When I write data to streams created by socket-make-stream with write-sequence, even the stream was created with the option  :buffering :none, write-sequence still acts as if the stream was still buffered. i.e. I have to call finish-output or force-output to send the data. But write-byte does not have this problem. The code is something as follows:

(setf str (socket-make-stream socket :input t :output t :buffering :none :element-type '(unsigned-byte 8))
        a    (make-array 10 :element-type '(unsigned-byte 8) :initial-element 1))
(write-sequence a str)
(finish-output str)