1.\" Copyright (c) 1983, 1990, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)telnet.1 8.6 (Berkeley) 6/1/94 29.\" $FreeBSD$ 30.\" 31.Dd June 21, 2021 32.Dt TELNET 1 33.Os 34.Sh NAME 35.Nm telnet 36.Nd user interface to the 37.Tn TELNET 38protocol 39.Sh SYNOPSIS 40.Nm 41.Op Fl 468EFKLNQacdfruxy 42.Op Fl B Ar baudrate 43.Op Fl S Ar tos 44.Op Fl X Ar authtype 45.Op Fl e Ar escapechar 46.Op Fl k Ar realm 47.Op Fl l Ar user 48.Op Fl n Ar tracefile 49.Op Fl s Ar src_addr 50.Op Fl P Ar policy 51.Oo 52.Ar host 53.Op Ar port 54.Oc 55.Sh DESCRIPTION 56The 57.Nm 58command 59is used to communicate with another host using the 60.Tn TELNET 61protocol. 62If 63.Nm 64is invoked without the 65.Ar host 66argument, it enters command mode, 67indicated by its prompt 68.Pq Dq Li telnet\&> . 69In this mode, it accepts and executes the commands listed below. 70If it is invoked with arguments, it performs an 71.Ic open 72command with those arguments. 73.Pp 74Options: 75.Bl -tag -width indent 76.It Fl 4 77Forces 78.Nm 79to use IPv4 addresses only. 80.It Fl 6 81Forces 82.Nm 83to use IPv6 addresses only. 84.It Fl 8 85Specifies an 8-bit data path. 86This causes an attempt to 87negotiate the 88.Dv TELNET BINARY 89option on both input and output. 90.It Fl B Ar baudrate 91Sets the baud rate to 92.Ar baudrate . 93.It Fl E 94Stops any character from being recognized as an escape character. 95.It Fl F 96If Kerberos V5 authentication is being used, the 97.Fl F 98option allows the local credentials to be forwarded 99to the remote system, including any credentials that 100have already been forwarded into the local environment. 101.It Fl K 102Specifies no automatic login to the remote system. 103.It Fl L 104Specifies an 8-bit data path on output. 105This causes the 106.Dv BINARY 107option to be negotiated on output. 108.It Fl N 109Prevents IP address to name lookup when destination host is given 110as an IP address. 111.It Fl Q 112Quiet mode. 113This suppresses the messages 114.Nm 115would normally output upon connecting or disconnecting. 116.It Fl S Ar tos 117Sets the IP type-of-service (TOS) option for the telnet 118connection to the value 119.Ar tos , 120which can be a numeric TOS value 121or, on systems that support it, a symbolic 122TOS name found in the 123.Pa /etc/iptos 124file. 125.It Fl X Ar atype 126Disables the 127.Ar atype 128type of authentication. 129.It Fl a 130Attempt automatic login. 131This is now the default, so this option is ignored. 132Currently, this sends the user name via the 133.Ev USER 134variable 135of the 136.Ev ENVIRON 137option if supported by the remote system. 138The name used is that of the current user as returned by 139.Xr getlogin 2 140if it agrees with the current user ID, 141otherwise it is the name associated with the user ID. 142.It Fl c 143Disables the reading of the user's 144.Pa \&.telnetrc 145file. 146(See the 147.Ic toggle skiprc 148command on this man page.) 149.It Fl d 150Sets the initial value of the 151.Ic debug 152toggle to 153.Dv TRUE . 154.It Fl e Ar escapechar 155Sets the initial 156.Nm 157escape character to 158.Ar escapechar . 159If 160.Ar escapechar 161is omitted, then 162there will be no escape character. 163.It Fl f 164If Kerberos V5 authentication is being used, the 165.Fl f 166option allows the local credentials to be forwarded to the remote system. 167.It Fl k Ar realm 168If Kerberos authentication is being used, the 169.Fl k 170option requests that 171.Nm 172obtain tickets for the remote host in 173realm 174.Ar realm 175instead of the remote host's realm, as determined by 176.Xr krb_realmofhost 3 . 177.It Fl l Ar user 178When connecting to the remote system, if the remote system 179understands the 180.Ev ENVIRON 181option, then 182.Ar user 183will be sent to the remote system as the value for the variable 184.Ev USER . 185This option implies the 186.Fl a 187option. 188This option may also be used with the 189.Ic open 190command. 191.It Fl n Ar tracefile 192Opens 193.Ar tracefile 194for recording trace information. 195See the 196.Ic set tracefile 197command below. 198.It Fl P Ar policy 199Use IPsec policy specification string 200.Ar policy , 201for the connections. 202See 203.Xr ipsec_set_policy 3 204for details. 205.It Fl r 206Specifies a user interface similar to 207.Xr rlogin 1 . 208In this 209mode, the escape character is set to the tilde (~) character, 210unless modified by the 211.Fl e 212option. 