4.4BSD/usr/share/man/cat8/telnetd.0
TELNETD(8) BSD System Manager's Manual TELNETD(8)
NNAAMMEE
telnetd - DARPA TELNET protocol server
SSYYNNOOPPSSIISS
//eettcc//tteellnneettdd [--ddeebbuugg [_p_o_r_t]] [--ll]] [[--DD ooppttiioonnss]] [[--DD rreeppoorrtt]]
[[--DD eexxeerrcciissee]] [[--DD nneettddaattaa]] [[--DD ppttyyddaattaa]]
DDEESSCCRRIIPPTTIIOONN
_T_e_l_n_e_t_d is a server which supports the DARPA standard TTEELL--
NNEETT virtual terminal protocol. _T_e_l_n_e_t_d is invoked by the
internet server (see _i_n_e_t_d(8)), normally for requests to
connect to the TTEELLNNEETT port as indicated by the
_/_e_t_c_/_s_e_r_v_i_c_e_s file (see _s_e_r_v_i_c_e_s(5)). If the --ddeebbuugg may
be used, to start up tteellnneettdd manually, instead of through
_i_n_e_t_d(8). If started up this way, _p_o_r_t may be specified
to run _t_e_l_n_e_t_d on an alternate TCP port number.
The --DD option may be used for debugging purposes. This
allows _t_e_l_n_e_t to print out debugging information to the
connection, allowing the user to see what telnetd is
doing. There are several modifiers: ooppttiioonnss prints infor-
mation about the negotiation of TTEELLNNEETT options, rreeppoorrtt
prints the ooppttiioonnss information, plus some additional
information about what processing is going on, nneettddaattaa
displays the data stream received by _t_e_l_n_e_t_d, ppttyyddaattaa dis-
plays data written to the pty, and eexxeerrcciissee has not been
implemented yet.
_T_e_l_n_e_t_d operates by allocating a pseudo-terminal device
(see _p_t_y(4)) for a client, then creating a login process
which has the slave side of the pseudo-terminal as ssttddiinn,
ssttddoouutt, and ssttddeerrrr. _T_e_l_n_e_t_d manipulates the master side
of the pseudo-terminal, implementing the TTEELLNNEETT protocol
and passing characters between the remote client and the
login process.
When a TTEELLNNEETT session is started up, _t_e_l_n_e_t_d sends TTEELLNNEETT
options to the client side indicating a willingness to do
_r_e_m_o_t_e _e_c_h_o of characters, to _s_u_p_p_r_e_s_s _g_o _a_h_e_a_d, to do
_r_e_m_o_t_e _f_l_o_w _c_o_n_t_r_o_l, and to receive _t_e_r_m_i_n_a_l _t_y_p_e _i_n_f_o_r_m_a_-
_t_i_o_n, _t_e_r_m_i_n_a_l _s_p_e_e_d _i_n_f_o_r_m_a_t_i_o_n, and _w_i_n_d_o_w _s_i_z_e _i_n_f_o_r_m_a_-
_t_i_o_n from the remote client. If the remote client is
willing, the remote terminal type is propagated in the
environment of the created login process. The pseudo-
terminal allocated to the client is configured to operate
in "cooked" mode, and with XTABS and CRMOD enabled (see
_t_t_y(4)).
_T_e_l_n_e_t_d is willing to _d_o: _e_c_h_o, _b_i_n_a_r_y, _s_u_p_p_r_e_s_s _g_o _a_h_e_a_d,
and _t_i_m_i_n_g _m_a_r_k. _T_e_l_n_e_t_d is willing to have the remote
client _d_o: _l_i_n_e_m_o_d_e, _b_i_n_a_r_y, _t_e_r_m_i_n_a_l _t_y_p_e, _t_e_r_m_i_n_a_l
4.2 Berkeley Distribution June 4, 1993 1
TELNETD(8) BSD System Manager's Manual TELNETD(8)
_s_p_e_e_d, _w_i_n_d_o_w _s_i_z_e, _t_o_g_g_l_e _f_l_o_w _c_o_n_t_r_o_l, _e_n_v_i_r_o_n_m_e_n_t, _X
_d_i_s_p_l_a_y _l_o_c_a_t_i_o_n, and _s_u_p_p_r_e_s_s _g_o _a_h_e_a_d.
SSEEEE AALLSSOO
telnet(1)
BBUUGGSS
Some TTEELLNNEETT commands are only partially implemented.
Because of bugs in the original 4.2 BSD _t_e_l_n_e_t(1), _t_e_l_n_e_t_d
performs some dubious protocol exchanges to try to dis-
cover if the remote client is, in fact, a 4.2 BSD _t_e_l_-
_n_e_t(1).
_B_i_n_a_r_y _m_o_d_e has no common interpretation except between
similar operating systems (Unix in this case).
The terminal type name received from the remote client is
converted to lower case.
_T_e_l_n_e_t_d never sends TTEELLNNEETT _g_o _a_h_e_a_d commands.
4.2 Berkeley Distribution June 4, 1993 2