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1 | .\" Hey Emacs! This file is -*- nroff -*- source. |
2 | .\" | |
3 | .\" This manpage is Copyright (C) 1996 Austin Donnelly <and1000@cam.ac.uk>, | |
4 | .\" with additional material (c) 1995 Martin Schulze <joey@infodrom.north.de> | |
5 | .\" | |
6 | .\" Permission is granted to make and distribute verbatim copies of this | |
7 | .\" manual provided the copyright notice and this permission notice are | |
8 | .\" preserved on all copies. | |
9 | .\" | |
10 | .\" Permission is granted to copy and distribute modified versions of this | |
11 | .\" manual under the conditions for verbatim copying, provided that the | |
12 | .\" entire resulting derived work is distributed under the terms of a | |
13 | .\" permission notice identical to this one. | |
14 | .\" | |
15 | .\" Since the Linux kernel and libraries are constantly changing, this | |
16 | .\" manual page may be incorrect or out-of-date. The author(s) assume no | |
17 | .\" responsibility for errors or omissions, or for damages resulting from | |
18 | .\" the use of the information contained herein. The author(s) may not | |
19 | .\" have taken the same level of care in the production of this manual, | |
20 | .\" which is licensed free of charge, as they might when working | |
21 | .\" professionally. | |
22 | .\" | |
23 | .\" Formatted or processed versions of this manual, if unaccompanied by | |
24 | .\" the source, must acknowledge the copyright and authors of this work. | |
25 | .\" | |
26 | .\" This manpage was made by merging two independently written manpages, | |
27 | .\" one written by Martin Schulze (18 Oct 95), the other written by | |
28 | .\" Austin Donnelly, (9 Jan 96). | |
29 | .\" | |
30 | .\" Thu Jan 11 12:14:41 1996 Austin Donnelly <and1000@cam.ac.uk> | |
31 | .\" * Merged two services(5) manpages | |
32 | .\" | |
33 | .TH SERVICES 5 1996-01-11 "Linux" "Linux Programmer's Manual" | |
34 | .SH NAME | |
35 | services \- Internet network services list | |
36 | .SH DESCRIPTION | |
37 | .B services | |
38 | is a plain ASCII file providing a mapping between friendly textual | |
39 | names for internet services, and their underlying assigned port | |
40 | numbers and protocol types. Every networking program should look into | |
41 | this file to get the port number (and protocol) for its service. | |
42 | The C library routines | |
43 | .BR getservent (3), | |
44 | .BR getservbyname (3), | |
45 | .BR getservbyport (3), | |
46 | .BR setservent (3), | |
47 | and | |
48 | .BR endservent (3) | |
49 | support querying this file from programs. | |
50 | ||
51 | Port numbers are assigned by the IANA (Internet Assigned Numbers | |
52 | Authority), and their current policy is to assign both TCP and UDP | |
53 | protocols when assigning a port number. Therefore, most entries will | |
54 | have two entries, even for TCP only services. | |
55 | ||
56 | Port numbers below 1024 (so-called 'low numbered' ports) can only be | |
57 | bound to by root (see | |
58 | .BR bind (2), | |
59 | .BR tcp (7), | |
60 | and | |
61 | .BR udp (7)). | |
62 | This is so clients connecting to low numbered ports can trust | |
63 | that the service running on the port is the standard implementation, | |
64 | and not a rogue service run by a user of the machine. Well-known port | |
65 | numbers specified by the IANA are normally located in this root-only | |
66 | space. | |
67 | ||
68 | The presence of an entry for a service in the | |
69 | .B services | |
70 | file does not necessarily mean that the service is currently running | |
71 | on the machine. See | |
72 | .BR inetd.conf (5) | |
73 | for the configuration of Internet services offered. Note that not all | |
74 | networking services are started by | |
75 | .BR inetd (8), | |
76 | and so won't appear in | |
77 | .BR inetd.conf (5). | |
78 | In particular, news (NNTP) and mail (SMTP) servers are often | |
79 | initialized from the system boot scripts. | |
80 | ||
81 | The location of the | |
82 | .B services | |
83 | file is defined by | |
84 | .B _PATH_SERVICES | |