213.It Fl s Ar src_addr 214Set the source IP address for the 215.Nm 216connection to 217.Ar src_addr , 218which can be an IP address or a host name. 219.It Fl u 220Forces 221.Nm 222to use 223.Dv AF_UNIX 224addresses only (e.g., 225.Ux 226domain sockets, accessed with a file path). 227.It Fl x 228Turns on encryption of the data stream if possible. 229This is now the default, so this option is ignored. 230.It Fl y 231Suppresses encryption of the data stream. 232.It Ar host 233Indicates the official name, an alias, or the Internet address 234of a remote host. 235If 236.Ar host 237starts with a 238.Ql / , 239.Nm 240establishes a connection to the corresponding named socket. 241.It Ar port 242Indicates a port number (address of an application). 243If a number is 244not specified, the default 245.Nm 246port is used. 247.El 248.Pp 249When in rlogin mode, a line of the form ~.\& disconnects from the 250remote host; ~ is the 251.Nm 252escape character. 253Similarly, the line ~^Z suspends the 254.Nm 255session. 256The line ~^] escapes to the normal 257.Nm 258escape prompt. 259.Pp 260Once a connection has been opened, 261.Nm 262will attempt to enable the 263.Dv TELNET LINEMODE 264option. 265If this fails, then 266.Nm 267will revert to one of two input modes: 268either \*(Lqcharacter at a time\*(Rq 269or \*(Lqold line by line\*(Rq 270depending on what the remote system supports. 271.Pp 272When 273.Dv LINEMODE 274is enabled, character processing is done on the 275local system, under the control of the remote system. 276When input 277editing or character echoing is to be disabled, the remote system 278will relay that information. 279The remote system will also relay 280changes to any special characters that happen on the remote 281system, so that they can take effect on the local system. 282.Pp 283In \*(Lqcharacter at a time\*(Rq mode, most 284text typed is immediately sent to the remote host for processing. 285.Pp 286In \*(Lqold line by line\*(Rq mode, all text is echoed locally, 287and (normally) only completed lines are sent to the remote host. 288The \*(Lqlocal echo character\*(Rq (initially \*(Lq^E\*(Rq) may be used 289to turn off and on the local echo 290(this would mostly be used to enter passwords 291without the password being echoed). 292.Pp 293If the 294.Dv LINEMODE 295option is enabled, or if the 296.Ic localchars 297toggle is 298.Dv TRUE 299(the default for \*(Lqold line by line\*(Rq; see below), 300the user's 301.Ic quit , 302.Ic intr , 303and 304.Ic flush 305characters are trapped locally, and sent as 306.Tn TELNET 307protocol sequences to the remote side. 308If 309.Dv LINEMODE 310has ever been enabled, then the user's 311.Ic susp 312and 313.Ic eof 314are also sent as 315.Tn TELNET 316protocol sequences, 317and 318.Ic quit 319is sent as a 320.Dv TELNET ABORT 321instead of 322.Dv BREAK . 323There are options (see 324.Ic toggle 325.Ic autoflush 326and 327.Ic toggle 328.Ic autosynch 329below) 330which cause this action to flush subsequent output to the terminal 331(until the remote host acknowledges the 332.Tn TELNET 333sequence) and flush previous terminal input 334(in the case of 335.Ic quit 336and 337.Ic intr ) . 338.Pp 339While connected to a remote host, 340.Nm 341command mode may be entered by typing the 342.Nm 343\*(Lqescape character\*(Rq (initially \*(Lq^]\*(Rq). 344When in command mode, the normal terminal editing conventions are available. 345.Pp 346The following 347.Nm 348commands are available. 349Only enough of each command to uniquely identify it need be typed 350(this is also true for arguments to the 351.Ic mode , 352.Ic set , 353.Ic toggle , 354.Ic unset , 355.Ic slc , 356.Ic environ , 357and 358.Ic display 359commands). 360.Bl -tag -width "mode type" 361.It Ic auth Ar argument ... 362The auth command manipulates the information sent through the 363.Dv TELNET AUTHENTICATE 364option. 365Valid arguments for the 366.Ic auth 367command are: 368.Bl -tag -width "disable type" 369.It Ic disable Ar type 370Disables the specified type of authentication. 371To 372obtain a list of available types, use the 373.Ic auth disable ?\& 374command. 375.It Ic enable Ar type 376Enables the specified type of authentication. 377To 378obtain a list of available types, use the 379.Ic auth enable ?\& 380command. 381.It Ic status 382Lists the current status of the various types of 383authentication. 