fd: integer file descriptor on POSIX systems, NA on Windows.
family: Address family, string, typically AF_UNIX, AF_INET or
AF_INET6.
type: Socket type, string, typically SOCK_STREAM (TCP) or
SOCK_DGRAM (UDP).
laddr: Local address, string, NA for UNIX sockets.
lport: Local port, integer, NA for UNIX sockets.
raddr: Remote address, string, NA for UNIX sockets. This is
always NA for AF_INET sockets on Linux.
rport: Remote port, integer, NA for UNIX sockets.
state: Socket state, e.g. CONN_ESTABLISHED, etc. It is NA
for UNIX sockets.