what does this ip address notation means [::]:[4443].

  • 2
    [::]:[4443] looks like a typo. It should have said [::]:4443 – kasperd Dec 27 '17 at 22:25

[::] indicate all ipv6 addresses. 4443 is a port number. So if a service is bound to [::]:4443 it'll be listening to all ipv6 addresses available in your system. It's similar to listening for ipv4.

Some services bind to all IPs available (including ipv4) while binding to [::]. Strictly speaking [::] indicates ipv6 only. As per ipv6 writing convention, one consecutive block of 0's in an ipv6 address can be replaced with ::. Considering ipv6 is 128 bits the address :: is 0000:0000:0000:0000:0000:0000:0000:0000 in expanded hexadecimal form.

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  • 3
    s/one contentious block/a contiguous group/ or /a consecutive group/. v4 addresses are mapped into v6 (at ::ffff:0000:0000/96) so listening on :: can accept both v6 and v4 if the implementation chooses, usually called 'single-stack'; only 'dual-stack' implementations require separate listens on :: and – dave_thompson_085 Dec 27 '17 at 12:17
  • so what you are saying is that 4443 is listening port for all ipv4 and ipv6 addresses. – captainchhala Dec 28 '17 at 5:01

It's a bind designation to port 4443 of all interfaces that support IPv6. It is equivalent to [0000:0000:0000:0000:0000:0000:0000:0000]:4443.

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