384.El 385.It Ic close 386Close a 387.Tn TELNET 388session and return to command mode. 389.It Ic display Ar argument ... 390Displays all, or some, of the 391.Ic set 392and 393.Ic toggle 394values (see below). 395.It Ic encrypt Ar argument ... 396The encrypt command manipulates the information sent through the 397.Dv TELNET ENCRYPT 398option. 399.Pp 400Valid arguments for the 401.Ic encrypt 402command are: 403.Bl -tag -width Ar 404.It Ic disable Ar type Xo 405.Op Cm input | output 406.Xc 407Disables the specified type of encryption. 408If you 409omit the input and output, both input and output 410are disabled. 411To obtain a list of available 412types, use the 413.Ic encrypt disable ?\& 414command. 415.It Ic enable Ar type Xo 416.Op Cm input | output 417.Xc 418Enables the specified type of encryption. 419If you 420omit input and output, both input and output are 421enabled. 422To obtain a list of available types, use the 423.Ic encrypt enable ?\& 424command. 425.It Ic input 426This is the same as the 427.Ic encrypt start input 428command. 429.It Ic -input 430This is the same as the 431.Ic encrypt stop input 432command. 433.It Ic output 434This is the same as the 435.Ic encrypt start output 436command. 437.It Ic -output 438This is the same as the 439.Ic encrypt stop output 440command. 441.It Ic start Op Cm input | output 442Attempts to start encryption. 443If you omit 444.Ic input 445and 446.Ic output , 447both input and output are enabled. 448To 449obtain a list of available types, use the 450.Ic encrypt enable ?\& 451command. 452.It Ic status 453Lists the current status of encryption. 454.It Ic stop Op Cm input | output 455Stops encryption. 456If you omit input and output, 457encryption is on both input and output. 458.It Ic type Ar type 459Sets the default type of encryption to be used 460with later 461.Ic encrypt start 462or 463.Ic encrypt stop 464commands. 465.El 466.It Ic environ Ar arguments ... 467The 468.Ic environ 469command is used to manipulate the 470variables that may be sent through the 471.Dv TELNET ENVIRON 472option. 473The initial set of variables is taken from the users 474environment, with only the 475.Ev DISPLAY 476and 477.Ev PRINTER 478variables being exported by default. 479The 480.Ev USER 481variable is also exported if the 482.Fl a 483or 484.Fl l 485options are used. 486.Pp 487Valid arguments for the 488.Ic environ 489command are: 490.Bl -tag -width Fl 491.It Ic define Ar variable value 492Define the variable 493.Ar variable 494to have a value of 495.Ar value . 496Any variables defined by this command are automatically exported. 497The 498.Ar value 499may be enclosed in single or double quotes so 500that tabs and spaces may be included. 501.It Ic undefine Ar variable 502Remove 503.Ar variable 504from the list of environment variables. 505.It Ic export Ar variable 506Mark the variable 507.Ar variable 508to be exported to the remote side. 509.It Ic unexport Ar variable 510Mark the variable 511.Ar variable 512to not be exported unless 513explicitly asked for by the remote side. 514.It Ic list 515List the current set of environment variables. 516Those marked with a 517.Cm * 518will be sent automatically, 519other variables will only be sent if explicitly requested. 520.It Ic ?\& 521Prints out help information for the 522.Ic environ 523command. 524.El 525.It Ic logout 526Sends the 527.Dv TELNET LOGOUT 528option to the remote side. 529This command is similar to a 530.Ic close 531command; however, if the remote side does not support the 532.Dv LOGOUT 533option, nothing happens. 534If, however, the remote side does support the 535.Dv LOGOUT 536option, this command should cause the remote side to close the 537.Tn TELNET 538connection. 539If the remote side also supports the concept of 540suspending a user's session for later reattachment, 541the logout argument indicates that you 542should terminate the session immediately. 543.It Ic mode Ar type 544.Ar Type 545is one of several options, depending on the state of the 546.Tn TELNET 547session. 548The remote host is asked for permission to go into the requested mode. 549If the remote host is capable of entering that mode, the requested 550mode will be entered. 