Use Unix domain sockets rather than network sockets.
This option may be used on its own for stream sockets, or
combined with --udp for datagram sockets.
A description of -U mode is in
the section called “Unix Domain Sockets”.
--udp (Use UDP)
Use UDP for the connection (the default is TCP).
--sctp (Use SCTP)
Use SCTP for the connection (the default is TCP).
SCTP support is implemented in TCP-compatible mode.