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A modem
by email and other radio devices
there is an app called pouncer
BUSEach channel, called a bus, allows the various devices both inside and attached to the system unit to communicate with each other
serial port to communicate between CPU with other devices such as printer
Servers
Servers
To communicate with other people over a long distance.
network
SANs. (Storage Area Networks.)
network interface card
You can connect other devices and allow them to communicate to each other, just like any other local area network.