551.Bl -tag -width Ar 552.It Ic character 553Disable the 554.Dv TELNET LINEMODE 555option, or, if the remote side does not understand the 556.Dv LINEMODE 557option, then enter \*(Lqcharacter at a time\*(Rq mode. 558.It Ic line 559Enable the 560.Dv TELNET LINEMODE 561option, or, if the remote side does not understand the 562.Dv LINEMODE 563option, then attempt to enter \*(Lqold-line-by-line\*(Rq mode. 564.It Ic isig Pq Ic \-isig 565Attempt to enable (disable) the 566.Dv TRAPSIG 567mode of the 568.Dv LINEMODE 569option. 570This requires that the 571.Dv LINEMODE 572option be enabled. 573.It Ic edit Pq Ic \-edit 574Attempt to enable (disable) the 575.Dv EDIT 576mode of the 577.Dv LINEMODE 578option. 579This requires that the 580.Dv LINEMODE 581option be enabled. 582.It Ic softtabs Pq Ic \-softtabs 583Attempt to enable (disable) the 584.Dv SOFT_TAB 585mode of the 586.Dv LINEMODE 587option. 588This requires that the 589.Dv LINEMODE 590option be enabled. 591.It Ic litecho Pq Ic \-litecho 592Attempt to enable (disable) the 593.Dv LIT_ECHO 594mode of the 595.Dv LINEMODE 596option. 597This requires that the 598.Dv LINEMODE 599option be enabled. 600.It Ic ?\& 601Prints out help information for the 602.Ic mode 603command. 604.El 605.It Xo 606.Ic open 607.Op Fl l Ar user 608.Op Ar host 609.Op Oo Fl /+ Oc Ns Ar port 610.Xc 611Open a connection to the named host. 612If no port number 613is specified, 614.Nm 615will attempt to contact a 616.Tn TELNET 617server at the default port. 618The host specification may be either a host name (see 619.Xr hosts 5 ) , 620an Internet address specified in the \*(Lqdot notation\*(Rq (see 621.Xr inet 3 ) , 622or IPv6 host name or IPv6 coloned-hexadecimal addreess. 623The 624.Fl l 625option may be used to specify the user name 626to be passed to the remote system via the 627.Ev ENVIRON 628option. 629When connecting to a non-standard port, 630.Nm 631omits any automatic initiation of 632.Tn TELNET 633options. 634When the port number is preceded by a minus sign, 635the initial option negotiation is done. 636When, however, the port number 637is preceded by a plus sign, 638any option negotiation and understanding is prohibited, 639making telnet dumb client for POP3/SMTP/NNTP/HTTP-like 640protocols with any data including 641.Tn TELNET 642IAC character (0xff). 643After establishing a connection, the file 644.Pa \&.telnetrc 645in the 646users home directory is opened. 647Lines beginning with a # are 648comment lines. 649Blank lines are ignored. 650Lines that begin 651without white space are the start of a machine entry. 652The 653first thing on the line is the name of the machine that is 654being connected to. 655It may be the hostname or numeric address specified as the argument 656.Ar host , 657the canonical name of that string as determined by 658.Xr getaddrinfo 3 , 659or the string 660.Dq Li DEFAULT 661indicating all hosts. 662The rest of the line, and successive 663lines that begin with white space are assumed to be 664.Nm 665commands and are processed as if they had been typed 666in manually to the 667.Nm 668command prompt. 669.It Ic quit 670Close any open 671.Tn TELNET 672session and exit 673.Nm . 674An end of file (in command mode) will also close a session and exit. 675.It Ic send Ar arguments 676Sends one or more special character sequences to the remote host. 677The following are the arguments which may be specified 678(more than one argument may be specified at a time): 679.Bl -tag -width escape 680.It Ic abort 681Sends the 682.Dv TELNET ABORT 683(Abort 684processes) 685sequence. 686.It Ic ao 687Sends the 688.Dv TELNET AO 689(Abort Output) sequence, which should cause the remote system to flush 690all output 691.Em from 692the remote system 693.Em to 694the user's terminal. 695.It Ic ayt 696Sends the 697.Dv TELNET AYT 698(Are You There) 699sequence, to which the remote system may or may not choose to respond. 700.It Ic brk 701Sends the 702.Dv TELNET BRK 703(Break) sequence, which may have significance to the remote 704system. 705.It Ic ec 706Sends the 707.Dv TELNET EC 708(Erase Character) 709sequence, which should cause the remote system to erase the last character 710entered. 711.It Ic el 712Sends the 713.Dv TELNET EL 714(Erase Line) 715sequence, which should cause the remote system to erase the line currently 716being entered. 717.It Ic eof 718Sends the 719.Dv TELNET EOF 720(End Of File) 721sequence. 722.It Ic eor 723Sends the 724.Dv TELNET EOR 725(End of Record) 726sequence. 727.It Ic escape 728Sends the current 729.Nm 730escape character (initially \*(Lq^\*(Rq). 