# do some "forward" DNS lookups.  "man dig"

dig www.google.com
dig @ns1.google.com www.google.com
dig any @ns1.google.com google.com
dig any @june.cs.washington.edu cs.washington.edu

# lookup well-known alias for local machine
dig localhost.localdomain

# do a reverse DNS lookup
dig -x 128.95.4.1

# run a trace of the DNS lookup path, disabling recursion as a side-effect
dig +trace www.cs.washington.edu

# run netcat to open a listening socket on port 5543
nc -l 5543

                 # in a second window talk to it
                 nc 127.0.0.1 5543
                 anything typed in either window
                 is displayed on both
                 use ^D to shut down

# sendreceive demo
# window 1                    # window 2
g++ -Wall sendreceive.cc
                              nc -l 3456
./a.out 127.0.0.1 3456
                              type a message here, see it there