1.\" $NetBSD: telnet.1,v 1.13 1999/07/28 06:35:16 abs Exp $ 2.\" 3.\" Copyright (c) 1983, 1990, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" from: @(#)telnet.1 8.4 (Berkeley) 2/3/94 35.\" 36.Dd February 3, 1994 37.Dt TELNET 1 38.Os 39.Sh NAME 40.Nm telnet 41.Nd user interface to the 42.Tn TELNET 43protocol 44.Sh SYNOPSIS 45.Nm "" 46.Op Fl 8 47.Op Fl E 48.Op Fl F 49.Op Fl K 50.Op Fl L 51.Op Fl N 52.Bk -words 53.Op Fl S Ar tos 54.Ek 55.Bk -words 56.Op Fl X Ar authtype 57.Ek 58.Op Fl a 59.Op Fl c 60.Op Fl d 61.Bk -words 62.Op Fl e Ar escapechar 63.Ek 64.Op Fl f 65.Bk -words 66.Op Fl k Ar realm 67.Ek 68.Bk -words 69.Op Fl l Ar user 70.Ek 71.Bk -words 72.Op Fl n Ar tracefile 73.Ek 74.Bk -words 75.Op Fl P Ar policy 76.Ek 77.Op Fl r 78.Op Fl x 79.Oo 80.Ar host 81.Op Ar port 82.Oc 83.Sh DESCRIPTION 84The 85.Nm telnet 86command 87is used to communicate with another host using the 88.Tn TELNET 89protocol. 90If 91.Nm telnet 92is invoked without the 93.Ar host 94argument, it enters command mode, 95indicated by its prompt 96.Pq Nm telnet\&> . 97In this mode, it accepts and executes the commands listed below. 98If it is invoked with arguments, it performs an 99.Ic open 100command with those arguments. 101.Pp 102Options: 103.Bl -tag -width indent 104.It Fl 8 105Specifies an 8-bit data path. This causes an attempt to 106negotiate the 107.Dv TELNET BINARY 108option on both input and output. 109.It Fl E 110Stops any character from being recognized as an escape character. 111.It Fl F 112If Kerberos V5 authentication is being used, the 113.Fl F 114option allows the local credentials to be forwarded 115to the remote system, including any credentials that 116have already been forwarded into the local environment. 117.It Fl K 118Specifies no automatic login to the remote system. 119.It Fl L 120Specifies an 8-bit data path on output. This causes the 121BINARY option to be negotiated on output. 122.It Fl N 123Numeric host address. No attempt will be made to look up 124symbolic names for host addresses. 125.It Fl S Ar tos 126Sets the IP type-of-service (TOS) option for the telnet 127connection to the value 128.Ar tos, 129which can be a numeric TOS value 130or, on systems that support it, a symbolic 131TOS name found in the /etc/iptos file. 132.It Fl X Ar atype 133Disables the 134.Ar atype 135type of authentication. 136.It Fl a 137Attempt automatic login. 138Currently, this sends the user name via the 139.Ev USER 140variable 141of the 142.Ev ENVIRON 143option if supported by the remote system. 144The name used is that of the current user as returned by 145.Xr getlogin 2 146if it agrees with the current user ID, 147otherwise it is the name associated with the user ID. 148.It Fl c 149Disables the reading of the user's 150.Pa \&.telnetrc 151file. (See the 152.Ic toggle skiprc 153command on this man page.) 154.It Fl d 155Sets the initial value of the 156.Ic debug 157toggle to 158.Dv TRUE . 159.It Fl e Ar escape char 160Sets the initial 161.Nm telnet 162escape character to 163.Ar escape char . 164If 165.Ar escape char 166is omitted, then 167there will be no escape character. 168.It Fl f 169If Kerberos V5 authentication is being used, the 170.Fl f 171option allows the local credentials to be forwarded to the remote system. 172.It Fl k Ar realm 173If Kerberos authentication is being used, the 174.Fl k 175option requests that telnet obtain tickets for the remote host in 176realm 177.Ar realm 178instead of the remote host's realm, as determined by 179.Xr krb_realmofhost 3 . 180.It Fl l Ar user 181When connecting to the remote system, if the remote system 182understands the 183.Ev ENVIRON 184option, then 185.Ar user 186will be sent to the remote system as the value for the variable USER. 187This option implies the 188.Fl a 189option. 190This option may also be used with the 191.Ic open 192command. 193.It Fl n Ar tracefile 194Opens 195.Ar tracefile 196for recording trace information. 197See the 198.Ic set tracefile 199command below. 200.It Fl P Ar policy 201Use IPsec policy specification string 202.Ar policy , 203for the connections. 204See 205.Xr ipsec_set_policy 3 206for details. 207.It Fl r 208Specifies a user interface similar to 209.Xr rlogin 1 . 210In this 211mode, the escape character is set to the tilde (~) character, 212unless modified by the 213.Fl e 214option. 