends the TELNET NOP(No OPeration)sequence..TP.I ?.brPrints out help information for the.B sendcommand..RE.TP.B set \fIargument value\fP.NXR "set command (TELNET)".brSets a.PN telnetvariable to a specific value.The off value turns off the function associated withthe variable.The current values of variables can be displayed with the.B displaycommand..PPThe following variables that can be specified:.RS.TP.I echo.brToggles between local echoingof entered characters, and suppressingechoing of entered characters when inline-by-line mode.  The value  is initially ^E..TP.I escape.brEnters the.PN telnetcommand mode when you are connected toa remote system.  The value is initiallythe control character followed by a left bracket(\fB^[\fR)..TP.I interrupt.brSends a TELNET IPsequence (see.B send.I ipabove)to the remote host if.PN telnetis in.I localcharsmode (see.B toggle.I localcharsbelow) and the.I interruptcharacter is typed.The initial value for the interrupt character isthe terminal's.B intrcharacter..TP.I quit.brSends a TELNET BRKsequence (see.B send.I brkabove)to the remote host if.PN telnetis in.I localcharsmode (see.B toggle.I localcharsbelow)and the.I quitcharacter is typed.The initial value for the quit character isthe terminal's.B quitcharacter..TP.I flushoutput.brSends a TELNET AOsequence (see.B send.I aoabove)to the remote host if.I telnetis in.I localcharsmode (see.B toggle.I localcharsbelow)and the.I flushoutputcharacter is typed.The initial value for the flush character is the terminal's.B flushcharacter..TP.I erase.brSends a TELNET ECsequence (see.B send.I ecabove)to the remote system if.I telnetis in.I localcharsmode (see.B toggle.I localcharsbelow),.B andif.I telnetis operating in character-at-time mode.The initial value for the erase character isthe terminal's.B erasecharacter..TP.I kill.brSends a TELNET ELsequence (see.B send.I elabove)to the remote system if.PN telnetis in.I localcharsmode (see.B toggle.I localcharsbelow).B andif.PN telnetis operating in character-at-a-time mode.The initial value for the kill character is the terminal's.B killcharacter..TP.I eof.brSends this character to the remote system if.PN telnetis operating in line-by-line mode and this character isentered as the first character on a line.The initial value of the eof character is the terminal's.B eofcharacter..RE.TP.B toggle \fIarguments...\fP.NXR "toggle command (TELNET)".brToggles (betweenTRUEandFALSE)flags that control how.PN telnetresponds to events.More than one argument may be specified andthe current value of these flags can be displayed with the.B displaycommand.Valid arguments for the .PN togglecommand are the following:.RS.TP.I localchars.brCauses the .IR flush ,.IR interrupt ,.IR quit ,.IR erase ,and.I killcharacters to be recognizedlocally and transformed into appropriateTELNET control sequences if this flag is set toTRUE.  (See.B setabove).  The appropriate TELNET control sequences are:.IR ao ,.IR ip ,.IR brk ,.IR ec ,and.IR el ,respectively.For more information see the.PN sendcommand.The initial value for this toggle is TRUE in line-by-line mode,and FALSE in character-at-a-time mode..TP.I autoflush.brCauses the .PN telnetcommand to not display any data on the user's terminaluntil the remote system acknowledges (via a TELNET.I Timing Markoption)that it recognized and processed the following TELNET sequences:.IR ao ,.IR intr ,or.I quit.Both .I autoflushand.I localcharsmust be TRUE for.I autoflushto work in this manner.The initial value for this toggle is TRUE if the terminal user did notspecify.PN "stty noflsh" .  Otherwise it is FALSE.  For further information, see.MS stty 1 ..TP.I autosynchCauses the TELNET SYNCHsequence to follow the TELNET sequence that is initiatedwhen either the.I intror.I quitcharacter is typed.The.I autosynchflag works in this manner when both the.I autosynchand.I localcharsare TRUE.This procedure shouldcause the remote system to begin throwing away all previouslytyped input until both of the TELNETsequences have been read and acted upon.The initial value of this toggle is FALSE..TP.I crmod.brToggles carriage return mode.When this mode is enabled, most carriage return characters received fromthe remote host are mapped into a carriage return followed bya line feed.It is useful onlywhen the remote host sends carriage returns but never line feeds.The initial value for this toggle is FALSE..TP.I debug.brToggles socket level debugging which is useful only to the.IR superuser.The initial value for this toggle is FALSE..TP.I options.brToggles the display of internal.PN telnetprotocol processing that deals with TELNEToptions.The initial value for this toggle is FALSE..TP.I netdata.brToggles the display of all network data (in hexadecimal format).The initial value for this toggle is FALSE..TP.I ?.brDisplays the legal.B togglecommands..RE.SH RestrictionsIn line-by-line mode, the terminal's EOF character is only recognized andsent to the remote system when it is the first character on a line.