731.It Ic ga 732Sends the 733.Dv TELNET GA 734(Go Ahead) 735sequence, which likely has no significance to the remote system. 736.It Ic getstatus 737If the remote side supports the 738.Dv TELNET STATUS 739command, 740.Ic getstatus 741will send the subnegotiation to request that the server send 742its current option status. 743.It Ic ip 744Sends the 745.Dv TELNET IP 746(Interrupt Process) sequence, which should cause the remote 747system to abort the currently running process. 748.It Ic nop 749Sends the 750.Dv TELNET NOP 751(No OPeration) 752sequence. 753.It Ic susp 754Sends the 755.Dv TELNET SUSP 756(SUSPend process) 757sequence. 758.It Ic synch 759Sends the 760.Dv TELNET SYNCH 761sequence. 762This sequence causes the remote system to discard all previously typed 763(but not yet read) input. 764This sequence is sent as 765.Tn TCP 766urgent 767data (and may not work if the remote system is a 768.Bx 4.2 769system -- if 770it doesn't work, a lower case \*(Lqr\*(Rq may be echoed on the terminal). 771.It Ic do Ar cmd 772.It Ic dont Ar cmd 773.It Ic will Ar cmd 774.It Ic wont Ar cmd 775Sends the 776.Dv TELNET DO 777.Ar cmd 778sequence. 779.Ar Cmd 780can be either a decimal number between 0 and 255, 781or a symbolic name for a specific 782.Dv TELNET 783command. 784.Ar Cmd 785can also be either 786.Ic help 787or 788.Ic ?\& 789to print out help information, including 790a list of known symbolic names. 791.It Ic ?\& 792Prints out help information for the 793.Ic send 794command. 795.El 796.It Ic set Ar argument value 797.It Ic unset Ar argument value 798The 799.Ic set 800command will set any one of a number of 801.Nm 802variables to a specific value or to 803.Dv TRUE . 804The special value 805.Ic off 806turns off the function associated with 807the variable, this is equivalent to using the 808.Ic unset 809command. 810The 811.Ic unset 812command will disable or set to 813.Dv FALSE 814any of the specified functions. 815The values of variables may be interrogated with the 816.Ic display 817command. 818The variables which may be set or unset, but not toggled, are 819listed here. 820In addition, any of the variables for the 821.Ic toggle 822command may be explicitly set or unset using 823the 824.Ic set 825and 826.Ic unset 827commands. 828.Bl -tag -width escape 829.It Ic ayt 830If 831.Tn TELNET 832is in localchars mode, or 833.Dv LINEMODE 834is enabled, and the status character is typed, a 835.Dv TELNET AYT 836sequence (see 837.Ic send ayt 838preceding) is sent to the 839remote host. 840The initial value for the \*(LqAre You There\*(Rq 841character is the terminal's status character. 842.It Ic echo 843This is the value (initially \*(Lq^E\*(Rq) which, when in 844\*(Lqline by line\*(Rq mode, toggles between doing local echoing 845of entered characters (for normal processing), and suppressing 846echoing of entered characters (for entering, say, a password). 847.It Ic eof 848If 849.Nm 850is operating in 851.Dv LINEMODE 852or \*(Lqold line by line\*(Rq mode, entering this character 853as the first character on a line will cause this character to be 854sent to the remote system. 855The initial value of the eof character is taken to be the terminal's 856.Ic eof 857character. 858.It Ic erase 859If 860.Nm 861is in 862.Ic localchars 863mode (see 864.Ic toggle 865.Ic localchars 866below), 867.Sy and 868if 869.Nm 870is operating in \*(Lqcharacter at a time\*(Rq mode, then when this 871character is typed, a 872.Dv TELNET EC 873sequence (see 874.Ic send 875.Ic ec 876above) 877is sent to the remote system. 878The initial value for the erase character is taken to be 879the terminal's 880.Ic erase 881character. 882.It Ic escape 883This is the 884.Nm 885escape character (initially \*(Lq^[\*(Rq) which causes entry 886into 887.Nm 888command mode (when connected to a remote system). 889.It Ic flushoutput 890If 891.Nm 892is in 893.Ic localchars 894mode (see 895.Ic toggle 896.Ic localchars 897below) 898and the 899.Ic flushoutput 900character is typed, a 901.Dv TELNET AO 902sequence (see 903.Ic send 904.Ic ao 905above) 906is sent to the remote host. 907The initial value for the flush character is taken to be 908the terminal's 909.Ic flush 910character. 911.It Ic forw1 912.It Ic forw2 913If 914.Nm 915is operating in 916.Dv LINEMODE , 917these are the 918characters that, when typed, cause partial lines to be 919forwarded to the remote system. 