@Override
                    public int write(final ByteBuffer src) throws IOException {
                        return channel.write(src);
                    }
Usually the last HTTP/1.1 request execution handler in the asynchronous
request execution chain that is responsible for execution of
request/response exchanges with the opposite endpoint.

@since 5.0
httpclient5/src/main/java/org/apache/hc/client5/http/impl/async/HttpAsyncMainClientExec.java