215.It Fl x 216Turns on encryption of the data stream if possible. This 217option is not available outside of the United States and 218Canada. 219.It Ar host 220Indicates the official name, an alias, or the Internet address 221of a remote host. 222.It Ar port 223Indicates a port number (address of an application). If a number is 224not specified, the default 225.Nm telnet 226port is used. 227.El 228.Pp 229When in rlogin mode, a line of the form ~. disconnects from the 230remote host; ~ is the telnet escape character. 231Similarly, the line ~^Z suspends the telnet session. 232The line ~^] escapes to the normal telnet escape prompt. 233.Pp 234Once a connection has been opened, 235.Nm telnet 236will attempt to enable the 237.Dv TELNET LINEMODE 238option. 239If this fails, then 240.Nm telnet 241will revert to one of two input modes: 242either \*(Lqcharacter at a time\*(Rq 243or \*(Lqold line by line\*(Rq 244depending on what the remote system supports. 245.Pp 246When 247.Dv LINEMODE 248is enabled, character processing is done on the 249local system, under the control of the remote system. When input 250editing or character echoing is to be disabled, the remote system 251will relay that information. The remote system will also relay 252changes to any special characters that happen on the remote 253system, so that they can take effect on the local system. 254.Pp 255In \*(Lqcharacter at a time\*(Rq mode, most 256text typed is immediately sent to the remote host for processing. 257.Pp 258In \*(Lqold line by line\*(Rq mode, all text is echoed locally, 259and (normally) only completed lines are sent to the remote host. 260The \*(Lqlocal echo character\*(Rq (initially \*(Lq^E\*(Rq) may be used 261to turn off and on the local echo 262(this would mostly be used to enter passwords 263without the password being echoed). 264.Pp 265If the 266.Dv LINEMODE 267option is enabled, or if the 268.Ic localchars 269toggle is 270.Dv TRUE 271(the default for \*(Lqold line by line\*(Lq; see below), 272the user's 273.Ic quit , 274.Ic intr , 275and 276.Ic flush 277characters are trapped locally, and sent as 278.Tn TELNET 279protocol sequences to the remote side. 280If 281.Dv LINEMODE 282has ever been enabled, then the user's 283.Ic susp 284and 285.Ic eof 286are also sent as 287.Tn TELNET 288protocol sequences, 289and 290.Ic quit 291is sent as a 292.Dv TELNET ABORT 293instead of 294.Dv BREAK . 295There are options (see 296.Ic toggle 297.Ic autoflush 298and 299.Ic toggle 300.Ic autosynch 301below) 302which cause this action to flush subsequent output to the terminal 303(until the remote host acknowledges the 304.Tn TELNET 305sequence) and flush previous terminal input 306(in the case of 307.Ic quit 308and 309.Ic intr ) . 310.Pp 311While connected to a remote host, 312.Nm telnet 313command mode may be entered by typing the 314.Nm telnet 315\*(Lqescape character\*(Rq (initially \*(Lq^]\*(Rq). 316When in command mode, the normal terminal editing conventions are available. 317.Pp 318The following 319.Nm telnet 320commands are available. 321Only enough of each command to uniquely identify it need be typed 322(this is also true for arguments to the 323.Ic mode , 324.Ic set , 325.Ic toggle , 326.Ic unset , 327.Ic slc , 328.Ic environ , 329and 330.Ic display 331commands). 332.Pp 333.Bl -tag -width "mode type" 334.It Ic auth Ar argument ... 335The auth command manipulates the information sent through the 336.Dv TELNET AUTHENTICATE 337option. Valid arguments for the 338auth command are as follows: 339.Bl -tag -width "disable type" 340.It Ic disable Ar type 341Disables the specified type of authentication. To 342obtain a list of available types, use the 343.Ic auth disable \&? 344command. 345.It Ic enable Ar type 346Enables the specified type of authentication. To 347obtain a list of available types, use the 348.Ic auth enable \&? 349command. 350.It Ic status 351Lists the current status of the various types of 352authentication. 353.El 354.It Ic close 355Close a 356.Tn TELNET 357session and return to command mode. 358.It Ic display Ar argument ... 359Displays all, or some, of the 360.Ic set 361and 362.Ic toggle 363values (see below). 364.It Ic encrypt Ar argument ... 365The encrypt command manipulates the information sent through the 366.Dv TELNET ENCRYPT 367option. 