920The initial value for 921the forwarding characters are taken from the terminal's 922eol and eol2 characters. 923.It Ic interrupt 924If 925.Nm 926is in 927.Ic localchars 928mode (see 929.Ic toggle 930.Ic localchars 931below) 932and the 933.Ic interrupt 934character is typed, a 935.Dv TELNET IP 936sequence (see 937.Ic send 938.Ic ip 939above) 940is sent to the remote host. 941The initial value for the interrupt character is taken to be 942the terminal's 943.Ic intr 944character. 945.It Ic kill 946If 947.Nm 948is in 949.Ic localchars 950mode (see 951.Ic toggle 952.Ic localchars 953below), 954.Ic and 955if 956.Nm 957is operating in \*(Lqcharacter at a time\*(Rq mode, then when this 958character is typed, a 959.Dv TELNET EL 960sequence (see 961.Ic send 962.Ic el 963above) 964is sent to the remote system. 965The initial value for the kill character is taken to be 966the terminal's 967.Ic kill 968character. 969.It Ic lnext 970If 971.Nm 972is operating in 973.Dv LINEMODE 974or \*(Lqold line by line\*(Rq mode, then this character is taken to 975be the terminal's 976.Ic lnext 977character. 978The initial value for the lnext character is taken to be 979the terminal's 980.Ic lnext 981character. 982.It Ic quit 983If 984.Nm 985is in 986.Ic localchars 987mode (see 988.Ic toggle 989.Ic localchars 990below) 991and the 992.Ic quit 993character is typed, a 994.Dv TELNET BRK 995sequence (see 996.Ic send 997.Ic brk 998above) 999is sent to the remote host. 1000The initial value for the quit character is taken to be 1001the terminal's 1002.Ic quit 1003character. 1004.It Ic reprint 1005If 1006.Nm 1007is operating in 1008.Dv LINEMODE 1009or \*(Lqold line by line\*(Rq mode, then this character is taken to 1010be the terminal's 1011.Ic reprint 1012character. 1013The initial value for the reprint character is taken to be 1014the terminal's 1015.Ic reprint 1016character. 1017.It Ic rlogin 1018This is the rlogin escape character. 1019If set, the normal 1020.Nm 1021escape character is ignored unless it is 1022preceded by this character at the beginning of a line. 1023This character, at the beginning of a line followed by 1024a "." closes the connection; when followed by a ^Z it 1025suspends the 1026.Nm 1027command. 1028The initial state is to 1029disable the 1030.Nm rlogin 1031escape character. 1032.It Ic start 1033If the 1034.Dv TELNET TOGGLE-FLOW-CONTROL 1035option has been enabled, 1036then this character is taken to 1037be the terminal's 1038.Ic start 1039character. 1040The initial value for the start character is taken to be 1041the terminal's 1042.Ic start 1043character. 1044.It Ic stop 1045If the 1046.Dv TELNET TOGGLE-FLOW-CONTROL 1047option has been enabled, 1048then this character is taken to 1049be the terminal's 1050.Ic stop 1051character. 1052The initial value for the stop character is taken to be 1053the terminal's 1054.Ic stop 1055character. 1056.It Ic susp 1057If 1058.Nm 1059is in 1060.Ic localchars 1061mode, or 1062.Dv LINEMODE 1063is enabled, and the 1064.Ic suspend 1065character is typed, a 1066.Dv TELNET SUSP 1067sequence (see 1068.Ic send 1069.Ic susp 1070above) 1071is sent to the remote host. 1072The initial value for the suspend character is taken to be 1073the terminal's 1074.Ic suspend 1075character. 1076.It Ic tracefile 1077This is the file to which the output, caused by 1078.Ic netdata 1079or 1080.Ic option 1081tracing being 1082.Dv TRUE , 1083will be written. 1084If it is set to 1085.Dq Fl , 1086then tracing information will be written to standard output (the default). 1087.It Ic worderase 1088If 1089.Nm 1090is operating in 1091.Dv LINEMODE 1092or \*(Lqold line by line\*(Rq mode, then this character is taken to 1093be the terminal's 1094.Ic worderase 1095character. 1096The initial value for the worderase character is taken to be 1097the terminal's 1098.Ic worderase 1099character. 1100.It Ic ?\& 1101Displays the legal 1102.Ic set 1103.Pq Ic unset 1104commands. 1105.El 1106.It Ic opie Ar sequence challenge 1107The 1108.Ic opie 1109command computes a response to the OPIE challenge. 1110.It Ic slc Ar state 1111The 1112.Ic slc 1113command (Set Local Characters) is used to set 1114or change the state of the special 1115characters when the 1116.Dv TELNET LINEMODE 1117option has 1118been enabled. 1119Special characters are characters that get 1120mapped to 1121.Tn TELNET 1122commands sequences (like 1123.Ic ip 1124or 1125.Ic quit ) 1126or line editing characters (like 1127.Ic erase 1128and 1129.Ic kill ) . 