OSI Model Layers

Application Layer (应用层)
Presentatin Layer （表示层）
Session Layer (绘制层)
Transport Layer （传输层）
Network Layer （网络通讯层）
Data-Link Layer （数据链接层）
Physical Layer (物理层)

Two types of Internet domain sockets:
stream sockets (= TCP sockets)
      provides communication in connected mode
      guarantees reliable data transmission|
      costs time in connection set-up and error checking
datagram sockets(=UDP socket)
      provides communication in connectionless mode
      does not guarantee reliable data transmission
      saves time from connection set-up and error checking

What is byte ordering ?

   The byte order is the order in which bytes are stored to create larger data types such as the int and
   long values

    Two types of byte-ordering in computers:

         little-endian:low-order (less significant) byte first (Intel microprocessor)
          big-endian:high-order (most significant) byte first (Motorola microprocessor)