echo-stream-input-stream, echo-stream-output-stream

echo-stream-input-stream echo-stream → input-stream

echo-stream-output-stream echo-stream → output-stream

echo-stream — an echo stream.

input-stream — an input stream.

output-stream — an output stream.

echo-stream-input-stream returns the input stream from which echo-stream receives input.

echo-stream-output-stream returns the output stream to which echo-stream sends output.