1130By default, the local special characters are exported. 1131.Bl -tag -width Fl 1132.It Ic check 1133Verify the current settings for the current special characters. 1134The remote side is requested to send all the current special 1135character settings, and if there are any discrepancies with 1136the local side, the local side will switch to the remote value. 1137.It Ic export 1138Switch to the local defaults for the special characters. 1139The 1140local default characters are those of the local terminal at 1141the time when 1142.Nm 1143was started. 1144.It Ic import 1145Switch to the remote defaults for the special characters. 1146The remote default characters are those of the remote system 1147at the time when the 1148.Tn TELNET 1149connection was established. 1150.It Ic ?\& 1151Prints out help information for the 1152.Ic slc 1153command. 1154.El 1155.It Ic status 1156Show the current status of 1157.Nm . 1158This includes the peer one is connected to, as well 1159as the current mode. 1160.It Ic toggle Ar arguments ... 1161Toggle (between 1162.Dv TRUE 1163and 1164.Dv FALSE ) 1165various flags that control how 1166.Nm 1167responds to events. 1168These flags may be set explicitly to 1169.Dv TRUE 1170or 1171.Dv FALSE 1172using the 1173.Ic set 1174and 1175.Ic unset 1176commands listed above. 1177More than one argument may be specified. 1178The state of these flags may be interrogated with the 1179.Ic display 1180command. 1181Valid arguments are: 1182.Bl -tag -width Ar 1183.It Ic authdebug 1184Turns on debugging information for the authentication code. 1185.It Ic autoflush 1186If 1187.Ic autoflush 1188and 1189.Ic localchars 1190are both 1191.Dv TRUE , 1192then when the 1193.Ic ao , 1194or 1195.Ic quit 1196characters are recognized (and transformed into 1197.Tn TELNET 1198sequences; see 1199.Ic set 1200above for details), 1201.Nm 1202refuses to display any data on the user's terminal 1203until the remote system acknowledges (via a 1204.Dv TELNET TIMING MARK 1205option) 1206that it has processed those 1207.Tn TELNET 1208sequences. 1209The initial value for this toggle is 1210.Dv TRUE 1211if the terminal user had not 1212done an "stty noflsh", otherwise 1213.Dv FALSE 1214(see 1215.Xr stty 1 ) . 1216.It Ic autodecrypt 1217When the 1218.Dv TELNET ENCRYPT 1219option is negotiated, by 1220default the actual encryption (decryption) of the data 1221stream does not start automatically. 1222The autoencrypt 1223(autodecrypt) command states that encryption of the 1224output (input) stream should be enabled as soon as 1225possible. 1226.It Ic autologin 1227If the remote side supports the 1228.Dv TELNET AUTHENTICATION 1229option 1230.Nm 1231attempts to use it to perform automatic authentication. 1232If the 1233.Dv AUTHENTICATION 1234option is not supported, the user's login 1235name are propagated through the 1236.Dv TELNET ENVIRON 1237option. 1238This command is the same as specifying 1239.Fl a 1240option on the 1241.Ic open 1242command. 1243.It Ic autosynch 1244If 1245.Ic autosynch 1246and 1247.Ic localchars 1248are both 1249.Dv TRUE , 1250then when either the 1251.Ic intr 1252or 1253.Ic quit 1254characters is typed (see 1255.Ic set 1256above for descriptions of the 1257.Ic intr 1258and 1259.Ic quit 1260characters), the resulting 1261.Tn TELNET 1262sequence sent is followed by the 1263.Dv TELNET SYNCH 1264sequence. 1265This procedure 1266.Ic should 1267cause the remote system to begin throwing away all previously 1268typed input until both of the 1269.Tn TELNET 1270sequences have been read and acted upon. 1271The initial value of this toggle is 1272.Dv FALSE . 1273.It Ic binary 1274Enable or disable the 1275.Dv TELNET BINARY 1276option on both input and output. 1277.It Ic inbinary 1278Enable or disable the 1279.Dv TELNET BINARY 1280option on input. 1281.It Ic outbinary 1282Enable or disable the 1283.Dv TELNET BINARY 1284option on output. 1285.It Ic crlf 1286If this is 1287.Dv TRUE , 1288then carriage returns will be sent as 1289.Li <CR><LF> . 1290If this is 1291.Dv FALSE , 1292then carriage returns will be send as 1293.Li <CR><NUL> . 1294The initial value for this toggle is 1295.Dv FALSE . 