8Input and Outputπ i
A Racket port corresponds to the Unix notion of a stream
(not to be confused with racket/streamβs streams).
A Racket port represents a source or sink of data, such as a
file, a terminal, a TCP connection, or an in-memory string. Ports
provide sequential access in which data can be read or written a piece
at a time, without requiring the data to be consumed or produced all
at once. More specifically, an input port represents a
source from which a program can read data, and an output
port represents a sink to which a program can write data.