In addition to the responses from others, I just wanted to point out that the string "::1" is an IPv6 equivilant to "127.0.0.1" in IPv4, both of which are normally associated with the "localhost" hostname.
IPv6 has been in production for many years now, and due to the shortage of available IPv4 addresses it is becoming increasingly prevalent throughout the world. For a real world implementation, one good example can be seen in PostgreSQL's documentation: https://www.postgresql.org/docs/10/static/datatype-net-types.html Perl itself and mod_perl2 both support IPv4 and IPv6 without any difficulties in the projects that I work on, so with that in mind... If you have any code that arbitrarily supports only IPv4 addresses, then you should seriously consider making it a higher priority to add support for IPv6. For example, if you rely on Regular Expressions to validate IPv4 addresses specifically, then be aware that any valid IPv6 addresses will not register as matches due to the inclusion of additional characters that are not used to represent IPv4 addresses. > I saw many items like these in log, > > ::1 - - [05/Jun/2017:14:29:06 +0800] "OPTIONS * HTTP/1.0" 200 125 "-" > "Apache/2.4.7 (Ubuntu) PHP/5.5.9-1ubuntu4.21 mod_apreq2-20090110/2.8.0 > mod_perl/2.0.8 Perl/v5.18.2 (internal dummy connection)" > ::1 - - [05/Jun/2017:14:29:07 +0800] "OPTIONS * HTTP/1.0" 200 125 "-" > "Apache/2.4.7 (Ubuntu) PHP/5.5.9-1ubuntu4.21 mod_apreq2-20090110/2.8.0 > mod_perl/2.0.8 Perl/v5.18.2 (internal dummy connection)" > ::1 - - [05/Jun/2017:14:29:08 +0800] "OPTIONS * HTTP/1.0" 200 125 "-" > "Apache/2.4.7 (Ubuntu) PHP/5.5.9-1ubuntu4.21 mod_apreq2-20090110/2.8.0 > mod_perl/2.0.8 Perl/v5.18.2 (internal dummy connection)" > ::1 - - [05/Jun/2017:14:29:09 +0800] "OPTIONS * HTTP/1.0" 200 125 "-" > "Apache/2.4.7 (Ubuntu) PHP/5.5.9-1ubuntu4.21 mod_apreq2-20090110/2.8.0 > mod_perl/2.0.8 Perl/v5.18.2 (internal dummy connection)" > > what does it mean? why it exists? thanks. Randolf Richardson - rand...@inter-corporate.com Inter-Corporate Computer & Network Services, Inc. Beautiful British Columbia, Canada http://www.inter-corporate.com/