368.Pp 369Note: Because of export controls, the 370.Dv TELNET ENCRYPT 371option is not supported outside of the United States and Canada. 372.Pp 373Valid arguments for the encrypt command are: 374.Bl -tag -width Ar 375.It Ic disable Ar type Ic [input|output] 376Disables the specified type of encryption. If you 377omit the input and output, both input and output 378are disabled. To obtain a list of available 379types, use the 380.Ic encrypt disable \&? 381command. 382.It Ic enable Ar type Ic [input|output] 383Enables the specified type of encryption. If you 384omit input and output, both input and output are 385enabled. To obtain a list of available types, use the 386.Ic encrypt enable \&? 387command. 388.It Ic input 389This is the same as the 390.Ic encrypt start input 391command. 392.It Ic -input 393This is the same as the 394.Ic encrypt stop input 395command. 396.It Ic output 397This is the same as the 398.Ic encrypt start output 399command. 400.It Ic -output 401This is the same as the 402.Ic encrypt stop output 403command. 404.It Ic start Ic [input|output] 405Attempts to start encryption. If you omit 406.Ic input 407and 408.Ic output, 409both input and output are enabled. To 410obtain a list of available types, use the 411.Ic encrypt enable \&? 412command. 413.It Ic status 414Lists the current status of encryption. 415.It Ic stop Ic [input|output] 416Stops encryption. If you omit input and output, 417encryption is on both input and output. 418.It Ic type Ar type 419Sets the default type of encryption to be used 420with later 421.Ic encrypt start 422or 423.Ic encrypt stop 424commands. 425.El 426.It Ic environ Ar arguments... 427The 428.Ic environ 429command is used to manipulate the 430variables that may be sent through the 431.Dv TELNET ENVIRON 432option. 433The initial set of variables is taken from the users 434environment, with only the 435.Ev DISPLAY 436and 437.Ev PRINTER 438variables being exported by default. 439The 440.Ev USER 441variable is also exported if the 442.Fl a 443or 444.Fl l 445options are used. 446.Pp 447Valid arguments for the 448.Ic environ 449command are: 450.Bl -tag -width Fl 451.It Ic define Ar variable value 452Define the variable 453.Ar variable 454to have a value of 455.Ar value. 456Any variables defined by this command are automatically exported. 457The 458.Ar value 459may be enclosed in single or double quotes so 460that tabs and spaces may be included. 461.It Ic undefine Ar variable 462Remove 463.Ar variable 464from the list of environment variables. 465.It Ic export Ar variable 466Mark the variable 467.Ar variable 468to be exported to the remote side. 469.It Ic unexport Ar variable 470Mark the variable 471.Ar variable 472to not be exported unless 473explicitly asked for by the remote side. 474.It Ic list 475List the current set of environment variables. 476Those marked with a 477.Cm * 478will be sent automatically, 479other variables will only be sent if explicitly requested. 480.It Ic \&? 481Prints out help information for the 482.Ic environ 483command. 484.El 485.It Ic logout 486Sends the 487.Dv TELNET LOGOUT 488option to the remote side. 489This command is similar to a 490.Ic close 491command; however, if the remote side does not support the 492.Dv LOGOUT 493option, nothing happens. 494If, however, the remote side does support the 495.Dv LOGOUT 496option, this command should cause the remote side to close the 497.Tn TELNET 498connection. 499If the remote side also supports the concept of 500suspending a user's session for later reattachment, 501the logout argument indicates that you 502should terminate the session immediately. 503.It Ic mode Ar type 504.Ar Type 505is one of several options, depending on the state of the 506.Tn TELNET 507session. 508The remote host is asked for permission to go into the requested mode. 509If the remote host is capable of entering that mode, the requested 510mode will be entered. 511.Bl -tag -width Ar 512.It Ic character 513Disable the 514.Dv TELNET LINEMODE 515option, or, if the remote side does not understand the 516.Dv LINEMODE 517option, then enter \*(Lqcharacter at a time\*(Lq mode. 518.It Ic line 519Enable the 520.Dv TELNET LINEMODE 521option, or, if the remote side does not understand the 522.Dv LINEMODE 523option, then attempt to enter \*(Lqold-line-by-line\*(Lq mode. 524.It Ic isig Pq Ic \-isig 525Attempt to enable (disable) the 526.Dv TRAPSIG 527mode of the 528.Dv LINEMODE 529option. 