title: When the new value specified for SO_RCVBUF in setsockopt() will take effect?
body: <p>My query is related to “SO_RCVBUF” option in setsocketopt() api.
  When the new value specified for SO_RCVBUF in setsockopt() will take effect?</p>
  
  <p>I am testing the flow control of TCP/IP and below is my environment. 
  The client program is a slow reader and it has a single socket. 
  To test the flow control, I am reducing the value of SO_RCVBUF to 5000 bytes after establishing the connection and before receiving the data.
  My expectation is that, my server program after sending 5000+ bytes should wait for client to read. But the server program sends the data till ~60000 bytes.
  After that the server program will wait for client to read. Once the client reads ~55000 bytes, then I see the new value of receive buffer (5000bytes) getting utilized.</p>
  
  <p>Is it expected? I guess effect of setsocketopt() should be  immediate. The initial value of receive buffer should not have any effect after setsocketopt().</p>
  
  <p>Regards,
  Prashanth</p>