1. CSC 552 - Advanced Unix Programming, Fall 2015
Wednesday, September 30
TCP and UDP socket system calls

2. Example code ~parson/UnixSysProg/udptcp.fall2015.zip

3. Transmission Control Protocol / Internet Protocol (TCP/IP)
Pipe-like, connection oriented, virtual circuit protocol. (But, a pipe lives inside one machine’s OS.)
Reliable data delivery via sequence numbers, acknowledgments, timeouts, retransmissions
TCP/IP has guaranteed order of delivery.
There is overhead associated with TCP/IP reliability.
Write() data boundaries for sender may differ from read() data boundaries for receiver.

4. TCP/IP Connection Establishment
Server Process Client Process socket() (local endpoint) socket() bind() (IP address + TCP port) listen() (wait for connect) SYN connect() accept() (grant connection request, makes new fd) SYN, ACK read() ACK write() write () ACK read() close() FIN or RST close()

5. User DatagramProtocol / Internet Protocol (UDP/IP)
Discrete, atomic messages from a sender’s sendto() call arrive at a receiver’s recvfrom().
Unreliable data delivery may discard datagrams.
UDP has no guaranteed order of delivery.
There is minimal overhead with UDP/IP.
Sendto() data boundaries for sender do not differ from recvfrom() data boundaries for receiver.
Good medium for media streams where dropped datagrams can be ignored.

6. UDP/IP Connectionless Interaction
Server Process Client Process socket() (local endpoint) socket() bind() (IP address + TCP port) recvfrom() sendto() sendto() recvfrom() close() (closes local endpoint) close() (local)