530This requires that the 531.Dv LINEMODE 532option be enabled. 533.It Ic edit Pq Ic \-edit 534Attempt to enable (disable) the 535.Dv EDIT 536mode of the 537.Dv LINEMODE 538option. 539This requires that the 540.Dv LINEMODE 541option be enabled. 542.It Ic softtabs Pq Ic \-softtabs 543Attempt to enable (disable) the 544.Dv SOFT_TAB 545mode of the 546.Dv LINEMODE 547option. 548This requires that the 549.Dv LINEMODE 550option be enabled. 551.It Ic litecho Pq Ic \-litecho 552Attempt to enable (disable) the 553.Dv LIT_ECHO 554mode of the 555.Dv LINEMODE 556option. 557This requires that the 558.Dv LINEMODE 559option be enabled. 560.It Ic \&? 561Prints out help information for the 562.Ic mode 563command. 564.El 565.It Xo 566.Ic open Ar host 567.Op Fl l Ar user 568.Op Fl a 569.Oo Op \&- Ns 570.Ar port Oc 571.Xc 572Open a connection to the named host. 573If no port number 574is specified, 575.Nm telnet 576will attempt to contact a 577.Tn TELNET 578server at the default port. 579The host specification may be either a host name (see 580.Xr hosts 5 ) 581or an Internet address specified in the \*(Lqdot notation\*(Rq (see 582.Xr inet 3 ) . 583The 584.Fl l 585option may be used to specify the user name 586to be passed to the remote system via the 587.Ev ENVIRON 588option. 589When connecting to a non-standard port, 590.Nm telnet 591omits any automatic initiation of 592.Tn TELNET 593options. When the port number is preceded by a minus sign, 594the initial option negotiation is done. 595After establishing a connection, the file 596.Pa \&.telnetrc 597in the 598user's home directory is opened. Lines beginning with a # are 599comment lines. Blank lines are ignored. Lines that begin 600without white space are the start of a machine entry. The 601first thing on the line is the name of the machine that is 602being connected to. The rest of the line, and successive 603lines that begin with white space are assumed to be 604.Nm telnet 605commands and are processed as if they had been typed 606in manually to the 607.Nm telnet 608command prompt. 609.It Ic quit 610Close any open 611.Tn TELNET 612session and exit 613.Nm telnet . 614An end of file (in command mode) will also close a session and exit. 615.It Ic send Ar arguments 616Sends one or more special character sequences to the remote host. 617The following are the arguments which may be specified 618(more than one argument may be specified at a time): 619.Pp 620.Bl -tag -width escape 621.It Ic abort 622Sends the 623.Dv TELNET ABORT 624(Abort 625processes) 626sequence. 627.It Ic ao 628Sends the 629.Dv TELNET AO 630(Abort Output) sequence, which should cause the remote system to flush 631all output 632.Em from 633the remote system 634.Em to 635the user's terminal. 636.It Ic ayt 637Sends the 638.Dv TELNET AYT 639(Are You There) 640sequence, to which the remote system may or may not choose to respond. 641.It Ic brk 642Sends the 643.Dv TELNET BRK 644(Break) sequence, which may have significance to the remote 645system. 646.It Ic ec 647Sends the 648.Dv TELNET EC 649(Erase Character) 650sequence, which should cause the remote system to erase the last character 651entered. 652.It Ic el 653Sends the 654.Dv TELNET EL 655(Erase Line) 656sequence, which should cause the remote system to erase the line currently 657being entered. 658.It Ic eof 659Sends the 660.Dv TELNET EOF 661(End Of File) 662sequence. 663.It Ic eor 664Sends the 665.Dv TELNET EOR 666(End of Record) 667sequence. 668.It Ic escape 669Sends the current 670.Nm telnet 671escape character (initially \*(Lq^\*(Rq). 672.It Ic ga 673Sends the 674.Dv TELNET GA 675(Go Ahead) 676sequence, which likely has no significance to the remote system. 677.It Ic getstatus 678If the remote side supports the 679.Dv TELNET STATUS 680command, 681.Ic getstatus 682will send the subnegotiation to request that the server send 683its current option status. 684.It Ic ip 685Sends the 686.Dv TELNET IP 687(Interrupt Process) sequence, which should cause the remote 688system to abort the currently running process. 689.It Ic nop 690Sends the 691.Dv TELNET NOP 692(No OPeration) 693sequence. 