Socket Overview

• This is chapter 56.
• Sorry people in data comm
• Sockets are bi-directional communications mechanisms.
  • The communicating processes do not need to be related in any way.
  • This means that there is more work in setting them up however.
• fd = socket(domain, type, protocol);
• There are three basic types we will concentrate on.
  • These are called communications domains.
  • AF_UNIX: communication between processes on the same host.
    • This is completely within the kernel.
    • Addresses are the names.
    • Address structure sockaddr_um
  • AF_INET: communications between processes on potentially different hosts, IPV4
  • AF_INET6: IPV6
    • This is kernel, device drivers, ...
    • Address structure
      • IPV4: 32 bit address and 16 bit port
      • sockaddr_in
      • IPV6: 128 bit address and 16 bit port
      • sockaddr_in6
  • He points out that AF stands for Address Family, apparently there are equivalent PF_ which stands for Protocol Family, but this has been abandon.
• But do a quick man 2 socket.
• Each of these can have one of two types we will look at
  • Datagram
  • Stream
• Datagram (UDP or User Datagram Protocol)
  • This is a non-reliable service
    • ie the data may or may not arrive. The protocol does not take care of failed delivery.
    • And may not arrive in order
    • And may have duplicate deliveries.
    • It does not assume a connection, ie the messages are independent.
      • More on this later.
  • Stream Socket (TCP transmission Control Protocol)
    • Connection oriented.
    • Reliable, in order, unique delivery.
    • It is just a stream, no "boundaries" between messages.
  • These are not the only types, Agana man 2 socket
  • Generic Steps
    • Build the socket with socket
    • Bind the socket to an address with bind
    • Wait for a connection to occur with listen
    • Form the connection with connect
    • read/write
    • Close the connection with close