Tēⁿ Kî Hun

blocking socket: 

the program is "blocked" until the request for data has been satisfied. 

non-blocking socket:

Programs that use non-blocking which allows your application to respond to events. For example, when the remote system writes data to the socket, a Read event is generated for the control. Your application can respond by reading the data from the socket, and perhaps send some data back, depending on the context of the data received

Programs that use non-blocking sockets typically use one of two methods when sending and receiving data. The first method, called polling, is when the program periodically attempts to read or write data from the socket (typically using a timer). The second, and preferred method, is to use what is called asynchronous notification. This means that the program is notified whenever a socket event takes place, and in turn can respond to that event. For example, if the remote program writes some data to the socket, a "read event" is generated so that program knows it can read the data from the socket at that point.

-----