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When three or more devices share a communication path, serial-port program-

ming becomes more complicated. Each computer, or node, in the network,

needs to know when it’s OK to transmit and whether to respond to or ignore a

received message. This chapter shows how to ensure reliable and efficient com-

munications in a serial network and how to implement a basic network proto-

col.

 
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One of the first things to decide is how the network will manage its traffic. A

typical network has the following features:

• Each node can send and receive data.


• Only one node transmits at a time.


• Each node recognizes and responds to messages intended for it and ignores
  all others.


• The transmitting node detects when a node didn’t receive a message and
  takes appropriate action.