4.3BSD-UWisc/man/cat8/telnetd.8c

TELNETD(8C)         UNIX Programmer's Manual          TELNETD(8C)



NAME
     telnetd - DARPA TELNET protocol server

SYNOPSIS
     /etc/telnetd

DESCRIPTION
     _T_e_l_n_e_t_d is a server which supports the DARPA standard TELNET
     virtual terminal protocol.  _T_e_l_n_e_t_d is invoked by the inter-
     net server (see _i_n_e_t_d(8)), normally for requests to connect
     to the TELNET 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)).

     _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 stdin, stdout,
     and stderr.  _T_e_l_n_e_t_d manipulates the master side of the
     pseudo-terminal, implementing the TELNET protocol and pass-
     ing characters between the remote client and the login pro-
     cess.

     When a TELNET session is started up, _t_e_l_n_e_t_d sends TELNET
     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, 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 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: _b_i_n_a_r_y, _t_e_r_m_i_n_a_l _t_y_p_e, and _s_u_p_p_r_e_s_s _g_o _a_h_e_a_d.

SEE ALSO
     telnet(1C)

BUGS
     Some TELNET commands are only partially implemented.

     The TELNET protocol allows for the exchange of the number of
     lines and columns on the user's terminal, but _t_e_l_n_e_t_d
     doesn't make use of them.

     Because of bugs in the original 4.2 BSD _t_e_l_n_e_t(1C), _t_e_l_n_e_t_d
     performs some dubious protocol exchanges to try to discover
     if the remote client is, in fact, a 4.2 BSD _t_e_l_n_e_t(1C).

     _B_i_n_a_r_y _m_o_d_e has no common interpretation except between
     similar operating systems (Unix in this case).




Printed 12/27/86          May 28, 1986                          1






TELNETD(8C)         UNIX Programmer's Manual          TELNETD(8C)



     The terminal type name received from the remote client is
     converted to lower case.

     The _p_a_c_k_e_t interface to the pseudo-terminal (see _p_t_y(4))
     should be used for more intelligent flushing of input and
     output queues.

     _T_e_l_n_e_t_d never sends TELNET _g_o _a_h_e_a_d commands.















































Printed 12/27/86          May 28, 1986                          2