Linux系统可以通过手工编辑配置文件达到对系统进行配置的目的，例如将/etc/inted.conf文件中“#FTP　Stream　TCP　nowait　root/usr/sbin/tcpd　in.ftpd　-1　-a”前的“#”去掉就可以开启FTP服务。修改(39)文件可对允许访问FTP服务的主机范围进行限制。

(94)

(93)

(92)

(91)

The　major　problem　with　E-mail　is　that　it　is(71)easy　to　use　that　people　can　become(72)with　messages(73)they　can　possibly　answer　in　a　day.　In　addition,　mail　boxes　require　some　management　to(74)messages　or　archive　those　that　might　be　required　later.　Senders　don't　always　know　about　your　E-mail　backlog　and　often　send(75)messages.

(89)

(87)

(88)

Communication　protocols　are(66)connection-oriented　or　connectionless,(67)whether　the　sender　of　a　message　needs　to　contact　and　maintain　a　dialog　with　the　recipient　or(68)send　a　message　without　any,　prior　connect　and　with　the　hope　that　the　recipient　receives　everything.(69).These　methods(70)the　two　ways　that　communication　is　implemented　on　networks.

(86)