Function serve 

pub fn serve<R, W>(reader: R, writer: W, client: &HttpClient) -> Result<()>
where
    R: BufRead,
    W: Write + Send,

Serves newline-delimited JSON-RPC until reader reaches EOF.

Each message is handled on a fresh synchronous OS thread. Responses are flushed one per line; notifications produce no output.

Errors

Returns an I/O error when stdin cannot be read, stdout cannot be written, or a request thread panics.