此属性显示为写入而缓冲的字符数。 缓冲器中可能包含字符串，其编码后的长度是未知的。 因此，此数字仅是缓冲器中字节数的近似值。
This property shows the number of characters buffered for writing. The buffer may contain strings whose length after encoding is not yet known. So this number is only an approximation of the number of bytes in the buffer.
net.Socket has the property that
socket.write() always works. This is to
help users get up and running quickly. The computer cannot always keep up
with the amount of data that is written to a socket. The network connection
simply might be too slow. Node.js will internally queue up the data written to a
socket and send it out over the wire when it is possible.
The consequence of this internal buffering is that memory may grow.
Users who experience large or growing
bufferSize should attempt to
"throttle" the data flows in their program with