Generic commands that use /etc/mailcap: see, edit, print, compose

socat is the swiss army knife that just about lets you forget everything's not a file:

$ socat readline: file:/dev/ttyS0,crnl,crtscts,echo=0 # interact with a serial port

$ socat readline: tcp:google.com:80 # interact with a tcp port

$ socat tcp-listen:1234,fork exec:cat # a forking cat service