694.It Ic susp 695Sends the 696.Dv TELNET SUSP 697(SUSPend process) 698sequence. 699.It Ic synch 700Sends the 701.Dv TELNET SYNCH 702sequence. 703This sequence causes the remote system to discard all previously typed 704(but not yet read) input. 705This sequence is sent as 706.Tn TCP 707urgent 708data (and may not work if the remote system is a 709.Bx 4.2 710system -- if 711it doesn't work, a lower case \*(Lqr\*(Rq may be echoed on the terminal). 712.It Ic do Ar cmd 713.It Ic dont Ar cmd 714.It Ic will Ar cmd 715.It Ic wont Ar cmd 716Sends the 717.Dv TELNET DO 718.Ar cmd 719sequence. 720.Ar Cmd 721can be either a decimal number between 0 and 255, 722or a symbolic name for a specific 723.Dv TELNET 724command. 725.Ar Cmd 726can also be either 727.Ic help 728or 729.Ic \&? 730to print out help information, including 731a list of known symbolic names. 732.It Ic \&? 733Prints out help information for the 734.Ic send 735command. 736.El 737.It Ic set Ar argument value 738.It Ic unset Ar argument value 739The 740.Ic set 741command will set any one of a number of 742.Nm telnet 743variables to a specific value or to 744.Dv TRUE . 745The special value 746.Ic off 747turns off the function associated with 748the variable, this is equivalent to using the 749.Ic unset 750command. 751The 752.Ic unset 753command will disable or set to 754.Dv FALSE 755any of the specified functions. 756The values of variables may be interrogated with the 757.Ic display 758command. 759The variables which may be set or unset, but not toggled, are 760listed here. In addition, any of the variables for the 761.Ic toggle 762command may be explicitly set or unset using 763the 764.Ic set 765and 766.Ic unset 767commands. 768.Bl -tag -width escape 769.It Ic ayt 770If 771.Tn TELNET 772is in localchars mode, or 773.Dv LINEMODE 774is enabled, and the status character is typed, a 775.Dv TELNET AYT 776sequence (see 777.Ic send ayt 778above) is sent to the 779remote host. The initial value for the "Are You There" 780character is the terminal's status character. 781.It Ic echo 782This is the value (initially \*(Lq^E\*(Rq) which, when in 783\*(Lqline by line\*(Rq mode, toggles between doing local echoing 784of entered characters (for normal processing), and suppressing 785echoing of entered characters (for entering, say, a password). 786.It Ic eof 787If 788.Nm telnet 789is operating in 790.Dv LINEMODE 791or \*(Lqold line by line\*(Rq mode, entering this character 792as the first character on a line will cause this character to be 793sent to the remote system. 794The initial value of the eof character is taken to be the terminal's 795.Ic eof 796character. 797.It Ic erase 798If 799.Nm telnet 800is in 801.Ic localchars 802mode (see 803.Ic toggle 804.Ic localchars 805below), 806.Sy and 807if 808.Nm telnet 809is operating in \*(Lqcharacter at a time\*(Rq mode, then when this 810character is typed, a 811.Dv TELNET EC 812sequence (see 813.Ic send 814.Ic ec 815above) 816is sent to the remote system. 817The initial value for the erase character is taken to be 818the terminal's 819.Ic erase 820character. 821.It Ic escape 822This is the 823.Nm telnet 824escape character (initially \*(Lq^[\*(Rq) which causes entry 825into 826.Nm telnet 827command mode (when connected to a remote system). 828.It Ic flushoutput 829If 830.Nm telnet 831is in 832.Ic localchars 833mode (see 834.Ic toggle 835.Ic localchars 836below) 837and the 838.Ic flushoutput 839character is typed, a 840.Dv TELNET AO 841sequence (see 842.Ic send 843.Ic ao 844above) 845is sent to the remote host. 846The initial value for the flush character is taken to be 847the terminal's 848.Ic flush 849character. 850.It Ic forw1 851.It Ic forw2 852If 853.Tn TELNET 854is operating in 855.Dv LINEMODE , 856these are the 857characters that, when typed, cause partial lines to be 858forwarded to the remote system. The initial value for 859the forwarding characters are taken from the terminal's 860eol and eol2 characters. 861.It Ic interrupt 862If 863.Nm telnet 864is in 865.Ic localchars 866mode (see 867.Ic toggle 868.Ic localchars 869below) 870and the 871.Ic interrupt 872character is typed, a 873.Dv TELNET IP 874sequence (see 875.Ic send 876.Ic ip 877above) 878is sent to the remote host. 879The initial value for the interrupt character is taken to be 880the terminal's 881.Ic intr 882character. 