85 | in | |
86 | .IR /usr/include/netdb.h "." | |
87 | This is usually set to | |
88 | .IR /etc/services "." | |
89 | ||
90 | Each line describes one service, and is of the form: | |
91 | .IP | |
92 | \f2service-name\ \ \ port\f3/\f2protocol\ \ \ \f1[\f2aliases ...\f1] | |
93 | .TP | |
94 | where: | |
95 | .TP 10 | |
96 | .I service-name | |
97 | is the friendly name the service is known by and looked up under. It | |
98 | is case sensitive. Often, the client program is named after the | |
99 | .IR service-name "." | |
100 | .TP | |
101 | .I port | |
102 | is the port number (in decimal) to use for this service. | |
103 | .TP | |
104 | .I protocol | |
105 | is the type of protocol to be used. This field should match an entry | |
106 | in the | |
107 | .BR protocols (5) | |
108 | file. Typical values include | |
109 | .B tcp | |
110 | and | |
111 | .BR udp . | |
112 | .TP | |
113 | .I aliases | |
114 | is an optional space or tab separated list of other names for this | |
115 | service (but see the BUGS section below). Again, the names are case | |
116 | sensitive. | |
117 | .PP | |
118 | ||
119 | Either spaces or tabs may be used to separate the fields. | |
120 | ||
121 | Comments are started by the hash sign (#) and continue until the end | |
122 | of the line. Blank lines are skipped. | |
123 | ||
124 | The | |
125 | .I service-name | |
126 | should begin in the first column of the file, since leading spaces are | |
127 | not stripped. | |
128 | .I service-names | |
129 | can be any printable characters excluding space and tab. However, | |
130 | a conservative choice of characters should be used to minimize | |
131 | inter-operability problems. E.g., a-z, 0-9, and hyphen (\-) would seem a | |
132 | sensible choice. | |
133 | ||
134 | Lines not matching this format should not be present in the | |
135 | file. (Currently, they are silently skipped by | |
136 | .BR getservent (3), | |
137 | .BR getservbyname (3), | |
138 | and | |
139 | .BR getservbyport (3). | |
140 | However, this behaviour should not be relied on.) | |
141 | ||
142 | As a backwards compatibility feature, the slash (/) between the | |
143 | .I port | |
144 | number and | |
145 | .I protocol | |
146 | name can in fact be either a slash or a comma (,). Use of the comma in | |
147 | modern installations is depreciated. | |
148 | ||
149 | This file might be distributed over a network using a network-wide | |
150 | naming service like Yellow Pages/NIS or BIND/Hesiod. | |
151 | ||
152 | A sample | |
153 | .B services | |
154 | file might look like this: | |
155 | .RS | |
156 | .nf | |
157 | .sp | |
158 | .ta 3i | |
159 | netstat 15/tcp | |
160 | qotd 17/tcp quote | |
161 | msp 18/tcp # message send protocol | |
162 | msp 18/udp # message send protocol | |
163 | chargen 19/tcp ttytst source | |
164 | chargen 19/udp ttytst source | |
165 | ftp 21/tcp | |
2bc2f479 | 166 | # 22 \- unassigned |
fea681da MK |
167 | telnet 23/tcp |
168 | .sp | |
169 | .fi | |
170 | .RE | |
171 | .SH BUGS | |
172 | There is a maximum of 35 aliases, due to the way the | |
173 | .BR getservent (3) | |
174 | code is written. | |
175 | ||
176 | Lines longer than | |
177 | .B BUFSIZ | |
178 | (currently 1024) characters will be ignored by | |
179 | .BR getservent (3), | |
180 | .BR getservbyname (3), | |
181 | and | |
182 | .BR getservbyport (3). | |
183 | However, this will also cause the next line to be mis-parsed. | |
184 | .SH FILES | |
185 | .TP | |
186 | .I /etc/services | |
187 | The Internet network services list | |
188 | .TP | |
189 | .I /usr/include/netdb.h | |
190 | Definition of | |
191 | .B _PATH_SERVICES | |
192 | .SH "SEE ALSO" | |
193 | .BR listen (2), | |
194 | .BR endservent (3), | |
195 | .BR getservbyname (3), | |
196 | .BR getservbyport (3), | |
197 | .BR getservent (3), | |
198 | .BR setservent (3), | |
199 | .BR inetd.conf (5), | |
200 | .BR protocols (5), | |
201 | .BR inetd (8) | |
202 | ||
203 | Assigned Numbers RFC, most recently RFC 1700, (AKA STD0002) | |
204 | ||
205 | Guide to Yellow Pages Service | |
206 | ||
207 | Guide to BIND/Hesiod Service |