Closes the writable side.
Releases the underlying stream lock without closing the stream.
Used when a starttls upgrade swaps the socket: the old writer must relinquish its lock so
the new socket's streams can be locked, without closing the (discarded) old stream.
Writes a chunk of bytes.
Writes s as UTF-8 followed by CRLF.
FramedWriter backed by a WritableStream of bytes.