883.It Ic kill 884If 885.Nm telnet 886is in 887.Ic localchars 888mode (see 889.Ic toggle 890.Ic localchars 891below), 892.Ic and 893if 894.Nm telnet 895is operating in \*(Lqcharacter at a time\*(Rq mode, then when this 896character is typed, a 897.Dv TELNET EL 898sequence (see 899.Ic send 900.Ic el 901above) 902is sent to the remote system. 903The initial value for the kill character is taken to be 904the terminal's 905.Ic kill 906character. 907.It Ic lnext 908If 909.Nm telnet 910is operating in 911.Dv LINEMODE 912or \*(Lqold line by line\*(Lq mode, then this character is taken to 913be the terminal's 914.Ic lnext 915character. 916The initial value for the lnext character is taken to be 917the terminal's 918.Ic lnext 919character. 920.It Ic quit 921If 922.Nm telnet 923is in 924.Ic localchars 925mode (see 926.Ic toggle 927.Ic localchars 928below) 929and the 930.Ic quit 931character is typed, a 932.Dv TELNET BRK 933sequence (see 934.Ic send 935.Ic brk 936above) 937is sent to the remote host. 938The initial value for the quit character is taken to be 939the terminal's 940.Ic quit 941character. 942.It Ic reprint 943If 944.Nm telnet 945is operating in 946.Dv LINEMODE 947or \*(Lqold line by line\*(Lq mode, then this character is taken to 948be the terminal's 949.Ic reprint 950character. 951The initial value for the reprint character is taken to be 952the terminal's 953.Ic reprint 954character. 955.It Ic rlogin 956This is the rlogin escape character. 957If set, the normal 958.Tn TELNET 959escape character is ignored unless it is 960preceded by this character at the beginning of a line. 961This character, at the beginning of a line followed by 962a "." closes the connection; when followed by a ^Z it 963suspends the 964.Nm telnet 965command. The initial state is to 966disable the rlogin escape character. 967.It Ic start 968If the 969.Dv TELNET TOGGLE-FLOW-CONTROL 970option has been enabled, 971then this character is taken to 972be the terminal's 973.Ic start 974character. 975The initial value for the start character is taken to be 976the terminal's 977.Ic start 978character. 979.It Ic stop 980If the 981.Dv TELNET TOGGLE-FLOW-CONTROL 982option has been enabled, 983then this character is taken to 984be the terminal's 985.Ic stop 986character. 987The initial value for the stop character is taken to be 988the terminal's 989.Ic stop 990character. 991.It Ic susp 992If 993.Nm telnet 994is in 995.Ic localchars 996mode, or 997.Dv LINEMODE 998is enabled, and the 999.Ic suspend 1000character is typed, a 1001.Dv TELNET SUSP 1002sequence (see 1003.Ic send 1004.Ic susp 1005above) 1006is sent to the remote host. 1007The initial value for the suspend character is taken to be 1008the terminal's 1009.Ic suspend 1010character. 1011.It Ic tracefile 1012This is the file to which the output, caused by 1013.Ic netdata 1014or 1015.Ic option 1016tracing being 1017.Dv TRUE , 1018will be written. If it is set to 1019.Dq Fl , 1020then tracing information will be written to standard output (the default). 1021.It Ic worderase 1022If 1023.Nm telnet 1024is operating in 1025.Dv LINEMODE 1026or \*(Lqold line by line\*(Lq mode, then this character is taken to 1027be the terminal's 1028.Ic worderase 1029character. 1030The initial value for the worderase character is taken to be 1031the terminal's 1032.Ic worderase 1033character. 1034.It Ic \&? 1035Displays the legal 1036.Ic set 1037.Pq Ic unset 1038commands. 1039.El 1040.It Ic slc Ar state 1041The 1042.Ic slc 1043command (Set Local Characters) is used to set 1044or change the state of the special 1045characters when the 1046.Dv TELNET LINEMODE 1047option has 1048been enabled. Special characters are characters that get 1049mapped to 1050.Tn TELNET 1051commands sequences (like 1052.Ic ip 1053or 1054.Ic quit ) 1055or line editing characters (like 1056.Ic erase 1057and 1058.Ic kill ) . 1059By default, the local special characters are exported. 1060.Bl -tag -width Fl 1061.It Ic check 1062Verify the current settings for the current special characters. 1063The remote side is requested to send all the current special 1064character settings, and if there are any discrepancies with 1065the local side, the local side will switch to the remote value. 