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diff --git a/man/man5/services.5 b/man/man5/services.5 new file mode 100644 index 0000000..0d8f6c8 --- /dev/null +++ b/man/man5/services.5 @@ -0,0 +1,199 @@ +.\" This manpage is Copyright (C) 1996 Austin Donnelly <and1000@cam.ac.uk>, +.\" with additional material Copyright (c) 1995 Martin Schulze +.\" <joey@infodrom.north.de> +.\" +.\" SPDX-License-Identifier: Linux-man-pages-copyleft +.\" +.\" This manpage was made by merging two independently written manpages, +.\" one written by Martin Schulze (18 Oct 95), the other written by +.\" Austin Donnelly, (9 Jan 96). +.\" +.\" Thu Jan 11 12:14:41 1996 Austin Donnelly <and1000@cam.ac.uk> +.\" * Merged two services(5) manpages +.\" +.TH services 5 2024-05-02 "Linux man-pages (unreleased)" +.SH NAME +services \- Internet network services list +.SH DESCRIPTION +.B services +is a plain ASCII file providing a mapping between human-friendly textual +names for internet services, and their underlying assigned port +numbers and protocol types. +Every networking program should look into +this file to get the port number (and protocol) for its service. +The C library routines +.BR getservent (3), +.BR getservbyname (3), +.BR getservbyport (3), +.BR setservent (3), +and +.BR endservent (3) +support querying this file from programs. +.P +Port numbers are assigned by the IANA (Internet Assigned Numbers +Authority), and their current policy is to assign both TCP and UDP +protocols when assigning a port number. +Therefore, most entries will +have two entries, even for TCP-only services. +.P +Port numbers below 1024 (so-called "low numbered" ports) can be +bound to only by root (see +.BR bind (2), +.BR tcp (7), +and +.BR udp (7)). +This is so clients connecting to low numbered ports can trust +that the service running on the port is the standard implementation, +and not a rogue service run by a user of the machine. +Well-known port numbers specified by the IANA are normally +located in this root-only space. +.P +The presence of an entry for a service in the +.B services +file does not necessarily mean that the service is currently running +on the machine. +See +.BR inetd.conf (5) +for the configuration of Internet services offered. +Note that not all +networking services are started by +.BR inetd (8), +and so won't appear in +.BR inetd.conf (5). +In particular, news (NNTP) and mail (SMTP) servers are often +initialized from the system boot scripts. +.P +The location of the +.B services +file is defined by +.B _PATH_SERVICES +in +.IR <netdb.h> "." +This is usually set to +.IR /etc/services "." +.P +Each line describes one service, and is of the form: +.IP +\f2service-name\ \ \ port\f3/\f2protocol\ \ \ \f1[\f2aliases ...\f1] +.TP +where: +.TP +.I service-name +is the friendly name the service is known by and looked up under. +It is case sensitive. +Often, the client program is named after the +.IR service-name "." +.TP +.I port +is the port number (in decimal) to use for this service. +.TP +.I protocol +is the type of protocol to be used. +This field should match an entry +in the +.BR protocols (5) +file. +Typical values include +.B tcp +and +.BR udp . +.TP +.I aliases +is an optional space or tab separated list of other names for this +service. +Again, the names are case +sensitive. +.P +Either spaces or tabs may be used to separate the fields. +.P +Comments are started by the hash sign (#) and continue until the end +of the line. +Blank lines are skipped. +.P +The +.I service-name +should begin in the first column of the file, since leading spaces are +not stripped. +.I service-names +can be any printable characters excluding space and tab. +However, a conservative choice of characters should be used to minimize +compatibility problems. +For example, a\-z, 0\-9, and hyphen (\-) would seem a +sensible choice. +.P +Lines not matching this format should not be present in the +file. +(Currently, they are silently skipped by +.BR getservent (3), +.BR getservbyname (3), +and +.BR getservbyport (3). +However, this behavior should not be relied on.) +.P +.\" The following is not true as at glibc 2.8 (a line with a comma is +.\" ignored by getservent()); it's not clear if/when it was ever true. +.\" As a backward compatibility feature, the slash (/) between the +.\" .I port +.\" number and +.\" .I protocol +.\" name can in fact be either a slash or a comma (,). +.\" Use of the comma in +.\" modern installations is deprecated. +.\" +This file might be distributed over a network using a network-wide +naming service like Yellow Pages/NIS or BIND/Hesiod. +.P +A sample +.B services +file might look like this: +.P +.in +4n +.EX +netstat 15/tcp +qotd 17/tcp quote +msp 18/tcp # message send protocol +msp 18/udp # message send protocol +chargen 19/tcp ttytst source +chargen 19/udp ttytst source +ftp 21/tcp +# 22 \- unassigned +telnet 23/tcp +.EE +.in +.SH FILES +.TP +.I /etc/services +The Internet network services list +.TP +.I <netdb.h> +Definition of +.B _PATH_SERVICES +.\" .SH BUGS +.\" It's not clear when/if the following was ever true; +.\" it isn't true for glibc 2.8: +.\" There is a maximum of 35 aliases, due to the way the +.\" .BR getservent (3) +.\" code is written. +.\" +.\" It's not clear when/if the following was ever true; +.\" it isn't true for glibc 2.8: +.\" Lines longer than +.\" .B BUFSIZ +.\" (currently 1024) characters will be ignored by +.\" .BR getservent (3), +.\" .BR getservbyname (3), +.\" and +.\" .BR getservbyport (3). +.\" However, this will also cause the next line to be mis-parsed. +.SH SEE ALSO +.BR listen (2), +.BR endservent (3), +.BR getservbyname (3), +.BR getservbyport (3), +.BR getservent (3), +.BR setservent (3), +.BR inetd.conf (5), +.BR protocols (5), +.BR inetd (8) +.P +Assigned Numbers RFC, most recently RFC\ 1700, (AKA STD0002). |