LINUX ONLY
Shows both ipv4 and ipv6 addresses.
    ip addr[ess] show

Shows only ipv6 addresses
    ip -6 addr[ess] show

HSQLDB Server failure
java.net.BindException: Cannot assign requested address
        at java.net.PlainSocketImpl.socketBind(Native Method)
        at java.net.PlainSocketImpl.bind(PlainSocketImpl.java:359)
        at java.net.ServerSocket.bind(ServerSocket.java:319)
        at java.net.ServerSocket.<init>(ServerSocket.java:185)
        at org.hsqldb.HsqlSocketFactory.createServerSocket(HsqlSocketFactory.java:109)
        at org.hsqldb.Server.openServerSocket(Server.java:1951)
        at org.hsqldb.Server.run(Server.java:2078)
        at org.hsqldb.Server.access$000(Server.java:214)
        at org.hsqldb.Server$ServerThread.run(Server.java:278)

HSQLDB Client failure
Failed to get a connection to jdbc:hsqldb:hsql://[::1]:9111 as sa.  SOO10 Invalid argument in JDBC call

Notation  (frm Wikipedia
--------
Addr is 128 bits or 16 bytes
8 groups of 4 hex digits separated by :s (2 bytes/group).
Leading zeros in any group may be omitted
ONCE in each addr,
 any number of consecutive groups of 0 may be replaced with ::.
Default /bit-block-size is 128.
May enclose ipv6 addr in square brackets WHEN PORT also given and in URLs
REQUIRED if any :: shortcuts.
    http://[2001:0db8:85a3:08d3:1319:8a2e:0370:7348]/.
    https://[2001:db8::1428:57ab]:443/

Special addresses:
    ::1 = localhost
    :: = Unspecified (all-bits-empty = 0)
    2001:db8::/32  For documentation examples
    fe80://10      Link-local address is generated automatically for each iface.
                   (says same as 169.254.0.0/16 in ipv4?)

Address types
    Unicast:  normal
    Anycase addresses are indistinguishable to Unicast, but are used by
     multiple nodes, with only one node receiving each packet.
    Multicast.  What you would think.  FF00::/8
     The 4th nibble specifies scope of the multicasting.