2014-10-16

Network Programming 2014-10-16

2014/10/16 Network Programming Class Note

Byte Order

• Little endian: int -> short is convenient (still implemented in most PCs)
• Big endian: straight forward, hence become main trend (media formats, networking)

          |   |                 Big endian
A ------> |   | 0 1               A  A+1 A+2 A+3
A + 1 --> |   | 0 0             +---+---+---+---+
A + 2 --> |   | 0 0             | 0 | 0 | 0 | 1 |
A + 3 --> |   | 1 0             +---+---+---+---+
          |   |                  A+3 A+2 A+1  A
                                Little endian

• Circuit switching: telephone system
• Packet switching: IP
• Virtual circuit switching: TCP (each packet may not go through same path)

Buffer in Network Programming

Send/receive buffers are normally in 2 KB, 4 KB, or 8 KB size. We use 4 KB for example.

• Define of a successfully write(): write to send buffer, not transmit
  • 3 KB full, write 2 KB => return length of successfully written data, then continue
  • 4 KB full, write 2 KB => blocked until send buffer is available again
• Define of a successfully read(): read from receive buffer as long as data arrive receive buffer (even buffer is not full)

Socket Programming

• htons(): host to network short