1066.It Ic export 1067Switch to the local defaults for the special characters. The 1068local default characters are those of the local terminal at 1069the time when 1070.Nm telnet 1071was started. 1072.It Ic import 1073Switch to the remote defaults for the special characters. 1074The remote default characters are those of the remote system 1075at the time when the 1076.Tn TELNET 1077connection was established. 1078.It Ic \&? 1079Prints out help information for the 1080.Ic slc 1081command. 1082.El 1083.It Ic status 1084Show the current status of 1085.Nm telnet . 1086This includes the peer one is connected to, as well 1087as the current mode. 1088.It Ic toggle Ar arguments ... 1089Toggle (between 1090.Dv TRUE 1091and 1092.Dv FALSE ) 1093various flags that control how 1094.Nm telnet 1095responds to events. 1096These flags may be set explicitly to 1097.Dv TRUE 1098or 1099.Dv FALSE 1100using the 1101.Ic set 1102and 1103.Ic unset 1104commands listed above. 1105More than one argument may be specified. 1106The state of these flags may be interrogated with the 1107.Ic display 1108command. 1109Valid arguments are: 1110.Bl -tag -width Ar 1111.It Ic authdebug 1112Turns on debugging information for the authentication code. 1113.It Ic autoflush 1114If 1115.Ic autoflush 1116and 1117.Ic localchars 1118are both 1119.Dv TRUE , 1120then when the 1121.Ic ao , 1122or 1123.Ic quit 1124characters are recognized (and transformed into 1125.Tn TELNET 1126sequences; see 1127.Ic set 1128above for details), 1129.Nm telnet 1130refuses to display any data on the user's terminal 1131until the remote system acknowledges (via a 1132.Dv TELNET TIMING MARK 1133option) 1134that it has processed those 1135.Tn TELNET 1136sequences. 1137The initial value for this toggle is 1138.Dv TRUE 1139if the terminal user had not 1140done an "stty noflsh", otherwise 1141.Dv FALSE 1142(see 1143.Xr stty 1 ) . 1144.It Ic autodecrypt 1145When the 1146.Dv TELNET ENCRYPT 1147option is negotiated, by 1148default the actual encryption (decryption) of the data 1149stream does not start automatically. The autoencrypt 1150(autodecrypt) command states that encryption of the 1151output (input) stream should be enabled as soon as 1152possible. 1153.Pp 1154Note: Because of export controls, the 1155.Dv TELNET ENCRYPT 1156option is not supported outside the United States and Canada. 1157.It Ic autologin 1158If the remote side supports the 1159.Dv TELNET AUTHENTICATION 1160option 1161.Tn TELNET 1162attempts to use it to perform automatic authentication. If the 1163.Dv AUTHENTICATION 1164option is not supported, the user's login 1165name are propagated through the 1166.Dv TELNET ENVIRON 1167option. 1168This command is the same as specifying the 1169.Fl a 1170option on the 1171.Ic open 1172command. 1173.It Ic autosynch 1174If 1175.Ic autosynch 1176and 1177.Ic localchars 1178are both 1179.Dv TRUE , 1180then when either the 1181.Ic intr 1182or 1183.Ic quit 1184characters is typed (see 1185.Ic set 1186above for descriptions of the 1187.Ic intr 1188and 1189.Ic quit 1190characters), the resulting 1191.Tn TELNET 1192sequence sent is followed by the 1193.Dv TELNET SYNCH 1194sequence. 1195This procedure 1196.Ic should 1197cause the remote system to begin throwing away all previously 1198typed input until both of the 1199.Tn TELNET 1200sequences have been read and acted upon. 1201The initial value of this toggle is 1202.Dv FALSE . 1203.It Ic binary 1204Enable or disable the 1205.Dv TELNET BINARY 1206option on both input and output. 1207.It Ic inbinary 1208Enable or disable the 1209.Dv TELNET BINARY 1210option on input. 1211.It Ic outbinary 1212Enable or disable the 1213.Dv TELNET BINARY 1214option on output. 1215.It Ic crlf 1216If this is 1217.Dv TRUE , 1218then carriage returns will be sent as 1219.Li <CR><LF> . 1220If this is 1221.Dv FALSE , 1222then carriage returns will be send as 1223.Li <CR><NUL> . 1224The initial value for this toggle is 1225.Dv FALSE . 1226.It Ic crmod 1227Toggle carriage return mode. 1228When this mode is enabled, most carriage return characters received from 1229the remote host will be mapped into a carriage return followed by 1230a line feed. 1231This mode does not affect those characters typed by the user, only 1232those received from the remote host. 1233This mode is not very useful unless the remote host 1234only sends carriage return, but never line feed. 1235The initial value for this toggle is 1236.Dv FALSE . 