1296.It Ic crmod 1297Toggle carriage return mode. 1298When this mode is enabled, most carriage return characters received from 1299the remote host will be mapped into a carriage return followed by 1300a line feed. 1301This mode does not affect those characters typed by the user, only 1302those received from the remote host. 1303This mode is not very useful unless the remote host 1304only sends carriage return, but never line feed. 1305The initial value for this toggle is 1306.Dv FALSE . 1307.It Ic debug 1308Toggles socket level debugging (useful only to the 1309.Ic super user ) . 1310The initial value for this toggle is 1311.Dv FALSE . 1312.It Ic encdebug 1313Turns on debugging information for the encryption code. 1314.It Ic localchars 1315If this is 1316.Dv TRUE , 1317then the 1318.Ic flush , 1319.Ic interrupt , 1320.Ic quit , 1321.Ic erase , 1322and 1323.Ic kill 1324characters (see 1325.Ic set 1326above) are recognized locally, and transformed into (hopefully) appropriate 1327.Tn TELNET 1328control sequences 1329(respectively 1330.Ic ao , 1331.Ic ip , 1332.Ic brk , 1333.Ic ec , 1334and 1335.Ic el ; 1336see 1337.Ic send 1338above). 1339The initial value for this toggle is 1340.Dv TRUE 1341in \*(Lqold line by line\*(Rq mode, 1342and 1343.Dv FALSE 1344in \*(Lqcharacter at a time\*(Rq mode. 1345When the 1346.Dv LINEMODE 1347option is enabled, the value of 1348.Ic localchars 1349is ignored, and assumed to always be 1350.Dv TRUE . 1351If 1352.Dv LINEMODE 1353has ever been enabled, then 1354.Ic quit 1355is sent as 1356.Ic abort , 1357and 1358.Ic eof 1359and 1360.Ic suspend 1361are sent as 1362.Ic eof 1363and 1364.Ic susp 1365(see 1366.Ic send 1367above). 1368.It Ic netdata 1369Toggles the display of all network data (in hexadecimal format). 1370The initial value for this toggle is 1371.Dv FALSE . 1372.It Ic options 1373Toggles the display of some internal 1374.Nm 1375protocol processing (having to do with 1376.Tn TELNET 1377options). 1378The initial value for this toggle is 1379.Dv FALSE . 1380.It Ic prettydump 1381When the 1382.Ic netdata 1383toggle is enabled, if 1384.Ic prettydump 1385is enabled the output from the 1386.Ic netdata 1387command will be formatted in a more user readable format. 1388Spaces are put between each character in the output, and the 1389beginning of any 1390.Nm 1391escape sequence is preceded by a '*' to aid in locating them. 1392.It Ic skiprc 1393When the skiprc toggle is 1394.Dv TRUE , 1395.Nm 1396skips the reading of the 1397.Pa \&.telnetrc 1398file in the users home 1399directory when connections are opened. 1400The initial 1401value for this toggle is 1402.Dv FALSE . 1403.It Ic termdata 1404Toggles the display of all terminal data (in hexadecimal format). 1405The initial value for this toggle is 1406.Dv FALSE . 1407.It Ic verbose_encrypt 1408When the 1409.Ic verbose_encrypt 1410toggle is 1411.Dv TRUE , 1412.Nm 1413prints out a message each time encryption is enabled or 1414disabled. 1415The initial value for this toggle is 1416.Dv FALSE . 1417.It Ic ?\& 1418Displays the legal 1419.Ic toggle 1420commands. 1421.El 1422.It Ic z 1423Suspend 1424.Nm . 1425This command only works when the user is using the 1426.Xr csh 1 . 1427.It Ic \&! Op Ar command 1428Execute a single command in a subshell on the local 1429system. 1430If 1431.Ar command 1432is omitted, then an interactive 1433subshell is invoked. 1434.It Ic ?\& Op Ar command 1435Get help. 1436With no arguments, 1437.Nm 1438prints a help summary. 1439If 1440.Ar command 1441is specified, 1442.Nm 1443will print the help information for just that command. 1444.El 1445.Sh ENVIRONMENT 1446.Nm 1447uses at least the 1448.Ev HOME , 1449.Ev SHELL , 1450.Ev DISPLAY , 1451and 1452.Ev TERM 1453environment variables. 1454Other environment variables may be propagated 1455to the other side via the 1456.Dv TELNET ENVIRON 1457option. 1458.Sh FILES 1459.Bl -tag -width ~/.telnetrc -compact 1460.It Pa ~/.telnetrc 1461user customized telnet startup values 1462.El 1463.Sh SEE ALSO 1464.Xr rlogin 1 , 1465.Xr rsh 1 , 1466.Xr hosts 5 , 1467.Xr nologin 5 , 1468.Xr telnetd 8 1469.Sh HISTORY 1470The 1471.Nm 1472command appeared in 1473.Bx 4.2 . 1474.Pp 1475IPv6 support was added by WIDE/KAME project. 1476.Sh NOTES 1477On some remote systems, echo has to be turned off manually when in 1478\*(Lqold line by line\*(Rq mode. 1479.Pp 1480In \*(Lqold line by line\*(Rq mode or 1481.Dv LINEMODE 1482the terminal's 1483.Ic eof 1484character is only recognized (and sent to the remote system) 1485when it is the first character on a line. 1486