service name database
services file contains information
regarding the known services available in the Internet. For each service, a
single line should be present with the following information:
official service name port number protocol name aliases
Items are separated by any number of blanks and/or tab characters.
The port number and protocol name are considered a single item; a slash
/’) is used to separate the port and
protocol (e.g., “512/tcp”).
A hash mark (‘
the beginning of a comment; subsequent characters up to the end of the line
are not interpreted by the routines which search the file.
Service names may contain any printable character other than a field delimiter, newline, or comment character.
To protect service ports from being used for dynamic port
assignment, rc(8) reads
services at boot and uses the
contents to populate net.inet.tcp.baddynamic and
While it is the policy of IANA to assign a single well-known port
number for both TCP and UDP, to avoid reducing the dynamic port range
unnecessarily, the unused entries are not always listed in
services file format appeared in
A name server should be used instead of a static file. Lines in
/etc/services are limited to
BUFSIZ characters (currently 1024). Longer lines
will be ignored.