1237.It Ic debug 1238Toggles socket level debugging (useful only to the 1239.Ic super user ) . 1240The initial value for this toggle is 1241.Dv FALSE . 1242.It Ic encdebug 1243Turns on debugging information for the encryption code. 1244.It Ic localchars 1245If this is 1246.Dv TRUE , 1247then the 1248.Ic flush , 1249.Ic interrupt , 1250.Ic quit , 1251.Ic erase , 1252and 1253.Ic kill 1254characters (see 1255.Ic set 1256above) are recognized locally, and transformed into (hopefully) appropriate 1257.Tn TELNET 1258control sequences 1259(respectively 1260.Ic ao , 1261.Ic ip , 1262.Ic brk , 1263.Ic ec , 1264and 1265.Ic el ; 1266see 1267.Ic send 1268above). 1269The initial value for this toggle is 1270.Dv TRUE 1271in \*(Lqold line by line\*(Rq mode, 1272and 1273.Dv FALSE 1274in \*(Lqcharacter at a time\*(Rq mode. 1275When the 1276.Dv LINEMODE 1277option is enabled, the value of 1278.Ic localchars 1279is ignored, and assumed to always be 1280.Dv TRUE . 1281If 1282.Dv LINEMODE 1283has ever been enabled, then 1284.Ic quit 1285is sent as 1286.Ic abort , 1287and 1288.Ic eof and 1289.Ic suspend 1290are sent as 1291.Ic eof and 1292.Ic susp 1293(see 1294.Ic send 1295above). 1296.It Ic netdata 1297Toggles the display of all network data (in hexadecimal format). 1298The initial value for this toggle is 1299.Dv FALSE . 1300.It Ic options 1301Toggles the display of some internal 1302.Nm telnet 1303protocol processing (having to do with 1304.Tn TELNET 1305options). 1306The initial value for this toggle is 1307.Dv FALSE . 1308.It Ic prettydump 1309When the 1310.Ic netdata 1311toggle is enabled, if 1312.Ic prettydump 1313is enabled the output from the 1314.Ic netdata 1315command will be formatted in a more user readable format. 1316Spaces are put between each character in the output, and the 1317beginning of any 1318.Tn TELNET 1319escape sequence is preceded by a '*' to aid in locating them. 1320.It Ic skiprc 1321When the skiprc toggle is 1322.Dv TRUE , 1323.Tn TELNET 1324skips the reading of the 1325.Pa \&.telnetrc 1326file in the users home 1327directory when connections are opened. The initial 1328value for this toggle is 1329.Dv FALSE. 1330.It Ic termdata 1331Toggles the display of all terminal data (in hexadecimal format). 1332The initial value for this toggle is 1333.Dv FALSE . 1334.It Ic verbose_encrypt 1335When the 1336.Ic verbose_encrypt 1337toggle is 1338.Dv TRUE , 1339.Nm telnet 1340prints out a message each time encryption is enabled or 1341disabled. The initial value for this toggle is 1342.Dv FALSE. 1343Note: Because of export controls, data encryption 1344is not supported outside of the United States and Canada. 1345.It Ic \&? 1346Displays the legal 1347.Ic toggle 1348commands. 1349.El 1350.It Ic z 1351Suspend 1352.Nm telnet . 1353This command only works when the user is using the 1354.Xr csh 1 . 1355.It Ic \&! Op Ar command 1356Execute a single command in a subshell on the local 1357system. If 1358.Ar command 1359is omitted, then an interactive 1360subshell is invoked. 1361.It Ic \&? Op Ar command 1362Get help. With no arguments, 1363.Nm telnet 1364prints a help summary. 1365If a command is specified, 1366.Nm telnet 1367will print the help information for just that command. 1368.El 1369.Sh ENVIRONMENT 1370.Nm Telnet 1371uses at least the 1372.Ev HOME , 1373.Ev SHELL , 1374.Ev DISPLAY , 1375and 1376.Ev TERM 1377environment variables. 1378Other environment variables may be propagated 1379to the other side via the 1380.Dv TELNET ENVIRON 1381option. 1382.Sh FILES 1383.Bl -tag -width ~/.telnetrc -compact 1384.It Pa ~/.telnetrc 1385user customized telnet startup values 1386.El 1387.Sh HISTORY 1388The 1389.Nm Telnet 1390command appeared in 1391.Bx 4.2 . 1392IPsec support was added by WIDE/KAME project, in 1999. 1393.Sh NOTES 1394.Pp 1395On some remote systems, echo has to be turned off manually when in 1396\*(Lqold line by line\*(Rq mode. 1397.Pp 1398In \*(Lqold line by line\*(Rq mode or 1399.Dv LINEMODE 1400the terminal's 1401.Ic eof 1402character is only recognized (and sent to the remote system) 1403when it is the first character on a line. 1404